Use of Native Plants and Coir Fiber Logs for Nitrogen Uptake in Waimānalo Stream

Use of Native Plants and Coir Fiber Logs for Nitrogen Uptake in

Waimānalo Stream.

A THESIS SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWAI‘I IN PARTIAL FULFILLMENT OF THE

REQUIREMENTS FOR THE DEGREE OF

MASTER OF SCIENCE

IN

NATURAL RESOURCES AND ENVIRONMENTAL MANAGEMENT

MAY 2009

By Carolyn H. Unser

Thesis Committee:

Greg Bruland, Chairperson

Creighton Litton Traci Sylva

ii

We certify that we have read this thesis and that, in our opinion, it is satisfactory in scope

and quality as a thesis for the degree of Master of Science in Natural Resources and

Environmental Management.

THESIS COMMITTEE

_____________________________________

Chairperson

_____________________________________

_____________________________________

iii

Acknowledgements

I would like to express my sincere appreciation to my advisor, Dr. Greg Bruland,

for direction and guidance throughout this project, as well as, being a constant source of

positive feedback. I also thank Andrew Hood and Kristin Duin, of Sustainable Resources

Group International, Inc. (SRGII), for the opportunity to work with them on this project

and for their guidance and patience in the process. I would also like to express gratitude

to Dr. Creighton Litton and Dr. Traci Sylva for their service as committee members, and

their valuable input on the content and direction of this thesis.

A special thanks to Dr. Dennis Gonsalves, Norma Ross, and Dr. Russell Yost for

their role and support in inspiring me to pursue graduate school. Thanks to Roy Camara,

Pauline Chinn, Guy Porter, Meris Bantilan-Smith, Dana Ogle, Gwen DeMent, Chad

Browning, Christina Speed, Matthew Saunter, Ali‘i Garcia, Matthew Bauer, Peter and

Lisa Opert, Chad Durkin, Margot Chase, Leena Muller, and all the volunteers who have

helped with stream implementation.

I am grateful to Dr. Halina Zaleski for statistical guidance, Rick and Hui Ku

Maoli Ola nursery for their assistance with plants and logistics, Servillano Lamer for

mesocosm assistance and security, Dr. Travis Idol for access to weather station

information, and Pono Pacific, LLC, for their services.

I would like to recognize SRGII and the Hawai‘i Department of Health’s (DOH)

319(h) Clean Water Act Grant for funding this project. Although the research described

in this thesis has been funded by Hawai‘i’s DOH, it has not been subjected to any DOH

review and therefore does not necessarily reflect the views of the Department, and no

official endorsement should be inferred.

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Finally, I would like to thank my family and friends, especially my mom and dad,

and Kenny for their unconditional love and support.

v

Abstract

Many of Hawai‘i’s streams are currently on the State’s 303(d) list of impaired

water bodies for which levels of nutrients and suspended solids exceed that of

Environmental Protection Agency (EPA) allowable loads. Waimānalo Watershed,

located within the Ko’olaupoko region of Oahu, is listed as a top priority watershed for

restoration. The high nitrogen (N) concentration of surface waters was identified as a

priority concern for the middle reaches of both Waimānalo and Kahawai Stream, with N

concentrations being consistently greater in Kahawai Stream. This research investigates

best management practices (BMPs) that can be used to increase N accumulation from

surface water by riparian plants and to enhance stream structure and function.

Specifically, an innovative approach using native sedges planted in coconut fiber coir

logs was first studied in a controlled experimental mesocosm setting and then in a field

experiment with a large-scale installation of pre-planted coir logs along riparian zones of

Waimānalo and Kahawai Streams. While coir logs have been successfully employed in

continental streams for restoration purposes, they have not been used for streams in

Hawai‘i. Identification of appropriate species and the successful installation of pre-

planted coir logs along stream banks have the potential to accumulate N while protecting

plants from high flows for successful root anchoring into stream-bank substrate as the

logs degrade. The following species, Cladium jamaicense, Cyperus javanicus, Cyperus

laevigatus, and Cyperus polystachyos were tested in experimental mesocosms for their

ability to survive in coir log media with exposure to differing N concentrations. It was

hypothesized that the selected species would have significantly different tissue total

nitrogen (TN) concentrations, aboveground biomass, and TN accumulation rates because

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of habitat preference and physiological growth differences among species. A general

linear model (GLM) analysis of variance (ANOVA) revealed that species accounted for

the greatest proportion of variance in tissue TN concentration, aboveground biomass

growth, and accumulation rates. A post hoc test of means demonstrated that C.

jamaicense had substantially higher tissue TN concentration, aboveground biomass

growth, and accumulation rates than the other species under all N levels. It was also

hypothesized that tissue TN concentrations and biomass growth would increase in plants

exposed to elevated N levels. While the data from the mesocosm experiment did not

support this hypothesis, the data from the field installations partially supported the

hypothesis for C. jamaicense as tissue TN concentration, aboveground biomass growth,

and accumulation rates in Kahawai Stream were significantly higher than in Waimānalo

Stream. Results from this study suggest that those attempting to remediate impaired

Hawaiian streams should consider using pre-planted coir logs with native species that

produce abundant biomass and have the ability to store substantial TN in their tissues.

vii

Table of Contents Acknowledgements ............................................................................................................ iii Abstract ............................................................................................................................... v List of Tables ................................................................................................................... viii List of Figures .................................................................................................................... ix List of Abbreviations ........................................................................................................ xii Chapter 1: Introduction and Background ............................................................................ 1

Waimānalo Stream .......................................................................................................... 1 Riparian ecosystems ........................................................................................................ 7 Constructed Wetlands ..................................................................................................... 9 Phytoremediation .......................................................................................................... 10 Native Species ............................................................................................................... 12 Coconut Fiber Coir Logs ............................................................................................... 14 Objectives ...................................................................................................................... 14

Chapter 2: Planted Coir Log Nutrient Addition Experiment ............................................ 18 Introduction ................................................................................................................... 18 Objectives and Hypothesis ............................................................................................ 20 Materials and Methods .................................................................................................. 21 Statistical Analyses ....................................................................................................... 35 Results ........................................................................................................................... 36 Discussion and Conclusions .......................................................................................... 54

Chapter 3: Field Installation of Pre-Planted Coir Logs in Waimānalo Stream ................. 65 Introduction ................................................................................................................... 65 Objectives and Hypothesis ............................................................................................ 68 Materials and Methods .................................................................................................. 69 Statistical Analyses ....................................................................................................... 77 Results ........................................................................................................................... 78

Chapter 4: Discussion and Conclusions ............................................................................ 99 Appendix A. .................................................................................................................... 107 Appendix B. .................................................................................................................... 109 References ....................................................................................................................... 110

viii

List of Tables Table Page

2.1. List of species used for the experiment (in alphabetical order), the status groups to which these species belong, and other important traits. .................................................... 22

2.2. Mean water physiochemical characteristics in the mesocosms as recorded by the YSI probe during nutrient adjustment period January-February (n = 3). ................................. 29

2.3. Results from the combined GLM ANOVA testing mesocosm species tissue TN concentrations from December through May. .................................................................. 39

2.4. A comparison of mean tissue total N concentrations (percent ± standard deviation) in aboveground tissue for the four species over all sampling dates from all three N treatments. [(***) n = 1, (**) n = 2, (*) n = 3]. ............................................................... 43

2.5. Results from the combined GLM ANOVA testing mesocosm species aboveground biomass. ............................................................................................................................ 48

2.6. Total nitrogen accumulation rates (mean ± standard deviation) in June 2008 for different species and treatment mesocosms. The different letters represent the significant differences according to Waller-Duncan K-ratio t test (P<0.05) in the same species (n = 4, n = 3 for C. laevigatus, n = 2 for C. laevigatus in High). ............................................. 51

2.7. Results from the combined GLM ANOVA testing mesocosm species TN accumulation rates. ........................................................................................................... 52

3.1. Mean stream physiochemical characteristics of Kahawai and Waimānalo streams at locations upstream and downstream of remediation site from September 2007 through February 2009 (n = 15). .................................................................................................... 79

3.2. Mean concentration (mg L-1) of Total Nitrogen (TN) and Nitrate- + Nitrite-Nitrogen collected in Kahawai and Waimānalo Streams from September 2007 through February 2009, and compared with the State water quality standards* during the wet and dry season** and during storm event***. ............................................................................... 80

3.3. Results from the combined GLM ANOVA testing mesocosm species tissue TN concentration (%). ............................................................................................................. 83

3.4. Results from the combined GLM ANOVA testing mesocosm species tissue biomass growth (g DW m2). ........................................................................................................... 86

3.5. Results from the combined GLM ANOVA testing mesocosm species tissue TN accumulation rates (g TN m2 y-1). ..................................................................................... 89

A.1. Chemical composition of the Growmore © 10-8-22 Hydroponic Fertilizer hydroponic fertilizer used in the mesocosm experiment. ............................................... 109

ix

List of Figures

Figure Page

1.1. Map of the Hawaiian Islands with the Waimānalo watershed and stream locations on Oahu. ................................................................................................................................... 3

1.2. Map of the land uses in the Waimānalo watershed and stream locations on Oahu. Layer developed with 2004 data from the Hawaii Gap Analysis Program (HI-GAP). ...... 5

2.1. The constructed mesocosm design and dimensions. The photograph on the right-hand side shows the foil covered tubing which diverted reservoir outflow in order to maximize nutrient dispersal in mesocosm. ....................................................................... 24

2.2. Photographs of the low, medium, and high (right to left) concentration meoscosms on Nov. 20, 2007, 1-week after planting (upper photo) and on Jun. 14, 2008, 7 months after planting (lower photo). ............................................................................................. 28

2.3. The mesocosm experimental design. ........................................................................ 31

2.4. Mesocosm coir log planting scheme with a side view of the exposed surface area. . 34

2.5. Total N concentrations (mean ± 1 standard error) among the four species (n = 72 for C. jamaicense and C. javanicus, n = 57 for C. laevigatus, n = 70 for C. polystachyos). Bars with different letters represent significant difference according to Waller-Duncan K-ratio t test (P<0.05). .......................................................................................................... 40

2.6. Total N concentrations (mean ± 1 standard error) among species*treatment effect. Bars with different letters represent significant differences according to the post hoc test of means (P<0.05). ............................................................................................................ 41

2.7. A comparison of tissue N concentration (n = 72, mean ± 1 standard error) in plant aboveground biomass tissue for C. jamaicense across the N treatments (mesocosm). Bars with different letters represent significant difference according to Waller-Duncan K-ratio t test (P<0.05). .................................................................................................................. 42

2.8. Total N concentrations (mean ± 1 standard error) during February 2008. (a.) Species accounted for a significant proportion of variance (F = 23.79, p = < 0.001; n = 12, n = 10 for C. laevigatus), (b.) treatment accounted for a lesser but nonetheless significant proportion of variance (F = 5.4, p = < 0.001; n = 16, n = 15 for high). Bars with different letters represent significant difference according to Waller-Duncan K-ratio t test (P<0.05). .................................................................................................................. 44

2.9. Total TN concentrations (mean ± 1 standard error) of the four plant species over time. (a) Nursery plantings (n = 3) November 2007. (b) Mesocosm December 2008 (n = 12). (c) Mesocosm April 2008 (n = 12, n = 8 for C. laevigatus). (d) Mesocosm June 2008 (n = 12, n = 10 for C. laevigatus). Bars with different letters represent significant difference according to Waller-Duncan K-ratio t test (P<0.05). ...................................... 45

x

2.10. Mean aboveground biomass (mean ± 1 standard error) of the four plant species across the treatments (mesocosms) (n = 4). Bars with different letters represent significant differences according to the post hoc test of means (P<0.05). ....................... 49

2.11. Mean aboveground TN accumulation (mean ± 1 standard error) of the four plant species across the treatments (mesocosms) (n = 4, n = 3 for C. laevigatus). Bars with different letters represent significant differences according to the post hoc test of means (P<0.05). ........................................................................................................................... 53

2.12. Total aboveground biomass (mean ± 1 standard error) across the N addition treatments (n = 15). ........................................................................................................... 60

2.13. This photo illustrates the creeping rhizomatous growth of Cyperus laevigatus observed in some of the mesocoms. ................................................................................. 61

3.1. The Waimānalo Stream reach with coir log layout and experimental log placement............................................................................................................................................ 72

3.2. The Kahawai Stream reach with coir log layout and experimental log placement. . 73

3.3. Rainfall data during the December 2008 storm event. Data obtained from the National Weather Service (NWS) Waimānalo station (HI13). ......................................... 74

3.4. The experimental coir log layout after the December 28, 2008 flood event. ........... 75

3.5. Mean values of Total Nitrogen (TN), Total Dissolved Nitrogen (TDN), and Nitrate+Nitrite-Nitrogen (NO3

—N+NO2--N) from September 2007 through February

2009. Figure A shows results from the Waimānalo Stream section and Figure B shows Kahawai Stream section (n = 2, n = 1 for storm event). ................................................... 81

3.6. Mean total TN concentrations (percent ± 1 standard error) by species (n = 24, n = 16 for C. polystachyos). Bars with different letters represent significant difference according to Waller-Duncan K-ratio t test (P<0.05). ........................................................................ 84

3.7. Mean aboveground biomass (mean ± 1 standard error) of the three plant species. Bars with different letters represent significant differences according to Waller-Duncan K-ratio t test (P<0.05) (n = 24, n = 16 for C. polystachyos). ............................................ 87

3.8. Mean total N accumulation rates (mean ± 1 standard error) by species (n = 24, n = 16 for C. polystachyos). Bars with different letters represent significant difference according to Waller-Duncan K-ratio t test (P<0.05). ....................................................... 90

xi

3.9. Mean values of the three species (mean ±1 standard error) in the two stream sections. (a) Total nitrogen (TN) concentrations. (b)Aboveground biomass. (c) Total nitrogen (TN) accumulation rates. Bars with different letters represent significant differences according to the post hoc LSD test of means (P<0.05). (n = 8 in Waimānalo Stream; n = 16, n = 8 for C. polystachyos in Kahawai Stream) ........................................ 91

A.1. Total daily rainfall (mm) recorded from November 11, 2007 through June 22, 2008.......................................................................................................................................... 107

A.2. Mean daily temperate range (°C) recorded from November 11, 2007 through June 22, 2008........................................................................................................................... 107

A.3. Daily total solar radiation (W/m2) recorded from November 11, 2007 through June 22, 2008........................................................................................................................... 108

A.4. Daily mean relative humidity (%) recorded from November 11, 2007 through June 22, 2008........................................................................................................................... 108

xii

List of Abbreviations ADSC Agricultural Diagnostic Service Center ANOVA Analysis of Variance BMP Best Management Practice CW Constructed Wetland CWA Clean Water Act DOH Department of Health DIN Dissolved Inorganic Nitrogen EPA Environmental Protection Agency GLM General Linear Model LSD Lease Significant Difference MSAL Marine Science Analysis Laboratory N Nitrogen P Phosphorus TN Total Nitrogen TDN Total Dissolved Nitrogen TKN Total Kjeldahl Nitrogen TMDL Total Daily Maximum Load

1

Chapter 1: Introduction and Background

The presence of nutrients such as nitrogen (N) and phosphorus (P) are essential

for healthy surface waters. For example, waterways with adequate N and P support a

diverse assemblage of aquatic organisms such as algae, aquatic plants, insects and fish.

However, increases in the supply of N and P into waterways can promote deleterious

conditions in these ecosystems. One common result of nutrient enrichment is

eutrophication (Nixon 1995; Andersen, Schluter et al. 2006). Eutrophication often results

in a host of undesirable responses that degrade estuaries and coastal waters such as

increased algal production, reduced sunlight penetration into the water column, anoxia,

fish kills, and increased pathogens and toxins (Clement, Bricker et al. 2001; Laws and

Ferentinos 2003). On a global scale, nutrient and sediment pollution have contributed to

the decline of estuaries, seagrass beds, coastal wetlands, coral reefs, and other coastal

ecosystems (Vitousek, Aber et al. 1997; Laws and Ferentinos 2003; Bruland 2008).

Intact freshwater ecosystems, which are vital to human health and economies worldwide,

are rapidly diminishing as a consequence of human manipulations and the scale and

extent of these human impacts on freshwater systems have risen precipitously during the

last two decades (Abramovitz 1996; Vitousek, Mooney et al. 1997).

Waimānalo Stream

The Waimānalo Watershed, located in the Ko’olaupoko region of Eastern Oahu,

drains approximately 16 km2 area into Waimānalo Bay and onto a reef with submerged

margins (KBAC 2002). Waimānalo Stream is the primary drainage for the basin and the

watershed’s only true perennial stream, which stretches about 5.5 km in length. The

2

stream consists of two main tributaries: Kahawai Stream to the southeast and Waimānalo

Stream to the northwest, which merge roughly 0.5 km below the Kalaniana’ole Highway

(Harrigan and Burr 2001; KBAC 2002; Laws and Ferentinos 2003) (Figure 1.1). Unless

otherwise noted, the term “Waimānalo Stream” will include both Waimānalo and

Kahawai tributaries.

Waimānalo translates to potable, or sweet water in the native Hawaiian language

(Pukui and Elbert 1986). Unfortunately, in a recent report issued by the Hawai‘i State

Department of Health (DOH), Waimānalo Stream was described as an impaired, highly-

altered waterway that no longer functions as a natural stream as sediments and nutrients

from the watershed enter the stream at a rate faster than they can be assimilated (HIDOH

1998; Harrigan and Burr 2001; KBAC 2002; Laws and Roth 2004).

Waimānalo Stream was first listed as an impaired water body in Hawai‘i’s 1998

Clean Water Act (CWA) 303(d) List (HIDOH 1998; KBAC 2002). In a standard

response to the official priority listing, a Total Maximum Daily Load (TMDL)

assessment for Waimānalo Stream was conducted (Harrigan and Burr 2001). This

assessment was prepared by the U.S. Environmental Protection Agency (EPA) and DOH

to determine the maximum amount of pollutants that can enter Waimānalo Stream

without violating the State’s Water Quality Standards. The TMDL identified the reaches

of Waimānalo Stream where sediments and nutrients exceeded the stream’s capacity for

assimilation and recycling of pollutants. The largest concern in the TMDL was the need

for substantial reduction of nitrate (NO3-) loads in the middle segments of the watershed

(Harrigan and Burr 2001). Following this assessment, a report

3

Figure 1.1. Map of the Hawaiian Islands with the Waimānalo watershed and stream locations on Oahu.

4

for implementation recommendations was ordered (USEPA 2001). This implementation

report described in further detail Waimānalo Stream’s many problems, including poor

water quality, degraded habitat, and altered flow regimes. This report also identified

potential ways to reduce the inputs of pollutants to the stream and ways to improve the

stream’s ability to assimilate these pollutants. Since placement on the EPA’s 303(d) list

of impaired water bodies of Hawai‘i, both local residents and environmental groups have

recognized the need for restorative action to address point and nonpoint source pollutants

effecting the health of Waimānalo Stream.

Many factors have contributed to the degradation of Waimānalo Stream’s

ecosystem. Urban development and land-use changes over the last century have

drastically altered the stream’s waterways and landscapes resulting in a shift leading to

the degradation of natural ecosystem functions and processes (Laws, 2003; KBAC,

2002). The primary land use for the two tributaries includes a high proportion of

agriculture and intensified development along Kahawai Stream, whereas Waimānalo

Stream’s tributary mainly consists of some agriculture with the upper forested

conservation area (Figure 1.2). Past and present water quality data has been consistent

when showing Kahawai tributary to contain higher surface water N concentrations than

Waimānalo tributary (Laws and Ferentinos 2003)(Table 3-2). Modifications of

Waimānalo Stream habitat include the hardening of the stream channel bed, reduction of

riparian buffer zones to accommodate flood control, and increased run-off from urban

development (Laws and Ferentinos 2003; Laws and Roth 2004). Erosion of stream

banks, including the toe area, is one of the major contributors to sediment pollution in

streams and near shore marine waters of Hawai‘i (USEPA 2004) and Waimānalo Stream

5

Figure 1.2. Map of the land uses in the Waimānalo watershed and stream locations on Oahu. Layer developed with 2004 data from the Hawaii Gap Analysis Program (HI-GAP).

6

is no exception to this general trend (USEPA 1998). Other contributors of stream

pollution include surface runoff generated from agricultural and residential areas,

leaching of nutrients from fertilizers, cess pools, and animal wastes into the groundwater

and eventually into the stream systems. These pollutants are then transported

downstream where they are either deposited in or along streams, or in receiving marine

waters. Land-based sources of pollutants, such as sediment, nutrients, and heavy metals,

are one of several factors threatening the quality of coral reef ecosystems in Hawai`i

(USEPA 2001; USEPA 2004). Poor-quality lotic habitat with non-existent or degraded

riparian buffer zones generally exacerbate the negative effects of residual nutrient

concentrations by reducing riparian uptake of nutrients and diminishing filtration rates

(Sabater, Butturini et al. 2000; Laws and Roth 2004; Ghermandi, Vandenberghe et al.

2009). Management and continued monitoring of these pollutants is important for

sustaining Hawai‘i’s terrestrial and aquatic habitats, as well as ensuring the future of

healthy aquifers.

The practice of restoring degraded ecosystems draws on both the intellectual

framework of ecological theory and the application of the scientific method in restoration

ecology (Palmer, Falk et al. 2006). This project attempts to bridge the gap between

structural attributes that can be easily measured and ecosystem function (Zedler 2000).

Past demonstration projects at Waimānalo Stream have employed bioengineering

techniques for the protection of stream banks (HuiKuMaoliOla 2002). This project will

be guided by the State’s initiatives to implement BMPs, will build upon past remediation

efforts, and will utilize principles from constructed wetlands and phytoremediation for N

uptake. Successful establishment of vegetation in riparian areas can significantly

7

decrease sediment loads generated from these areas during storm flows (USEPA 2001).

Native plantings can potentially alien vegetation that decrease stream habitat quality and

often clogs channel ways (Laws and Ferentinos 2003). The use of coconut coir fiber logs

for stream toe protection will be expanded to include the development of pre-planted logs

to decrease the time that the vulnerable area of the stream banks are exposed to erosion

during a restoration project and speed up the establishment of native vegetation in the

riparian zone. Measurement of plant tissue N and biomass can provide a simple index of

N removal efficiency by restored wetlands (Reddy and DeLaune 2008). The effects of

nutrient application on tissue chemistry and biomass will be measured and compared

among species and across different sites

Riparian ecosystems

For purposes of this project, riparian ecosystem will be defined as follows:

A vegetated ecosystem along a water body through which energy,

materials, and water pass. Riparian areas characteristically have a high

water table and are subject to periodic flooding and influence from the

adjacent water body. These systems encompass wetlands, uplands, or

some combination of these two landforms. They will not in all cases have

all the characteristics necessary for them to be also classified as wetlands

(USEPA 2005).

The functions of wetlands and riparian areas include water quality improvement, stream

shading, organic matter supply, flood attenuation, shoreline stabilization, ground water

exchange, and habitat for aquatic, semi-aquatic, terrestrial, migratory, and rare species

8

(Sabater, Butturini et al. 2000; Brennan 2005; USEPA 2005). Ecologically-intact

riparian areas naturally retain and recycle nutrients, modify local microclimates, and

sustain broadly-based food webs that help support a diverse assemblage of fish and

wildlife (NRC 2002). In recent decades, the rates of urbanization and recreational

development along waterways have accelerated and greatly altered many of the nation’s

riparian areas (NRC 2002).

Riparian areas have been studied intensely in recent years because of their critical

functional relationships to stream and wetland ecosystems (Brennan 2005). Large-scale

studies by Likens (1970), Peterson (2001), and Bernhardt et al. (2002) showed that the

loss of wetlands and riparian areas have eliminated important natural N sinks where

much of the entering nitrate is consumed via denitrification. Both Sabater (2000) and

Ghermandi (2009) found, in studies looking at riparian vegetation removal, that

disturbances in small shaded streams have indirect effects on in-stream ecological

features that may lead to changes in stream nutrient retention efficiency. Restoration of

such areas and the construction of artificial wetlands have been shown to be effective at

reducing the transfer of N from agricultural land to adjacent waterways (Vitousek, Aber

et al. 1997). Riparian plantings often act as a sink for nutrients from agricultural field

runoff because they can accumulate some of the nutrients before they enter nearby

waterways (Pinay, Fabre et al. 1992). In Spain, a restored wetland treating agricultural

runoff showed that emergent macrophytes accumulated between 20 and 100 mg N

m−2d−1, which accounted for between 66-100% of the inflowing dissolved inorganic N

(Comín, Romero et al. 1997).

9

Constructed Wetlands

Constructed wetlands (CWs) are engineered systems that have been designed to

utilize the natural processes of wetland vegetation, soils, and their associated microbial

communities for hydrologic and water quality restoration and for mitigating wetland

habitat loss (Mitsch and Gosselink 2007; Vymazal 2007). Constructed wetlands have

become a widely-accepted and cost-efficient way to create a “natural” environment in

which to “clean” polluted waters. The principles and practices behind creating or

restoring a wetland are based on wetland science and ecological design/engineering

(Todd and Todd 1993; Mitsch and Gosselink 2007). Wetlands remove aquatic pollutants

through a variety of biological, physical, and chemical processes. When compared to

unplanted controls, the presence and type of plants in CWs made a significant difference

in the enhancement of N removal efficiency (Gersberg, Elkins et al. 1983; Gersberg,

Elkins et al. 1986; Tanner, Clayton et al. 1995a; Tanner, Clayton et al. 1995b; Bastviken

2006).

Ideally, CWs are designed to maximize removal of a specific pollutant or groups

of pollutants (Horne 2000). For this project, accumulation of N by plants is the primary

focus. In utilizing the concepts of CWs along the riparian banks of Waimānalo Stream,

the selection of species, design, installation method, and mitigation success become

important factors. A quantitative study of native phreatophytes1 for N assimilation will

improve the ability to select the most appropriate species for restoring riparian

ecosystems in Hawai‘i.

1Phreatophytes are plants whose roots are in direct contact with water in vadose zone.

10

Phytoremediation

Phytoremediation is the use of photoautotrophic plants to partially or substantially

remediate contaminated soils, sediments, and water (Cunningham, Shann et al. 1997;

Horne 2000; USGS 2006). Plants and associated microorganisms can degrade,

accumulate, absorb, transform, or immobilize pollutants, thus limiting their spread in the

environment (Pivetz 2001; Vymazal 2007). Restoring riparian vegetation along

Waimānalo stream for the purpose of reducing excessive surface water N will rely on the

phytoremediation capabilities of these riparian plants.

Phytoremediation takes advantage of natural metabolic processes mediated by

solar energy and is a cost-effective alternative to the civil and chemical engineering

technologies developed over the past 20 years (Cunningham, Shann et al. 1997; Horne

2000). Phytoremediation has also shown promise to accumulate pollutants with a higher

rate and efficiency when compared to conventional remedial technologies (Cunningham

and Ow 1996; Terry and Baneulos 2000; Erakhrumen 2007). Although research differs

on the significance of plant assimilation in nutrient removal (Stottmeister, Wießner et al.

2003), data on N transport in CWs suggest that plant uptake is effective at maximizing N

storage and transformation (Tanner, Clayton et al. 1995b; Tanner 1996; Tanner 2001).

To understand the role of plants in the N treatment process, it is important to

consider the role of phreatophytes in the landscape. When comparing the effectiveness of

an ecosystem process, such as N uptake and retention, phreatophytes are only one part of

a complex system. The pollutant removal functions associated with wetlands and

riparian area vegetation combine the physical process of filtering and the biological

processes of nutrient uptake and denitrification (USEPA 2005). Nitrogen reactions in

11

wetlands effectively process inorganic N through nitrification and denitrification,

anammox, ammonia volatilization, and plant uptake (Reddy and DeLaune 2008).

Nitrogen uptake (assimilation) by plants refers to a variety of biological processes that

convert forms of organic and inorganic N into organic compounds that serve as building

blocks for the cells and tissues of plants (Vymazal 2007).

Nutrient concentrations in plant biomass have been widely used to assess the

availability of nutrients to plants and the degree to which particular nutrients are limiting

for plant growth. The Nitrogen concentration in plant tissue is highly variable and is

dependent on age of the plant, N availability and form (i.e. ammonium-N, nitrate-N),

genetic ability of plant to assimilate N, soil type, and environmental condition (Güsewell

and Koerselman 2002; Reddy and DeLaune 2008). Both, Boyd (1970; 1978) and

McJannet (1995) observed significant interspecies variation in nutrient concentrations

among wetland plants with similar ecological growth habits when grown in different

nutrient levels and under identical soil and nutrient conditions. Past studies reveal a

range of tissue N values when comparing emergent wetland plants. For example, a

review of studies on aquatic plants in the United States reported percent N concentration

(% dry weight) in plant tissue to range from 1.37- 2.87 (Boyd 1970). Another study of

wetland plants from in Canada reported mean tissue N concentration to range from ~ 0.7-

2.2 %. Tanner (1996) and Greenway (1997) found aboveground plant tissue N

concentrations in wetland plants from New Zealand and Australia to range from ~ 0.6

and 3.2 % which was similar to Xu’s (2006) range of 1.9 and 4.7 %.for wetland plants in

China.

12

Tissue N concentration is directly related to the amount of available N in water

and soil (Reddy and DeLaune 2008), and has been shown to increase with increased

amounts of applied nutrients (Xu, Yan et al. 2006). The nutrient use efficiency of

vegetation and the C:N ratio of the plant litter generally decreases with increased nutrient

loading (Reddy and DeLaune 2008), and a negative relationship between percent N and

whole-plant biomass has been observed for aquatic macrophytes (Polisini and Boyd

1972; McJannet, Keddy et al. 1995). High levels of nitrate can be stored or translocated

from tissue to tissue without deleterious effects, however this can be harmful to humans

or livestock if the plant material or water with high nitrate concentrations are consumed

in a condition known as methemoglobinemia (Taiz and Zeiger 2002).

A central goal in restoration ecology is to predict the outcomes of specific

restoration actions, and to meet projected objectives such as maximizing removal of a

specific pollutant or groups of pollutants (Zedler 2000; Zedler and Callaway 2000). In

order to evaluate and monitor the success of a created riparian system, a better

understanding of the role plants play in N accumulation and assimilation will enhance

stream management and remediation efforts. Also, should excessive N in stream waters

adversely affect the structure and function of stream ecosystems, a set of guidelines could

be developed for resource managers when conserving and restoring riparian zones for

efficient N accumulation.

Native Species

The isolation of the Hawaiian archipelago has resulted in the development of

unique native flora and fauna. Biologists divide native plants into two groups, those that

13

are endemic and those that are indigenous (Abbot 1992). The term endemic refers to

plants only occurring in the Hawaiian Islands before human arrival; whereas the term

indigenous is used strictly to describe plants occurring both naturally in the Hawaiian

Islands and somewhere outside the Hawaiian Islands before human arrival (Erickson and

Pottock 2006).

Native species are an integral part of local ecosystems and support biodiversity

and provide habitat for other native species such as fish, insects, and birds. Native plant

species typically thrive without a lot of maintenance, and often require considerably less

water and chemical pesticides. Invasive nonnative plants can contribute directly to the

loss of ecosystem services, or interfere with restoration goals (D'Antonio and Chambers

2006). The elimination or reduction of shade provided by riparian vegetation in

Waimānalo Stream has encouraged the growth of channel-clogging California grass

(Brachiaria mutica), wild sugarcane (Saccharum officinarum), and other nonnative

vegetation that takes up water and nutrients, and traps sediments (Laws and Roth 2004).

Selecting for native plants that will survive and restore riparian functions requires an

ecosystem perspective (Ehrenfeld and Toth 1997), that encompasses the current state of

Waimānalo stream. Plants in the riparian zone of this stream need to be able to withstand

periods of low flow and intense episodic periods of high flow (Tomlinson and DeCarlo

2003), and ideally will have physiological adaptations for removing N loads from this

stream.

14

Coconut Fiber Coir Logs

Coconut coir geo-textile logs are made from 100% natural coconut coir fiber and

are bound by coconut coir polyethylene netting. Coir fibers are found between the husk

and the outer shell of the coconut. Coir logs have been used for toe stabilization along

stream banks, helping to both provide energy absorption and habitat for wetland species

(Army 2006). Coir logs can improve water quality and aesthetics with the use of

emergent aquatic plants (phytoremediation) and can also improve non-point pollution

control by intercepting sediment and associated pollutants coming into the stream from

overbank areas (Allen and Leech 1997). Roth’s (2005) study of biofilters for wastewater

treatment systems used five different media, (coral rubble, blue stone, lava rock,

geotextile, and coconut coir) and found that coconut fiber had a significantly higher

dissolved inorganic nitrogen (DIN) removal rate than the other four treatments. Although

pre-planted logs have been successfully used in the continental U.S., this technique has

neither been demonstrated with Hawaiian plants nor under the highly variable flow rates

found in Hawai‘i. To determine whether coir logs are appropriate for Hawai‘i there are

important bioengineering factors that need to be considered, such as proper assessments

of the site and construction design (Allen and Leech 1997).

Objectives

The overall objective of this project was to identify candidate native sedge species

for stream phytoremediation and to demonstrate the use of pre-planted fiber coir logs for

native plant restoration in two Hawaiian streams. An experimental phase was used to

determine the ability of various native plant species to establish in a coconut coir

15

medium, grow at varying N levels, and to quantify assimilation of N in plant biomass.

The second field installation phase was then used to test the installation of coir logs in an

actual stream environment and compare results of the stream with those of the

experimental phase. Linking these phases together in one project provides an intellectual

framework for restoration and offers the opportunity to test and expand theories to

improve the quality and effectiveness of such remediation efforts in Hawai‘i.

Both chapters of original research, the first dealing with the planted coir log N

addition experiment, and the second with the field establishment, have their own specific

objectives. Details regarding the scientific background behind these objectives and

hypotheses will be presented in the introductions of their respective chapters. The

following is an outline of the thesis chapters, objectives, and hypotheses.

Chapter 1: Introduction

Chapter 2: Planted Coir Log Nutrient Addition Experiment

Objective 2-1: Select native wetland/riparian plant species (Cladium jamaicense Crantz,

sawgrass [‘Uki], Cyperus javanicus Houtt, Java sedge [Ahu’awa], Cyperus laevigatus L.,

smooth flatsedge [Makaloa], and Cyperus polystachyos, manyspike flatsedge [Kiolohia])

for their suitability for restoration using a set of pre-determined criteria including native

status, potential ability to grow on coir logs, ease of maintenance, and commercial

availability (full criteria listed under methods).

Objective 2-2: Determine success of coconut coir logs as a medium for plant

establishment prior to field installation.

16

Hypothesis 2-1: Native wetland/riparian plant species will be able to establish, survive,

and develop on coconut coir medium.

Objective 2-3: Expose selected species to varying levels of N (in the form of ammonium

nitrate in surface water) and compare their tissue TN concentration, aboveground

biomass, and TN accumulation rates.

Hypothesis 2-2a: The individual species selected will have significant differences in

tissue TN concentration, aboveground biomass, and TN accumulation rates. Cladium

jamaicense will have higher tissue TN concentration, aboveground biomass, and TN

accumulation rates, followed by C. javanicus, C. javanicus, and C. laevigatus, as habitat

preferences and physiological growth traits differ among species. Cladium jamaicense is

an obligate wetland species, found in resource-poor wet sites with heights of 1-3 m.

Cyperus javanicus is a facultative wetland species, found in resource-rich marsh areas

with heights of 0.4-1.1 m. Cyperus laevigatus is an obligate wetland species, found in

resource-rich coastal edges with heights of 0.2-1 m. Cyperus polystachyos is a

facultative wetland species, found in variable wet and dry soils, with heights of 0.25-0.9

m (Fetters and Van Dyke 1996; Erickson and Pottock 2006).

Hypothesis 2-2b: Within species, tissue N concentration will increase with exposure to

increasing N addition treatments.

Chapter 3: Field Establishment of Planted Coir Logs in Waimānalo Streams

Objective 3-1: Monitor nitrate, ammonium, and total dissolved N from Waimānalo and

Kahawai streams.

17

Objective 3-2: Install and monitor coir logs planted with native species along 92 meters

(m) of each stream.

Hypothesis 3-1: Plants in coir logs of Kahawai stream will have higher tissue N

concentration and aboveground biomass than plants in coir logs of Waimānalo stream as

Kahawai stream has consistently higher surface water N levels than Waimānalo stream.

Chapter 4: Conclusions

18

Chapter 2: Planted Coir Log Nutrient Addition Experiment

Introduction

For over a decade, Waimānalo Stream has remained on Hawai‘i’s 303(d) listing of

impaired waterways which have sediments and nutrients in excess of allowable loads

(USEPA 1998; Harrigan and Burr 2001; HIDOH 2006). Flow diversion, habitat damage,

and stream channel modifications of Waimānalo Stream have resulted in a highly-

impaired condition, in which this system “no longer functions as a stream” (Harrigan and

Burr 2001; Laws and Ferentinos 2003). A mandated TMDL report for Waimānalo

stream identified the need for substantial reduction of surface water nitrate (NO3) loads in

the middle segments of the watershed (Harrigan and Burr 2001). Harrigan (2001) went

on to say that “regardless of how many BMP’s are implemented for sediment and nutrient

control, significant improvement in the water quality of Waimānalo Stream will be

difficult to achieve unless in-stream standards for flows are set to increase the base flow,

and stream channels and riparian wetlands are at least partly restored to their natural

form and function.”. This chapter addresses the major environmental concerns for

Waimānalo stream, as outlined in the TMDL and subsequent reports, by identifying

candidate species for phytoremediation of the riparian zone in order to restore the

functionality of this stream.

Studies have suggested that using plants for phytoremediation in stream

restoration projects helps to improve and potentially enhance the ecological functioning

and aesthetic values of degraded streams (Brennan 2005; Greenway 2005). While some

19

studies have quantified inorganic contaminant uptake by wetland species (McJannet,

Keddy et al. 1995; Tanner 1996; Greenway 1997; Tanner 2001; Browning 2003;

Bastviken 2006; Xu, Yan et al. 2006), few have focused on Hawaiian species (Van-Dyke

2001). Nitrogen uptake by plants is defined as the amount of N that is assimilated in the

aboveground and belowground portions of a plant; and is directly related to the amount of

available N in water and soil (Reddy and DeLaune 2008). Nutrient concentrations in

plant biomass have been widely used to assess the availability of nutrients to plants and

can differ widely among species even when experiencing the same nutrient availability

(McJannet, Keddy et al. 1995; Güsewell and Koerselman 2002).

Constructed riparian wetlands along stream banks utilize the physical, biological

and chemical processes and functions of a natural wetland to improve water quality

(Browning 2003). Experiments carried out in constructed wetlands or the controlled

environment of mesocosms, are designed with the goal of mimicking the living world and

can often provide useful information about rates of nutrient uptake (Todd and Todd 1993;

Tanner 1996; Tanner 2001; NOAA 2009). This project used constructed mesocosms

designed to approximate the natural conditions of Waimānalo stream and exposed

candidate plant species to varying levels of N inputs in a replicated experimental setting.

Several native Hawaiian sedge species were selected and grown hydroponically using a

coconut coir log media. This coir log medium has often been used outside of Hawai‘i for

bank stabilization and stream revegetation (Allen and Fischenich 1999), but no studies

have been conducted in Hawai‘i with species native to the Hawaiian archipelago.

20

Objectives and Hypothesis

The specific objectives and hypotheses of this chapter are outlined below.

Objective 2-1: Select native wetland/riparian plant species (Cladium jamaicense Crantz,

sawgrass [‘Uki], Cyperus javanicus Houtt, Java sedge [Ahu’awa], Cyperus laevigatus L.,

smooth flatsedge [Makaloa], and Cyperus polystachyos, manyspike flatsedge [Kiolohia])

for their suitability for restoration using a set of pre-determined criteria including native

status, potential ability to grow on coir logs, ease of maintenance, and commercial

availability (full criteria listed under methods).

Objective 2-2: Determine success of coconut coir logs as a medium for plant

establishment prior to field installation.

Hypothesis 2-1: Native wetland/riparian plant species will be able to establish, survive,

and develop on coconut coir medium.

Objective 2-3: Expose selected species to varying levels of N (in the form of ammonium

nitrate in surface water) and compare their tissue TN concentration, aboveground

biomass, and TN accumulation rates.

Hypothesis 2-2a: The individual species selected will have significant differences in

tissue TN concentration, aboveground biomass, and TN accumulation rates. Cladium

jamaicense will have higher tissue TN concentration, aboveground biomass, and TN

accumulation rates, followed by C. javanicus, C. javanicus, and C. laevigatus, as habitat

preferences and physiological growth traits differ among species. Cladium jamaicense is

an obligate wetland species, found in resource-poor wet sites with heights of 1-3 m.

Cyperus javanicus is a facultative wetland species, found in resource-rich marsh areas

with heights of 0.4-1.1 m. Cyperus laevigatus is an obligate wetland species, found in

21

resource-rich coastal edges with heights of 0.2-1 m. Cyperus polystachyos is a

facultative wetland species, found in variable wet and dry soils, with heights of 0.25-0.9

m (Fetters and Van Dyke 1996; Erickson and Pottock 2006).

Hypothesis 2-2b: Within species, tissue N concentration will increase with exposure to

increasing N addition treatments.

Materials and Methods

Species Selection

The selection of species for use in remediation projects is generally based on the

goals of the project (Zedler 2000; Zedler and Callaway 2000; D'Antonio and Chambers

2006). Based on our project objectives, candidate species suitable for use needed to meet

the following criteria:

1. Native status (Erickson and Pottock 2006), 2. Wetland indicator status (Erickson and Pottock 2006), 3. Potential ability to establish roots within and grow on coconut fiber coir logs, 4. Pollutant uptake (Van-Dyke 2001), 5. Stream hydraulic tolerance (Erickson and Pottock 2006), 6. Ease of maintenance (Wagner, Herbst et al. 1990; Brimacombe 2002), 7. Wastewater tolerance (FLC 2001; Van-Dyke 2001; Paquin, Campbell et al.

2004; HuiKu 2008), 8. Commercial/Local availability (Barboza 2007).

Based on these criteria, the four species selected were: Cladium jamaicense, Cyperus

javanicus, Cyperus laevigatus, and Cyperus polystachyos (Table 2.1). Selected species

had been mentioned in literature related to constructed wetlands, have been used in

erosion control projects in Hawai‘i, and/or have been recommended by experts in the

fields of native plant propagation, ecosystem restoration, constructive wetland

22

Table 2.1. List of species used for the experiment (in alphabetical order), the status groups to which these species belong, and other important traits.

Cladium jamaicense

Cyperus javanicus

Cyperus laevigatus

Cyperus polystachyos

Hawaiian name 'uki ahu'awa ehu'awa, makaloa kiolohia Common name Saw grass Java sedge Smooth Flat sedge Manyspike flatsedge Native status2 Indigenous Indigenous Indigenous Indigenous Wetland indicator status2 Obligate Facultative Obligate Facultative Coir log potential N/A N/A N/A N/A Pollutant uptake8 N/A N/A High N/A Stream hydraulic tolerance2

N/A

Media-less/Root submersion

Media/Near water

Moist areas/Root submersion

Ease of maintenance1,9 N/A Low maintenance Low maintenance Low maintenance Wastewater tolerance3,4,5,6,8 High High High Medium Commercial/Local availability7

Yes

Yes

Yes

Yes

1Brimacombe (2002)

2Erickson and Puttock (2006). 3Farmers Livestock Cooperative (2001) 4Hui Ku Maoli Ola (2008) 5Lissner, Mendelssohn et al. (2003) 6Paquin, Campbell et al. (2004) 7Rick Barboza (2007) 8Van-Dyke (2001) 9Wagner, Herbst et al. (1990)

23

implementation, and cultural practices. Data were not always available for listed criteria

and attempts were made to best fit descriptions with criteria objectives.

Experimental Site

In October and November of 2007, grow box mesocosms were constructed at the

University of Hawai‘i Mānoa’s Mauka Campus on the island of Oahu (21°18'19.70"N,

157°48'37.40"W). Experiments were carried out over the winter and spring (11

November 2007 to 14 July 2008) during which time the average daily temperature ranged

from 20.4 to 26.4 °C. The mesocosms were located in an open environmental situation,

with an Onset Computer HOBO H21 Micro2 weather station located on site (Appendix

A).

Wetland Mesocosm

The four selected wetland plant species were exposed to different concentrations

of N though a cyclical hydroponic system. Specifically, three replicate mesocosms were

constructed using plywood frames which measured 2.5 m x 1.2 m x 0.3 m and were

double-lined with high density 6 mm polyethylene sheets (Figure 2.1). An irrigation

reservoir, made from 98 Liter plastic garbage containers (~81 cm height x ~46 cm

diameter), was hydraulically connected to the mesocosms. The reservoirs outflow was

fitted with T-pipe to better disperse reservoir water to both sides of mesocosm. The

2 All the weather station components were from Onset Computer (www.onsetcomp.com). The datalogger was a HOBO H21 Microstation. The temp/RH sensor was a S-THA temp/RH smart sensor. The tipping bucket rain gauge sensor was a S-RGA rain gauge smart sensor. The light sensor was a S-LIB silicon pyranometer.

24

Figure 2.1. The constructed mesocosm design and dimensions. The photograph on the right-hand side shows the foil covered tubing which diverted reservoir outflow in order to maximize nutrient dispersal in mesocosm.

25

mesocosms had a slight downward slope and an electronic aquarium pump at the lower

end that conveyed effluent water back to the irrigation reservoir through clear plastic

tubing. This tubing was wrapped with aluminum foil wherever it was exposed to sunlight

in order to minimize algal growth. Because this experiment was exposed to weather

elements, and in order to keep the logs from being fully inundated during rain events, the

mesocosms were filled to a water depth of 0.15 m and were maintained at that level by a

1.9 cm drainage pipe located at the lower end of each box.

Water and Nutrient Additions

The flow rate (L day-1) was estimated using the “bucket stopwatch” method.3 In

this case, an empty 7.57 liter bucket was placed at the outflow of the reservoirs and the

time required to fill the bucket was recorded with a stopwatch. The water flow rate

through the systems was restricted by the output range of the reservoir nozzle, the 436.1

m3 d-1 electric pumps, and the approximate 38 – 45 Liter reservoir holding water head

needed to meet the reservoir outflow of 327 m3 d-1.

The selected species were tested to determine their ability to survive and grow in

the impaired environmental conditions of Kahawai and Waimānalo Streams. The first

baseline water quality samples were collected from Kahawai and Waimānalo Streams

and used to characterize the in-situ conditions to be replicated in the mesocosm study.

Stream sampling began in September 2007 and continued throughout the project on a

quarterly basis. Water quality sampling results from this study were compared to

published water quality data for Waimānalo stream and followed similar patterns

3 The bucket stopwatch method involves recording the amount of time required to fill a container of known volume.

26

(Harrigan and Burr 2001; Laws and Ferentinos 2003; Laws and Roth 2004). On average,

the total dissolved nitrogen (TDN) concentration for the Kahawai Stream following a rain

event was around 4-5 mg L-1, whereas, average concentrations during base-flow ranged

between 6-8 mg L-1 (Laws and Ferentinos 2003).

A hydroponic fertilizer4 (Appendix B) was used as a baseline nutrient solution to

ensure optimal plant growth (Güsewell and Koerselman 2002). To meet the minimal

plant nutrient requirements, this fertilizer was added with a concentration of 60 mg TN L-

1, which was half of Grow More’s © recommended dose and approximately half the

recommended fertilizer rate for hydroponic lettuce in Hawai‘i (Valenzuela, Kratky et al.

2006). A literature search found that studies of constructed and restored wetlands used a

broad range of nutrient concentrations; for example, overall means ranged from ~13 mg

TN L-1 (Greenway 1997) to over 98 mg TN L-1 (Tanner 1996) and ~108 mg Total

Kjeldahl Nitrogen (TKN) L-1 (FLC 2001).

This project worked within the constraints of the hydroponic system and manual

additions which proved to be a challenge during the first few months. Although the

initial baseline concentration was 60 mg TN L-1, this quickly dropped to an average of 14

mg TN liter-1 after the first week and 1.8 mg TN L-1 after the second week due to rapid

plant uptake. Complications with nutrient additions during the initial phase of the

experiment resulted in eutrophic conditions during the first month and prompted

adjustments of baseline concentrations during the first two months and until a better

understanding of the nutrient dynamics in the mesocosm systems was attained.

Mesocosms were initially filled with tap water and baseline nutrient fertilizer for a

1-month plant acclimatization period. After this period, ammonium nitrate was added to 4 Growmore © 10-8-22 Hydroponic Fertilizer

27

increase the aqueous nitrate in the second and third boxes by 4 mg L-1 and 8 mg L-1,

respectively, to reflect an intermediate and high range of N concentrations for the stream.

The two forms of N generally used for assimilation by plants are ammonia- and nitrate-N

(Vymazal 2007). Because ammonia N is more reduced than nitrate, it is the preferable

source of N for assimilation (Kadlec and Knight 1996).

Mesocosm water was changed every two weeks by completely emptying and

refilling each mesocosm with tap water, after which both the baseline hydroponic

fertilizer and the ammonium nitrate additions were administered into the reservoirs.

During the last three months, ammonium nitrate was re-administered at weekly intervals

due to water samples signaling a significant decrease in available aqueous N after only a

week, likely due to the increased plant biomass (Figure 2.2).

Mesocosm Sample Collection and Laboratory Analysis

Water samples from the mesocosms were collected in 50-mL plastic centrifuge

tubes and immediately put in an ice chest. Physical and chemical properties of the water

in the mesocosm, such as pH, temperature, etc., were closely monitored using a handheld

YSI Model 556 Multi probe system (YSI Instruments, Yellow Springs, OH) to ensure no

major differences occurred across the treatments. Mean characteristics of the grow box

water can be found in Table 2.2. Water samples were sent to the Marine Science

Analytical Lab (MSAL) at UH Hilo to be analyzed for total dissolved nitrogen (TDN),

nitrate+nitrite nitrogen (NO3-N + NO2--N) through the use the ASTM Method D5176

(ASTM 1995), and ammonium nitrogen (NH4-N). Quality Assurance/Control water

samples were collected from the mesocosms at 24 hours, one week, and two weeks

28

Figure 2.2. Photographs of the low, medium, and high (right to left) concentration meoscosms on Nov. 20, 2007, 1-week after planting (upper photo) and on Jun. 14, 2008, 7 months after planting (lower photo).

29

Table 2.2. Mean water physiochemical characteristics in the mesocosms as recorded by the YSI probe during nutrient adjustment period January-February (n = 3).

Mesocosm

Parameter Control Intermediate High

Dissolved Oxygen (mg L-1) 4.35 3.81 3.63

Temperature (oC) 23.89 24.19 23.74

pH 7.19 7.12 7.07

Conductivity (us cm-1) 0.77 0.70 0.75

Total Dissolved Solids (g L-1) 0.50 0.46 0.49

Salinity (ppt) 0.37 0.34 0.37

30

following the addition of baseline and nutrients. The 24-hour sample was used to

measure the estimated calculation of initial N concentrations derived via mass volume

calculations. The one and two week samples were used to quantify how concentrations

in the mesocosms changed over time.

Experimental Procedures

The three mesocosms were designed to mimic the toe area of Waimānalo Stream

where pre-planted coconut coir logs were scheduled to be installed. The hydroponic

mesocosm environment was used to investigate how the four native plant species would

respond to being grown in a coconut coir log media within different surface water N

levels. Due to lack of immediately available material for the mesocosm phase, woven

coconut coir matting was obtained which was then rolled into logs and tied off with

polyethylene string. The coir logs measured 2.13 m long with a 25 cm diameter and were

placed vertically into each mesocosm (Figure 2.3). Three of the selected species, C.

jamaicense, C. javanicus, and C. polystachyos, were grown in 10 cm pots obtained from

Hui Ku Maoli Ola5 nursery, while 10 cm square potted C. laevigatus were supplied by

Dennis Kim’s6 nursery. Cyperus laevigatus plants which came from the nursery were

much younger than other species and had the lowest belowground and aboveground

biomass. Plants were established in the coir logs on November 20, 2007 by pulling coir

from the log to make a hole large enough to accommodate the belowground rooting

biomass and potting material. Plants were positioned in a randomized complete block

5 Hui Ku Maol Ola, Hawaiian plant specialists, 46-403 Ha'iku Rd in Kaneohe on Oahu. 6 Landscape architect and planning consultant, Waimānalo,Oahu.

31

Figure 2.3. The mesocosm experimental design.

32

design to minimize effects from position, distance, shading, or species interaction; this

design was replicated in each mesocosm. Two replicate plantings were planted at each

position in the coir logs. In this design, blocks were defined either by plant distance from

irrigation reservoir (row) or by each log itself (column).

Vegetation Sampling

Tissue collection

Plants obtained for the mesocosm experiment were sub-sampled for aboveground

tissue TN on a monthly basis beginning in December 2007 and continuing through June

2008. Each species from each log was subsampled during tissue collection (16 samples

per box, 48 samples per month). Representative subsamples were composited from

clippings of plants on each log. Initial clippings were taken one month after

acclimatization period (19 December 2007), and ammonium nitrate additions were added

after collection that same day. Clippings were as unobtrusive as possible, using whole

leaves (including stems for Cyperus polystachyos) and taking < 5% of total aboveground

biomass and obtained in the same manner each month. Clippings were brought back to

the laboratory and dried to a constant weight in a forced draft oven at 40°C for 48-72

hours and then ground into a homogeneous powder using a ball mill. Total N

concentration of the tissues were determined via combustion with a LECO CN2000

analyzer (LECO, Warriewood, Australia) at the University of Hawai‘i Mānoa Agriculture

Diagnostic Service Center (ADSC) Laboratory.

33

Biomass collection

During the final month of the experiment, a destructive harvest was used to

quantify aboveground plant biomass. Biomass sampling consisted of randomly selecting

a replicate of each species from every coir log. Only aboveground tissue material was

collected for this project due to inability to separate belowground root mass from coconut

coir netting. The aboveground biomass was collected and dried to a constant weight in a

forced draft oven at 40°C for 48-72 hours. Dry weight (DW) was recorded and compared

for differences within species and between nutrient levels. Biomass growth was

determined by surface area rather than vegetative clump diameter for consistency and

practical purposes. The natural clumping growth characteristic of C. jamaicense, C.

javanicus, and C. polystachyos typically encourages an increase in abundant canopy

growth and a wider distribution of individual plants. The surface area of harvest (m2) for

each plant was not assumed to be flat but was calculated using the top half of the

cylindrical coir logs which was exposed to the atmosphere (Figure 2.4). Weed and

senescent aboveground biomass was removed from growing area and from collected

samples.

34

Figure 2.4. Mesocosm coir log planting scheme with a side view of the exposed surface area.

Water Level

35

Aboveground Tissue TN Concentration and Uptake Rates

Average species accumulation rates (g TN m2 yr-1) were calculated using TN data

from the final month of the experiment. To determine uptake per year, the TN

concentration of each plant was multiplied by the aboveground biomass and N

accumulation rates were calculated based on the 7-month plant establishment period in

the mesocosms. Calculating accumulation per year was considered to be the most

practical and economic rate for use when determining large-scale remediation projects.

Statistical Analyses

Analysis of the data involved a general linear model (GLM) analysis of variance

(ANOVA). A randomized complete block design over the three mesocosms was used for

analysis with time, species, and N level as main effects. Blocks were also tested for

position of individuals in logs placed both horizontally as columns and by distance from

reservoir as rows. Blocks were tested individually using species averages over time.

Differences in main effects were tested using a GLM ANOVA and the Waller-Duncan K-

ratio t test to determine effects from exposure to elevated N levels. Species*Treatment

effects were analyzed using a post hoc test of means (lease significant difference [LSD]).

All statistical analysis were conducted with SAS version 9.1.3 (SAS Institute, Cary, N.C.

U.S.A.).

36

Results

Growth/survival:

During the eight-month trial, ending in July 2008, C. jamaicense, C. javanicus,

and C. polystachyos had 100% survival rate in coir logs across all three nutrient levels.

Cyperus laevigatus, on the other hand, had a significantly lower final survival rate (F =

19.11, p < 0.001) of 54% in June 2008.

Tissue TN Concentration

A repeated measures GLM ANOVA revealed that species accounted for the

greatest proportion of variance in the tissue TN concentration data (F = 193.03, p <

0.0001) (Table 2.3, Figure 2.5) with mean TN concentrations ranging from ~1% for C.

laevitigus to ~1.62% for C. jamaicense. According to the ANOVA, tissue TN

concentration changed significantly over time (F = 28.54, p < 0.0001). Accumulated

tissue TN varied markedly between species over time as the time*species interaction was

significant (F = 13.21, p < 0.0001). Although treatment was not shown to be significant

when combined over time, species*treatment effects had a p value of 0.08 (F = 1.91),

suggesting that there were marginal interaction effects (Figure 2.6). Further analysis

revealed that C. jamaicense showed significant differences across the N treatments (F =

6, p = 0.0041) (Figure 2.7).

Blocks (row and column) were tested via the combined ANOVA and column

blocking accounted for a significant portion of variance (F = 4.17, p = 0.0069). The

Waller-Duncan t-Test revealed that coir logs on the western edge of each mesososm had

a minimal significant TN difference of +0.06% over the subsequent logs mean when run

37

in the combined ANOVA. Although column blocking carried a low F-value, this

blocking variable was included for each month’s linear ANOVA and, when analyzed,

revealed no significance during any individual month. The mean aboveground tissue TN

concentration for the four species over the six month trial is presented in Table 2.4.

The effect of time was somewhat confounded due to complications during the

first few months of nutrient additions and the need to adjust hydroponic baseline

additions (see Methods). Although the baseline concentrations were altered during the

first months, the increased N additions were maintained at a consistent low, intermediate,

and high exposure across the mesocosms. For this reason, further results dealing with

time variance will focus on analysis from within each month. A GLM ANOVA was run

for each month using species, treatment, block (column), and the species*treatment

interaction. Treatment was significant during January and February 2008, and although

baseline nutrient levels were fluctuating during this period, a significant linear pattern

was observed across the N treatments (Figure 2.8).

Results from the beginning, middle, and end time periods of the experiment

revealed unique trends in tissue TN concentration by species which are discussed in

further detail below.

November 2007; Nursery plantings

Plant tissue TN concentrations from the original nursery stock were found to

exhibit significant differences among species (F = 189.45, p < 0.0001).

38

December 2007; Initial month sampling

During the one-month acclimation period, plants were exposed to the same level

of nutrients across treatments from the baseline fertilizer additions. Plant species

accounted for a significant proportion of variance (F = 32.73, p < 0.0001) in the initial

TN concentrations. Specifically, TN concentrations in C. polystachyos were significantly

lower than the other three species.

April 2008; Month 4 sampling

Beginning in April 2008, the additions of intermediate and high ammonium-N

were increased to a bi-weekly schedule. Species continued to account for a significant

proportion of variance in the tissue N data (F = 32.73, p < 0.0001). Specifically, Cladium

jamaicense, C. laevitagus, and C. polystachyos continued to show increased TN

concentrations, whereas TN in C. javanicus decreased. May 2008 showed the same

pattern of species tissue TN concentrations and significance with an even higher F-value

(F = 57.10, p < 0.0001).

June 2008; Month 6 sampling

The final month of sampling revealed a similar, but more exaggerated, pattern of

TN concentrations among species. Species again accounted for a significant proportion

of variance in tissue N (F = 32.73, p < 0.0001), however, the mean tissue TN

concentrations for all species dropped slightly compared to the previous months.

39

Table 2.3. Results from the combined GLM ANOVA testing mesocosm species tissue TN concentrations from December through May.

DF Sum of Squares Mean Squares F-statistic P-Value

Model 77 33.7480 0.4382 13.77 <0.0001

Error 193 6.1432 0.0318

Corrected Total 270 39.8912

Tissue TN Concentration as Dependant Variable

Block Row 3 0.1735 0.0578 1.82 0.1454

Block Column 3 0.3982 0.1327 4.17 0.0069

Species 3 18.4325 6.1442 193.03 <0.0001

Time 5 4.5417 0.9083 28.54 <0.0001

Treatment 2 0.0364 0.0182 0.57 0.5650

Treatment*Species 6 0.3642 0.0607 1.91 0.0815

Species*Time 15 6.3054 0.4204 13.21 <0.0001

Treatment*Time 10 1.0254 0.1025 3.22 0.0007

Treatment*Species*Time 30 1.7194 0.5731 1.80 0.0098

40

Figure 2.5. Total N concentrations (mean ± 1 standard error) among the four species (n = 72 for C. jamaicense and C. javanicus, n = 57 for C. laevigatus, n = 70 for C. polystachyos). Bars with different letters represent significant difference according to Waller-Duncan K-ratio t test (P<0.05).

0

0.5

1

1.5

2

C. jamaicense C. javanicus C. laevigatus C. polystachyos

Tota

l N (%

)

Species

c b a a

41

Figure 2.6. Total N concentrations (mean ± 1 standard error) among species*treatment effect. Bars with different letters represent significant differences according to the post hoc test of means (P<0.05).

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

C. jamaicense C. polystachyos C. javanicus C. laevigatus

Tota

l N (%

)

Species

Control

Intermediate

High

b a ab a ab a c c c d de e

42

Figure 2.7. A comparison of tissue N concentration (n = 72, mean ± 1 standard error) in plant aboveground biomass tissue for C. jamaicense across the N treatments (mesocosm). Bars with different letters represent significant difference according to Waller-Duncan K-ratio t test (P<0.05).

1.40

1.45

1.50

1.55

1.60

1.65

1.70

1.75

Control Intermediate High

Tota

l N (%

)

Mesocosm

a ab bc

43

Table 2.4. A comparison of mean tissue total N concentrations (percent ± standard deviation) in aboveground tissue for the four species over all sampling dates from all three N treatments. [(***) n = 1, (**) n = 2, (*) n = 3].

Plant Species and Treatment Growth

C. jamaicense C. javanicus C. laevigatus C. polystachyos TN TN TN TN

Initial Control 1.05 ± 0.06 1.14 ± 0.09 0.85 ± 0.24 1.14 ± 0.09 Intermediate 1.04 ± 0.09 1.17 ± 0.13 0.64 ± 0.18 1.17 ± 0.13 High 1.10 ± 0.06 1.08 ± 0.19* 0.65 ± 0.06 1.08 ± 0.19* Month 1 Control 1.17 ± 0.17 1.42 ± 0.08* 1.17 ± 0.08 1.42 ± 0.08* Intermediate 1.22 ± 0.09 1.31 ± 0.08 0.55 ± 0.29 1.31 ± 0.08 High 1.15 ± 0.10 1.50 ± 0.15 0.70 ± 0.26 1.50 ± 0.15 Month 2 Control 0.79 ± 0.06 1.15 ± 0.08 0.67 ± 0.24 1.15 ± 0.08 Intermediate 1.22 ± 0.09 1.32 ± 0.10 0.55 ± 0.29 1.32 ± 0.10 High 1.10 ± 0.13 1.41 ± 0.22 0.92 ± 0.65 1.41 ± 0.22 Month 4 Control 0.87 ± 0.10 1.33*** 1.48 ± 0.30 1.33*** Intermediate 0.90 ± 0.05 1.53 ± 0.12 1.20 ± 0.51 1.53 ± 0.12 High 0.83 ± 0.08 1.38 ± 0.34* 1.31 ± 0.13 1.38 ± 0.34* Month 5 Control 1.00 ± 0.05 1.57 ± 0.01** 1.23 ± 0.44 1.57 ± 0.01** Intermediate 0.92 ± 0.09 1.48 ± 0.04 1.55 ± 0.27 1.48 ± 0.04 High 0.85 ± 0.10 1.36 ± 0.24** 1.35 ± 0.11** 1.36 ± 0.24** Month 6 Control 0.96 ± 0.06 1.50 ± 0.08* 1.05 ± 0.18 1.50 ± 0.08* Intermediate 0.87 ± 0.09 1.36 ± 0.13 1.21 ± 0.19 1.36 ± 0.13 High 1.05 ± 0.16 1.42 ± 0.03 1.31 ± 0.26 1.42 ± 0.03

44

Figure 2.8. Total N concentrations (mean ± 1 standard error) during February 2008. (a.) Species accounted for a significant proportion of variance (F = 23.79, p = < 0.001; n = 12, n = 10 for C. laevigatus), (b.) treatment accounted for a lesser but nonetheless significant proportion of variance (F = 5.4, p = < 0.001; n = 16, n = 15 for high). Bars with different letters represent significant difference according to Waller-Duncan K-ratio t test (P<0.05).

0.000.200.400.600.801.001.201.401.601.802.00


Species

0.000.200.400.600.801.001.201.401.601.802.00


Tot

al N

(%)

a.

b.

a b b

d cb a

45

Figure 2.9. Total TN concentrations (mean ± 1 standard error) of the four plant species over time. (a) Nursery plantings (n = 3) November 2007. (b) Mesocosm December 2008 (n = 12). (c) Mesocosm April 2008 (n = 12, n = 8 for C. laevigatus). (d) Mesocosm June 2008 (n = 12, n = 10 for C. laevigatus). Bars with different letters represent significant difference according to Waller-Duncan K-ratio t test (P<0.05).

46

0

0.5

1

1.5

2

0

0.5

1

1.5

2

0

0.5

1

1.5

2

0.0

0.5

1.0

1.5

2.0


Species

Tot

al N

(%)

b c d

d b a c

a

ba b c

b b a b

a.

b.

c.

d.

47

Aboveground Biomass

After 7 months of growth in the mesocosms, aboveground biomass DW had a

minimum value of ~ 0.86 g m-2 for C. laevigatus and a maximum value of ~ 5,494 g m-2

C. jamaicense. The ANOVA indicated that species accounted for the highest proportion

of the variance in the biomass data (F = 87.05, p < 0.0001) (Table 2.5) with mean species

biomass ranging from 52 g m-2 for C. laevigatus to ~ 3,452 g m-2 for C. jamaicense. The

ANOVA revealed that a significant proportion of variance was attributed to the

species*treatment interaction (F = 3.25, p = 0.014) (Figure 2.10). Further ANOVA

analysis within species, which included blocking by column, revealed that treatment was

nearly significant for C. jamaicense with a p-value of 0.0574, with a significant increase

in biomass with exposure to the high N level. Although C. polystachyos did not show

significant differences across the N treatments, mean biomass followed a decreasing

trend with values of ~603, ~408, and, ~ 200 g m-2 in the control, intermediate, and high N

concentration mesocosms, respectively.

48

Table 2.5. Results from the combined GLM ANOVA testing mesocosm species aboveground biomass.


Model 14 904807323.78 6462908.84 20.49 <0.0001

Error 30 9461343.67 315378.12


Biomass as Dependant Variable

Block (Column) 3 648558.88 216186.29 0.69 0.5679

Species 3 82364895.41 27454965.14 87.05 <0.0001

Treatment 2 10226698.07 511349.03 1.62 0.2145

Species*Treatment 6 6143013.54 1023835.59 3.25 0.0140

49

Figure 2.10. Mean aboveground biomass (mean ± 1 standard error) of the four plant species across the treatments (mesocosms) (n = 4). Bars with different letters represent significant differences according to the post hoc test of means (P<0.05).

0

1000

2000

3000

4000

5000

6000


g m

-2

Species

Control

Intermediate

High

bc d c cd a a c b a a a a

50

N Accumulation Rates

The mean calculated aboveground N accumulation rates (Table 2.6) ranged across

species from ~ 1.4 g TN m2 yr-1 for C. laevigatus to ~ 96.2 g TN m2 yr-1 for C.

jamaicense. The ANOVA showed a significant proportion of the variance was accounted

for by species (F = 111.01, p < 0.0001) and treatment (F = 4.77, p = 0.02) (Table 2.7).

The ANOVA also indicated that a significant proportion of variance was attributed to the

species*treatment interaction (F = 4.05, p = 0.005) (Figure 2.11).

51

Table 2.6. Total nitrogen accumulation rates (mean ± standard deviation) in June 2008 for different species and treatment mesocosms. The different letters represent the significant differences according to Waller-Duncan K-ratio t test (P<0.05) in the same species (n = 4, n = 3 for C. laevigatus, n = 2 for C. laevigatus in High).

Mesocosm Treatment (g TN m2 yr-1)

Species Control Intermediate High

C. jamaicense 81.28 ± 5.48a 79.02 ± 17.47a 128.26 ± 31.82b

C. javanicus 38.07 ± 4.44 28.65 ± 11.67 37.84 ± 17.61

C. laevigatus 0.1 ± 0.05a 1.46 ± 1.04ab 3.25 ± 3.96b

C. polystachyos 11.35 ± 8.81 8.76 ± 7.44 4.99 ± 5.65

52

Table 2.7. Results from the combined GLM ANOVA testing mesocosm species TN accumulation rates.


Model 14 69132.27149 4938.0193 26.87 <0.0001

Error 29 5329.1474 183.7637


Biomass as Dependant Variable

Block (Column) 3 625.0046 208.3349 1.13 0.3518

Species 3 61198.5806 20399.5269 111.01 <0.0001

Treatment 2 1751.3058 875.6529 4.77 0.0162

Species*Treatment 6 4468.1986 744.6998 4.05 0.0045

53

Figure 2.11. Mean aboveground TN accumulation (mean ± 1 standard error) of the four plant species across the treatments (mesocosms) (n = 4, n = 3 for C. laevigatus). Bars with different letters represent significant differences according to the post hoc test of means (P<0.05).

0

20

40

60

80

100

120

140

160

180


g T

N m

2y-1

Species

Control

Intermediate

High

b b b a a a a a a c c d

54

Discussion and Conclusions

Survival and Growth

At the conclusion of the experiment, C. jamaicense, C. javanicus, and C. polystachyos

had 100% survival rate in each of the three mesocosms, while C. laevigatus had considerably

lower survival rate. After one year in a field study by Brimacombe (2002), C. javanicus, C.

polystachyos, and C. laevigatus had survival rates of 96.5%, 59.3% and 76%, respectively.

Brimacombe (2002) stated that the physical appearance of C. laevigatus was quite poor and

showed that varying planting density or competition for C. laevigatus did not significantly affect

percent survival or health. Across the treatments, the mean biomass of Cyperus laevigatus

ranged from~3.72 g m-2 in the control treatment to ~90.64 g m-2 in the high treatment, however,

these differences were not significant. In Van Dyke’s (2001) study, which investigated the

potential use of C. laevigatus for wastewater treatment, C. laevigatus plants exposed to higher

nutrient levels were substantially taller and darker green in color than those in lower nutrient

levels. The difference in this study may have been due to the coconut coir logs. This indicated

that C. laevigatus was unsuccessful at establishing in this type of media and therefore did not

support Hypothesis 2.1. The November planting may have been another negative factor in C.

laevigatus performance as it is listed as a perennial in Erickson and Pottock’s (2006) Field

Guide. In addition, Van Dyke (2001) observed a cyclic dieback for C. laevigatus beginning in

October. Cyperus laevigatus seemed to be at a disadvantage from the start due to the young age

of the available nursery plant material which lacked substantial above and belowground biomass.

Brimacombe’s (2002) study started with “weak and spindly” C. laevigatus nursery plants and

achieved a 76% survival rate after a year; however these were out-planted in a field trial which

55

consisted of different wetland habitat soils and survivors were described as having quite poor

physical appearance. The successful establishment and survival of native riparian species C.

jamaicense, C. javanicus, and C. polystachyos in coconut coir log media supported Hypothesis

2-1.


Hypothesis 2.2a was supported throughout the study as species continually accounted for

the greatest proportion of variance in tissue TN concentration. While differences in TN

concentration among species were apparent from nursery samples and continued throughout the

study, the pattern of accumulation changed over time as each species developed. This variation

among species and their tissue N concentration is supported by previous studies that investigated

the nutrient concentration among wetland plants in constructed wetland environments

(McJannet, Keddy et al. 1995; Greenway 1997); and by Boyd (1970; 1978) who observed

significant interspecific variation of aquatic plants in his field study. Differences in the nursery

TN concentrations likely represented the age difference among species and the highly variable

growing situation of different nurseries and their likely different nutrient addition rates.

Although data collection ended in June, a slight decline in combined species TN concentration

was observed from May to June. A longer study with regular temporal sampling would be

necessary to identify thresholds and long-term accumulation patterns of individual species.

The blocking effect from the combined ANOVA revealed that coir logs in position four,

located on the western edge of each mesososm, had a lesser but significant effect on TN

concentration. An explanation for this result includes the fact that the project site was located in

a valley where the early hours of sunlight were blocked by cliffs to the east. An edge effect was

56

also found in Tanner’s (1996) constructed wetland study which he equated to the exposure of

lateral as well as downward solar radiation. There may have also been a flow effect from the

reservoir t-pipe fittings which diverted more reservoir outflow to the western side of mesocosms.

During the first two months, treatment was a significant factor in the ANOVA which

might have been the result of higher N uptake into tissue by species at an early age. This was

supported by claims that during initial establishment (when nutrient storage compartments were

still expanding), net nutrient storage will be significant in removing N from constructed wetlands

(Tanner 1996). Shaver and Milillo (1984) have demonstrated that the efficiency of N uptake for

wetland plant species tends to decrease over time as available nutrient inputs increase. Tanner

(1996) suggested that long-term studies of tissue nutrient levels will likely reflect key ecological

traits of species, such as nutrient use efficiency, with either increasing growth to maximize

production or tending towards a more conservative strategy of nutrient accumulation. Overall,

the N addition treatment was not significant and therefore this did not support hypothesis 2-2b.

However, C. jamaicense showed significantly higher tissue TN concentrations in the highest

nutrient addition treatment. Cladium jamaicense Crantz, also native to the Florida Everglades, is

a slow-growing rhizomatous, perennial sedge commonly found in nutrient-poor freshwater

marshes. Miao (1997) and Lissner (2003) have studied C. jamaicense Crantz in Florida and

speculate that due to this species adaptability to low resource environments, it grows slowly, has

low population growth, long life cycles, low reproductive yield, and responds to resource

changes slowly; resulting in high nutrient storage to maximize benefits during times of stress.

Inter-species differences became even more significant in the latter part of the experiment

(Spring 2008). April results showed Cladium jamaicense, C. laevitagus, and C. polystachyos

with increased TN concentrations, whereas TN concentrations in C. javanicus had decreased.

57

Between March 2008 and April 2008, C. javanicus had begun to develop flowers and fruits.

Cyperus javanicus¸ in general, produces many inflorescences bearing multiple branches of

flattened, lanceolate spikelets which protrude off of a long and highly fiberous culm (Erickson

and Pottock 2006). At this time, C. javanicus was transitioning from developing rapid growing

juvenile leaf tissue, which utilizes N for photosynthesis, to producing a more carbon-rich and

carbohydrate intensive material (Taiz and Zeiger 2002).

The tissue TN concentrations changed over time but differences remained significant

among species. Both Güsewell (2002) and Greenway (1997) found that tissue N concentrations

varied more among species than among sites, and Chapin (1980) concluded that leaf nutrient

content can vary between species seasonally. There was a rapid increase in biomass during the

last month and mesocosm water sampling revealed an increase in the rate of N uptake. It was

possible that the N additions did not keep up with the rapid development of new growth and may

have influenced the overall drop in tissue TN concentration during this time.

Biomass Growth

Plant biomass varied widely across the four species, supporting hypothesis 2.2a. These

aboveground biomass patterns may be explained by their physiological, ecological and

morphological differences, such as plant size and reproductive traits. Although treatment was

not shown to be a significant factor in the GLM ANOVA (F = 1.62, p < 0.2145), the highest N

treatment mesocosm resulted in slightly higher mean biomass values when compared with the

control and intermediate treatment mesocosm (Figure 2.12).

Cladium jamaicense produced the largest amount of biomass of the four species and

showed a significant increase in biomass with exposure to elevated N levels. Miao and Sklar

58

(1997) also showed C. jamaicense biomass to increase along a nutrient gradient of impacted and

referenced sites of the Florida Everglades. As mentioned for tissue TN concentration, this

species is adapted to low nutrient environments and to areas of frequent disturbance thus, the

response of increased growth during exposure to increased N levels may be an adaptation to

maximize benefits during times of stress (Chapin 1980; Miao and Sklar 1997). Cladium

jamaicense never produced flowers during the length of the experiment. However, numerous

new shoots from vegetative reproduction were observed to push easily through the coir log.

During the last few months, the erect caulines of C. jamaicense began to form a canopy.

Cyperus javanicus had the next highest biomass and produced new vegetative leaf

sheaths directly after planting. During the first few months of the experiment when baseline

nutrient additions were being adjusted for the mesocosms, C. javanicus responded quickly to a

decrease in nutrient level by ceasing growth and by senescence of older tissue material. After

nutrients were raised, this species quickly rejuvenated and persisted with competitive growth. At

the time of the biomass harvest, C. javanicus had produced multiple reproductive stems of which

a majority was in seed ripening, seed setting, and in the senescent stage of reproduction

(Brimacombe 2002). The proportion of reproductive material for C. javanicus likely influenced

final biomass results.

Interestingly, C. polystachyos had an inverse correlation with biomass growth and N

nutrient additions, which McJannet (1995) found to be a trend among 41 wetland plants. This

downward trend in biomass growth may reflect the nutrient tolerance level and/or growth habits

(i.e. reproductive characteristics) of this species. C. polystachyos was successful overall in

biomass growth and was able to compete in close quarters with C. jamaicense and C. javanicus

which, on average, produced ~ 9X more biomass. Cyperus polystachyos also developed a

59

distinct morphological feature throughout the study--the growth of reproductive stems and

flowers verses basal leaves. In the majority of individuals, reproductive material seemed to

outweigh basal leaf growth. Brimacombe (2002) reported 99% of out-planted C. polystachyos

individuals produced reproductive stems after one month. A more complete understanding of the

uptake potential for C. polystachyos would benefit from further study of its different

physiological components, for example, leaf verses stem nutrient concentrations. There was a

snail infestation in May 2008 which seemed to mainly affect C. polystachyos. This was quickly

brought under control through intensive hand removal. Other studies mentioned that Cyperus

polystachyos can have moderate pest issues, mainly aphids; however these did not appear to

affect the health of the plant (FLC 2001).

Cyperus laevigatus had the least biomass growth of all the species. This was not

surprising nor was it an indication of the lack of success for this species. This species is

generally much smaller in stature than the other species and tends to grow on the edge of water

bodies (Erickson and Pottock 2006). Position in mesocosm was not determined significant and,

during the latter part of the experiment, the most prolific culms of C. laevigatus were produced

by creeping rhizomes found in the interior of the mesocosms which were found through the thick

canopy of C. jamaicense and C. javanicus (Figure 2.13). Historically, C. laevigatus was used in

Hawai‘i for weaving mats and was recorded to reach lengths of 1-2 m.; today, however, most

culms in Hawai‘i fall within the range of 10-45 cm. (Van-Dyke 2001). Although our study did

not record length, observation and photographs show species within this range. Cyperus

laevigatus biomass growth generally increased with N additions but the differences across the

treatments were not significant.

60

Figure 2.12. Total aboveground biomass (mean ± 1 standard error) across the N addition treatments (n = 15).

0

500

1000

1500

2000

2500


g m

2

Mesocosm

61

Figure 2.13. This photo illustrates the creeping rhizomatous growth of Cyperus laevigatus observed in some of the mesocoms.

62

Interestingly, this species has been a preferred candidate for wastewater treatment in

Hawai‘i (FLC 2001; Van-Dyke 2001). Our results, in agreement with Brimacombe’s

(2002) findings, showed that C. laevigatus requires high maintenance, dense planting,

and higher nutrients to attain successful establishment.


Tissue N accumulation rates varied widely among the four species, supporting

hypothesis 2.2a, but were not shown to vary significantly across N treatments. Nitrogen

accumulation for C. jamiacense was within a similar range of others studies (Miao and

Sklar 1997; Lissner, Mendelssohn et al. 2003), as well as, for Cyperus species (McJannet,

Keddy et al. 1995; Tanner 1996; Greenway 1997; Xu, Yan et al. 2006). Mean TN

accumulation rates for each species largely reflected the pattern shown with biomass

growth. Accumulation rates were calculated based on this seven-month trial in order to

best represent nutrient removal for restoration projects utilizing young nursery plants.

There was significant variation across species and maximum accumulation rates were

recorded in the larger species. Cladium jamaicense and Cyperus laevigatus showed the

most promise for N accumulation with increasing biomass growth, however, survival,

biomass growth, and accumulation rates need to be considered when making

management decisions for stream restoration. Cyperus laevigatus has shown promise for

its ability to treat wastewater with high removal rates (FLC 2001; Van-Dyke 2001) and

our study suggests that this species has potential to remove N at a competitive rate when

sufficient biomass is produced.

63

Tissue N accumulation rates were achieved under conditions of abundant N

supply and likely reflected key ecological traits of the species (Tanner 1996). Chapin

(1980) theorized that the differences in biomass and nutrient assimilation in plant tissue

are associated with different functions of plant growth and with plant responses to

contrasting resource habitats; plants seem to adjust resource allocation in response to

their immediate environment. Chapin (1980) also concluded that as soil nutrient levels

increase there is a corresponding increase in growth rate of species from fertile sites,

whereas species from infertile sites maintain lower growth rates with a combined increase

in tissue nutrient concentration. Multiple studies have supported this theory, and further

suggest that patterns of assimilation and storage may not be a universal feature of plants

from certain sites and that the developmental state of propagules may be more important

than biomass of the propagule (McJannet, Keddy et al. 1995; Tanner 1996; N. J. Willby

2001). McJannet’s (1995) study tested Chapin’s theory by using tissue nutrient content

of 41 wetland plants to predict the responses of groups of species to perturbations such as

fertilization and found that, in respect to N content, there was no significant difference

between infertile and fertile sites.

Cladium jamiacense was not reproductive during this trial, rather it concentrated

its growth on new shoots and developing leaf biomass. This species is adapted to low

nutrient environments and its overall success in biomass growth and TN accumulation

may relate to indirect correlations with morphological traits, such as the ratio of light

harvesting to supportive tissue, that confer a competitive advantage in particular

environments (Chapin, 1980).

64

This mesocosm experiment provided an ideal environment for a study using a coir

log medium and desired species with potential to accumulate excess N found in the

polluted surface waters of Waimānalo Stream. This experiment showed that TN was

assimilated into the tissues of the selected species at significantly different concentrations

throughout the experiment. Although the tissue TN concentrations were greatest with C.

jamaicense and C. laevatigus, the effect of biomass growth had an overwhelming effect

on accumulation potential and resulted in accumulation rates to be the greatest for C.

jamaicense and lowest for C. laevatigus. Selection of species for restoration in the field

should consider species that will produce abundant biomass and have the ability to store

substantial TN in its tissue.

65

Chapter 3: Field Installation of Pre-Planted Coir Logs in

Waimānalo Stream

Introduction

Waimānalo Stream, located in eastern Oahu, has remained on Hawai‘i’s 303(d)

listing of impaired waterways for over the past 10 years (HIDOH 1998; HIDOH 2006).

This listing is in large part due to excess nitrogen (N) loading from both point and non-

point sources within the Waimānalo watershed (Harrigan and Burr 2001; USEPA 2001;

Laws and Ferentinos 2003). In Hawai‘i and elsewhere, changes in land-use patterns such

as agricultural intensification, urban expansion, and stream hardening for flood control

have increased sediment and nutrient loading in streams and coastal regions (Peierls,

Caraco et al. 1991; Vitousek, Aber et al. 1997; Laws and Roth 2004; Bruland 2008).

Although point- and non-point sources account for substantial amounts of sediment and

nutrient delivery to Waimānalo’s aquatic ecosystems, an important component of this

problem is associated with the degradation and destruction of riparian buffer zones which

would normally help to minimize impacts of land runoff (Laws and Ferentinos 2003).

In an effort to improve the degraded condition of Waimānalo Stream, a Total

Maximum Daily Load (TMDL) assessment of pollutants was conducted to identify areas

where sediments and nutrients exceed the stream’s capacity for assimilation and

recycling (Harrigan and Burr 2001). Following this assessment, a report for an effective

implementation program concluded that the highest priority projects would be ones that:

1) directly benefit the immediate proximity of the stream (i.e. instream, riparian, or

adjacent to stream) and/or, 2) reduce pollutants in the identified segments of the

watershed where the TMDL’s are currently not being met (USEPA 2001).

66

The field installation phase focused on sections along Waimānalo Stream’s two

main tributaries: Kahawai Stream to the southeast and Waimānalo Stream to the

northwest, which merge roughly 0.5 km below the Kalaniana’ole Highway (Harrigan and

Burr 2001; KBAC 2002; Laws and Ferentinos 2003) (Figure 1.1). Unless otherwise

noted, the term “Waimānalo Stream” will include both Waimānalo and Kahawai

tributaries. The stream channel of this reach is managed as a floodway to convey water

off of land and to the sea. Stream banks are regularly ‘maintained’ by being sprayed with

herbicide down to the water edge to eliminate vegetation (USEPA 1998). This repeated

removal of vegetation is necessary only because of the current riparian vegetation

consists mostly of non-native species such as Pennisetum purpureum (cane grass),

Panicum maximum (guinea grass), and Coix lachryma-jobi (Job’s tears). The clearing of

riparian trees has reduced the shading and has lead to the proliferation of herbaceous

vegetation within the channel (Laws and Ferentinos 2003). These alien species alter the

function of the stream by creating a thick matt of biomass that restricts stream flow and

causes flooding during heavy rains as well as lowering vegetative diversity (Laws and

Ferentinos 2003). Selecting native vegetation for establishment on the riparian banks of

Waimānalo stream will support both species richness and composition. The number,

relative abundance, identity, and interaction of species all affect ecosystem processes

(Chapin, Matson et al. 2002). Riparian plantings often act as a sink for nutrients from

runoff waters because they can remove nutrients in both surface and shallow groundwater

(Pinay, Fabre et al. 1992).

The streams in Waimānalo watershed, as well as streams throughout Hawai‘i, are

prone to episodic flash floods and prolonged periods of low flows (Tomlinson and

67

DeCarlo 2003). The combined effects of riparian tree removal, repeated herbicide

application, and flash floods have decreased the stream’s physical structure which has led

to substantial bank erosion and increased sediment loss to surface waters. This presents a

challenge for restoration projects attempting to establish vegetation in affected and

exposed riparian substrate.

An EPA Bioassessment Report for Hawai‘i rated the health of riparian areas

based upon the width of the vegetated zone and understory coverage, stating that

vegetative protection is most critical within five meters of the water’s edge (Kido 2002).

Ecologically-intact riparian areas naturally prevent erosion, retain and recycle nutrients,

modify local microclimates, and sustain food webs that help support a diverse

assemblage of fish and wildlife (NRC 2002). Restoring riparian vegetation along

Waimānalo stream is a viable, cost-effective, and ‘natural’ surface water treatment

technology known as phytoremediation. Phytoremediation can be defined as the clean-up

of pollutants primarily mediated by photosynthetic plants (Horne 2000). Studies which

quantify the efficiency of wetland plants for phytoremediation purposes do so by

analyzing the nutrient concentrations in plant biomass. Many of these studies have

shown that nutrient uptake rate by species can vary widely even when experiencing the

same nutrient availability (McJannet, Keddy et al. 1995; Tanner 1996; Tanner 2001;

Greenway 2005; Xu, Yan et al. 2006). Different nutrient accumulation rates may be due

to inherent physiological and key ecological traits (Chapin, Bloom et al. 1987). In

utilizing the concepts of phytoremediation along the riparian banks of Waimānalo

Stream, the selection of species, design, installation method, and mitigation success

become important factors. Quantifying nutrient accumulation rates by species can

68

indicate how a species or group of species will perform in varying nutrient levels (Miao

and Sklar 1997; N. J. Willby 2001), and will provide further guidance for the

management of stream remediation efforts.

Selection of native species that will survive and restore valuable functions

requires an ecosystem perspective that encompasses the concepts that define the current

state of Waimānalo stream (Ehrenfeld and Toth 1997). Plants were selected based on

results from the previous chapter, Planted Coir Log Nutrient Addition Experiment. The

field design implemented stream bioengineering techniques with the use of coconut coir

logs. Pre-planted coir logs have been successfully used in the continental U.S. for toe

stabilization along stream banks to prevent erosion and establish vegetation (Allen and

Leech 1997), however this technique has neither been demonstrated with Hawaiian plants

nor under the highly variable flow rates found in Hawai‘i. Installation of pre-planted coir

logs along stream banks will take advantage of log stability and bank protection to

encourage roots to grow into the bank as the coir material degrades while hopefully being

able to withstand Hawai‘i’s intense flash floods.

The main purpose of this chapter is to test the utilization of pre-planted coir logs

in the toe zone and along the banks of Waimānalo stream. The toe zone is the portion of

the stream bank between the bed and average normal stage flow and is a zone of high

stress often undercut by currents and resulting in bank failure unless preventative or

corrective measures are taken (Allen and Leech 1997).

Objectives and Hypothesis

The specific objectives and hypotheses of this chapter are outlined below.

69

Objective 3-1: Monitor nitrate, ammonium, and total dissolved N from Waimānalo and

Kahawai streams.

Objective 3-2: Install and monitor coir logs planted with native species along 92 meters

(m) of each stream.

Hypothesis 3-1: Plants in coir logs of Kahawai stream will have higher tissue N

concentration and aboveground biomass than plants in coir logs of Waimānalo stream as

Kahawai stream has consistently higher surface water N levels than Waimānalo stream.

Materials and Methods

Species Selection

The previous chapter evaluated candidate species for the field installation phase

of this project. Based on these results, the following three species were selected for field

installation on coir logs due to their survival rate, aboveground biomass growth, and

tissue TN accumulation: Cladium jamaicense, Cyperus javanicus, and Cyperus

polystachyos.

Pre-Planted Coir Logs

Sixty coconut coir logs, made from 100% coconut coir and measuring 3.05 m in

length with a diameter of 0.20 m, were planted in February 2008 at the Hui Ku Maoli Ola

Nursery located in Kaneohe, (21°24'42.58"N, 157°49'4.61"W). Each log was planted

with one of the three species with an individual every 0.15 m, totaling 18 plants per log.

Logs were cared for at the nursery through June 2008 with overhead irrigation and

70

occasional fertilization. Cyperus polystachyos was replanted during this time at the

nursery due to a snail infestation which decreased aboveground biomass.

Experimental Site and Procedures

In June 2008, coir logs were installed in both Waimānalo Stream and Kahawai

Stream sites. Thirty logs per stream covered 92 m of each stream. Logs were installed

along the toe of the stream ensuring that the bottoms of the logs were either partly

submerged or were at least touching the water. Logs were secured to the toe using 0.61 x

0.05 m wooden stakes, typically using 6 – 8 stakes per log. Logs were placed in a

randomized design along each bank, where blocks were based upon bank side to account

for any differences in slope, shading, water depth, or weeds. Erosion matting was laid

out along the bank and individual native plants were planted in the riparian area between

the installed coir logs and before the bank’s rising slope to impede competition from

weeds during the establishment phase.

Challenges Encountered

A major set-back for the field experiment arose when personnel from the

Department of Land and Natural Resources (DLNR) performed their regular herbicide

application and sprayed through the designated restoration sites and installed coir logs.

Waimānalo Stream was sprayed in early June and Kahawai Stream was sprayed in late

August. Due to the lethal effects of the herbicides on the native plants growing in the

coir logs at both experimental sites, the decision was made to attempt to utilize existing

log material for replanting. However, the existing coir logs were showing signs of

71

degradation and instability from water and solar exposure. Thus, new coir logs were

purchased for planting and reinstallation in both streams on November 28, 2008. Due to

budgetary limitations, 12 new coir logs were used to replace 12 of the existing logs for a

scaled down version of the original experimental design (Figures 3.1, 3.2). New logs,

which were 3.05 m in length and 0.25 m in diameter, were planted with the same method

as the original logs and installed along each stream section. Individual plants were also

planted in degraded coir logs and in the riparian zone between logs and bank slope;

however these were not analyzed for biomass or tissue concentration.

New logs and plants were installed in stream sections on November 28th, 2008.

After this installation, a significant rainfall event occurred on December 11th, 2008.

Rainfall data were acquired from the Waimānalo sampling station (National Weather

Service, station HI-13) (Figure 3.3). On this day a flash flood event occurred on which

the streams were filled to capacity and restorated stream reaches were inundated by

several meters of water. This flood event led to the loss of three logs along one of the

banks of Waimānalo stream, and although Kahawai stream did not lose any logs, one log

was covered with heavy sediment which suffocated the C. javanicus plants (Figure 3.4).

72

Figure 3.1. The Waimānalo Stream reach with coir log layout and experimental log placement.

73

Figure 3.2. The Kahawai Stream reach with coir log layout and experimental log placement.

74

Figure 3.3. Rainfall data during the December 2008 storm event. Data obtained from the National Weather Service (NWS) Waimānalo station (HI13).

75

Figure 3.4. The experimental coir log layout after the December 28, 2008 flood event.

76

Stream Sample Collection and Laboratory Analysis

Water Collection

Surface water was sampled from both upstream and downstream areas of the two

stream sections. Samples were collected in 50 mL plastic centrifuge tubes and

immediately put in a cooler with ice. Stream physical and chemical water properties,

such as pH and temperature were monitored using a handheld YSI Model 556 Multi

probe system (YSI Instruments, Yellow Springs, OH). Water samples were analyzed for

total nitrogen (TN), total dissolved nitrogen (TDN), nitrate + nitrite nitrogen (NO3--N +

NO2--N), and ammonium nitrogen (NH4-N). Quarterly water samples were sent to the

Marine Science Analytical Lab (MSAL) at UH Hilo for TDN analysis determined

through the use the ASTM Method D5176 (ASTM 1995). Bi-monthly samples were

analyzed at the University of Hawai‘i Mānoa Agriculture Diagnostic Service Center

(ADSC) Laboratory for TN analysis using the micro-Kjeldahl method (CTAHR 2000).

Vegetation Sampling

Biomass and Tissue Collection

Due to the set-back with the herbicide application, plants in the experimental coir

logs grew for three months before a destructive harvest was used to measure tissue TN

concentration, aboveground biomass, and determine TN accumulation. Biomass

sampling consisted of randomly selecting 8 replicates from each remaining experimental

coir log. The aboveground biomass was collected and dried to a constant weight in a

forced draft oven at 40°C for 48-72 hours. After biomass weights were recorded, dried

77

material was subsampled and ground into a homogeneous powder using a ball mill. Total

N values of the plant tissues were determined via combustion with a LECO CN2000

analyzer (LECO, Warriewood, Australia) at the ADSC.

Tissue TN Concentration and Accumulation Rates

Aboveground tissue TN accumulation rates (g TN m2 yr-1) for each species were

calculated using TN data from the final month of the experiment. The TN concentration

was multiplied by the aboveground biomass (g m-2), and accumulation rates were

calculated based on the three-month plant establishment period in the streams.

Statistical Analyses

Tissue TN concentration and biomass were compared among species and between

stream locations. The surface area of harvest (m2) for each plant was not assumed to be

flat but was calculated using the top half of the cylindrical coir log as in Chapter 2

(Figure 2.4). Analysis of the data involved a general linear model (GLM) analysis of

variance (ANOVA) using the main effects of species, stream, and their interaction

(species*stream). A randomized complete block design over two streams was used for

analysis, however, the loss of logs along one of the banks of Waimānalo Stream and the

loss of one species in Kahawai Stream compromised the blocking effect. Differences in

main effects were tested using a GLM ANOVA and the Waller-Duncan K-ratio t test to

determine effects from exposure to elevated N levels. Species*treatment effects were

tested using a post hoc test of means (LSD). All statistical analysis were conducted with

SAS version 9.1.3 (SAS Institute, Cary, N.C. U.S.A.).

78

Results

Water Sampling

The physiochemical characteristics of the surface water in both streams were

monitored throughout the project beginning in September 2007 and continuing through

January 2009. The mean physiological characteristics ensured no major differences

between upstream and downstream, but certain showed trends for the differences between

each stream (Table 3.1). Waimānalo Stream consistently had lower water temperatures

and had higher pH and DO than Kahawai Stream. Surface water N levels were

consistently greater in Kahawai Stream than in Waimānalo Stream. Nitrate- + Nitrite-

Nitrogen accounted for most of the TDN at all times, with a median ratio (Nitrate +

Nitrite / TDN) of 100% for Kahawai Stream and 74% for Waimānalo Stream. The mean

N data of the samples collected were compared with the State’s inland water quality

standards as defined by Hawai‘i’s Administrative Rules (HIDOH 2004)(Table 3.2). For

both streams, surface water N data exceeded that of the State’s water quality standards

for TN (0.25 mg L-1 for the wet season and 0.18 mg L-1 for the dry season) and for

Nitrate+Nitrite-Nitrogen (0.07 mg L-1 for the wet season and 0.03 mg L-1 for the dry

season) (Figure 3.5).

79

Table 3.1. Mean stream physiochemical characteristics of Kahawai and Waimānalo streams at locations upstream and downstream of remediation site from September 2007 through February 2009 (n = 15).

Stream Kahawai Waimānalo Parameter Upstream Downstream Upstream Downstream Dissolved Oxygen (%) 25.51 36.62 46.43 33.53 Temperature (oC) 28.22 28.31 27.57 27.75 pH 7.67 7.73 8.60 8.53 Conductivity (us cm-1) 0.46 0.42 0.41 0.40 Total Dissolved Solids (g L-1) 0.30 0.27 0.27 0.26 Salinity (‰) 0.22 0.20 0.20 0.19

80

Table 3.2. Mean concentration (mg L-1) of Total Nitrogen (TN) and Nitrate- + Nitrite-Nitrogen collected in Kahawai and Waimānalo Streams from September 2007 through February 2009, and compared with the State water quality standards* during the wet and dry season** and during storm event***.

Stream Nitrogen (mg L-1)

Standard* Waimānalo Kahawai

Wet Dry Wet Dry Storm Wet Dry Storm

TN 0.25 0.18 1.18 0.30 N/A 5.50 2.49 N/A

NO3-+NO2

+ 0.07 0.03 1.06 0.22 2.94 5.47 4.09 5.10

* DOH (2004) Chapter 11-54; Inland water criteria. Geometric mean not to exceed the given value (HIDOH 2004) ** Wet Season = November 1 - April 30 (n = 10)

Dry Season = May 1 - October 31 (n = 4) *** Storm Event on December 11, 2008

81

Figure 3.5. Mean values of Total Nitrogen (TN), Total Dissolved Nitrogen (TDN), and Nitrate+Nitrite-Nitrogen (NO3

—N+NO2--N) from September 2007 through February 2009. Figure A

shows results from the Waimānalo Stream section and Figure B shows Kahawai Stream section (n = 2, n = 1 for storm event).

0

2

4

6

8

10

TDNTNNO3+NO2

0

2

4

6

8

10

mg

L-1

a.

b.

Storm Event

Storm Event

82

Vegetation Sampling

Growth and Survival:

Root establishment in the coir logs at the nursery was successfully accomplished

using overhead irrigation and the pre-planted coir log survival rate was 100%. The

success of the coir log installation in stream was affected by the mid-December flooding

event. While this rainfall event occurring 13 days after plant establishment into the new

coir logs, survival rates of three species in the remaining logs were 96, 93, and 79% for,

C. jamaicense, C. javanicus, and C. polystachyos, respectively. Cyperus polystachyos

had a survival rate of 100% in Waimānalo Stream, compared to 57% survival rate in

Kahawai Stream. C. jamaicense had a survival rate of 100% in Waimānalo Stream and

93% in Kahawai Stream. C. javanicus had a 93% survival rate for both Waimānalo and

Kahawai Streams.


An analysis of the data from both streams with a GLM ANOVA revealed that

stream location accounted for the greatest proportion of variance in the tissue N

concentration data (F = 21.55, p < 0.0001) (Table 3.3, Figure 3.6). According to the

ANOVA, species also accounted for a lesser but significant proportion of the data (F =

17.16, p < 0.0001), as did the stream*species interaction (F = 4.38, p < 0.0169). The post

hoc LS means test (P<0.05), indicated that C. polystachos had significantly higher tissue

TN than all other species in Kahawai Stream, whereas C. javanicus had significantly

83

Table 3.3. Results from the combined GLM ANOVA testing mesocosm species tissue TN concentration (%).


Model 5 4.2477 0.8495 11.35 <0.0001

Error 58 4.3418 0.07489


Tissue TN Concentration as Dependant Variable

Species 2 2.5696 1.2848 17.16 <0.0001

Stream 1 1.6135 1.6135 21.55 <0.0001

Species*Stream 2 0.6556 0.3278 4.38 0.0169

84

Figure 3.6. Mean total TN concentrations (percent ± 1 standard error) by species (n = 24, n = 16 for C. polystachyos). Bars with different letters represent significant difference according to Waller-Duncan K-ratio t test (P<0.05).

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

C. jamaicense C. javanicus C. polystachyos

Tota

l N (%

)

Species

a cb

85

lower tissue TN than the other species in both Waimānalo Stream and Kahawai Stream

(Figure 3.9a).

Biomass Growth

After three months in the streams, the minimum value for aboveground biomass

growth was 2.2 g m-2 for C. jamaicense while the maximum growth value was 304.4 g m-

2 for C. javanicus. Across both streams, the GLM ANOVA indicated that species

accounted for the highest proportion of the variance in the biomass data (F = 13.05, p <

0.0001) (Table 3.4, Figure 3.7), with mean species biomass ranging from 16.6 g m-2 for

C. jamaicense and 82.35 g m-2 for C. javanicus. The post hoc test of means (P<0.05),

indicated that Cyperus javanicus had significantly higher mean values within each stream

in comparison to C. jamaicense and C. polystachyos, and showed significant differences

in biomass with greater growth in Kahawai Stream (Figure 3.9b).

86

Table 3.4. Results from the combined GLM ANOVA testing mesocosm species tissue biomass growth (g DW m2).


Model 5 81915.2750 16383.0550 7.05 <0.0001

Error 58 134688.2606 2322.2114


Biomass (g DW m2) as Dependant Variable

Species 2 60623.6169 30311.8084 13.05 <0.0001

Stream 1 238.8834 238.8834 0,10 0.7496

Species*Stream 2 9053.8868 4526.9434 1.95 0.1516

87

Figure 3.7. Mean aboveground biomass (mean ± 1 standard error) of the three plant species. Bars with different letters represent significant differences according to Waller-Duncan K-ratio t test (P<0.05) (n = 24, n = 16 for C. polystachyos).

0

20

40

60

80

100

120


g m

-2

Species

b a a

88

Total N accumulation rates

The combined GLM ANOVA revealed that species accounted for the greatest

proportion of variance in the TN accumulation rates (g TN m-2 yr-1) (F = 6.93, p < 0.02)

(Table 3.5). According to Waller Duncan’s t-test (P<0.05), total tissue TN accumulation

rates C. javanicus were significantly greater than the two other species (Figure 3.8). The

post hoc LS means test (P<0.05) also indicated that C. javanicus had significantly greater

accumulation rates in than the other species in both stream, and the accumulation rate for

C. javanicus in Kahawai Stream indicated only slight significance (P=0.09) over

Waimānalo Stream. (Figure 3.9c).

89

Table 3.5. Results from the combined GLM ANOVA testing mesocosm species tissue TN accumulation rates (g TN m2 y-1).


Model 5 1553842.183 310768.437 4.54 0.0015

Error 58 3974304.982 68522.500

Corrected Total 63 5528147.167 4.54

Tissue TN accumulation (g TN m2 y-1) rate as Dependant Variable

Species 2 945664.7433

Stream 1 44724.4642

Species*Stream 2 236545.0631

90

Figure 3.8. Mean total N accumulation rates (mean ± 1 standard error) by species (n = 24, n = 16 for C. polystachyos). Bars with different letters represent significant difference according to Waller-Duncan K-ratio t test (P<0.05).

0

100

200

300

400

500

600


g T

N m

-2yr

-1

Species

aba

91

Figure 3.9. Mean values of the three species (mean ±1 standard error) in the two stream sections. (a) Total nitrogen (TN) concentrations. (b)Aboveground biomass. (c) Total nitrogen (TN) accumulation rates. Bars with different letters represent significant differences according to the post hoc LSD test of means (P<0.05). (n = 8 in Waimānalo Stream; n = 16, n = 8 for C. polystachyos in Kahawai Stream)

92

0.0

0.5

1.0

1.5

2.0

2.5

Tota

l N (%

)

Waimānalo Stream

Kahawai Stream

0

20

40

60

80

100

120

140

g m

-2

0

100

200

300

400

500

600

700


g T

N m

-2yr

-1

a. b.

c.

a b b b b c

b c ab a a a

a b b b b c

93

Discussion and Conclusions

Water Sampling

Total dissolved N levels in surface water of Kahawai Stream were consistently

higher than levels in Waimānalo Stream. Nitrate+Nitrite accounted for the majority of

TN in both streams, however much more so in Kahawai Stream. This increase is likely

due to the land use in the area being primarily intensified agriculture and greenhouse

nurseries. An increase of TDN was observed in Waimānalo Stream during the December

storm event. These results followed the same patterns reported in Laws and Ferentino’s

(2003) study of Waimānalo Stream, where they acknowledged that the likely sources for

the elevated inorganic N are from animal waste, cesspool seepage, and fertilizer use, and

that high nitrate levels were not surprising given the oxidizing stream environments.

Laws and Roth (2004) considered the effects of stream modification and the hardening of

the stream bed in Waimānalo Stream to which the absence of sediments has shifted

metabolism toward autotrophy and stated that the absence of riparian shading vegetation

has further enhanced this ecosystems deterioration.

Vegetation Sampling

Survival and Growth:

During the nursery pre-planting phase, there was a snail infestation with C.

polystachyos, which required this plant to be replaced due to the heavy grazing of

aboveground biomass. This same type of snail infestation occurred during the mesocosm

experiment, but due to the low number of plants in the mesocosm this problem was

94

controlled by persistent hand removal. Cyperus polystachyos has been reported to have

moderate pest issues (mainly from aphids) (FLC 2001). This snail infestation proved to

be a problem at the nursery, which was likely due to the controlled environment which

lacks predation and allowed snail populations to multiply.

Hawai‘i experiences a wet season from November through April and a dry season

from May through October (Almanac 2009). Major widespread rains account for the

bulk of the precipitation and occur several times during each wet season, but are

infrequent in the dry season. Approximately 50% of the normal annual rainfall occurs in

the three months of December through February, and 80% in the six months of the wet

season; June and July are generally the driest months for most areas (Almanac 2009). In

the original experimental design, coir logs were installed in June to allow roots to

penetrate the logs and anchor plants to the bank before the wet season. Installing logs

and plants in the stream during the wet season was not ideal, and although four out of

twelve coir logs were lost in the December 2008 storm event, plant survival on the

existing logs was successful. The wet season in Hawai‘i experiences shorter day lengths

and increased high cloud cover which may have impeded photosynthetic rates and

biomass growth. The previous mesocosm experiment observed a tremendous increase in

biomasss growth during the spring months. A longer-term stream evaluation which

lasted through the spring and summer months may have shown growth patterns similar to

that of the mesocosm growth in which C. jamaicence would have had the highest

biomass growth.

Survival rates of plants in the coir logs were similar to those observed in the

mesocosm experiment. The high survival rates in the field installation were impressive

95

given the challenging conditions. For example, Waimānalo watershed received a high

intensity rainfall event in mid-December that resulted in a flash flood which exceeded the

holding capacity of the stream. This extreme event occurred only three weeks after coir

log and plant re-installation which tested the plants and their newly establishment roots.

These developing plant roots had not yet penetrated into the riparian substrate and the

coir logs proved to be a valuable method for young plants to rapidly and successfully stay

attachment to the stream bank.


Tissue TN concentration varied widely for the three test species. This

interspecific variability followed similar trends to that of the mesocosm experiment and is

supported by multiple studies (McJannet, Keddy et al. 1995; Tanner 1996; Greenway

1997). Stream location accounted for the greatest proportion of the variability in tissue N

which was likely due to the difference in TN exposure within the two streams, as well as,

to the young age of the plant material. Tissue TN levels from the mesocosm experiment

showed marginally significant correlation with N exposure, which was more pronounced

for C. jamaicense. The young age of planted individuals in stream may have exaggerated

N uptake capacity due to the developing nutrient storage compartments which were still

expanding in young tissues (Tanner 1996). Vegetation nutrient concentrations tend to be

highest early in the growing season, decreasing as the plants mature and senesce

(Vymazal 2007).

Cladium jamaicense responded to the different stream locations with significantly

increased tissue TN tissue concentration in Kahawai Stream. This was supported by its

96

performance across the increasing N treatments of the mesocosm experiment.

Interestingly, C. polystachos developed significantly greater biomass in Waimānalo

Stream than the other species and had significantly higher TN concentration than the

other species in Kahawai Stream. In comparison with stream, survival, and biomass data,

C. polystachos’s exposure to elevated N levels increased its tissue TN concentration and

negatively affected survival rate and biomass growth. This was supported by the

mesocosm results, where C. polystachos had an inverse correlation with biomass growth

and N exposure.

Aboveground Biomass

Biomass growth followed similar trends found in the mesocosm experiment,

where C. polystachyos produced less biomass in the higher N environments and C.

javanicus has high growth across varying N levels. Growth for C. polystachyos was

significantly less in Kahawai than in Waimānalo Stream, with no indication of pest

problems for plants in either stream. Cyperus polystachyos planted outside of coir logs

were observed to proliferate and spread into the riparian zone of Waimānalo Stream.

Erickson and Puttock (2006) describe C. polystachyos as growing well in dry or wet soils,

particularly in open disturbed mesic coastal zones. Cladium jamaicense did not produce

the high biomass results which were observed in the mesocosm experiment. This may be

due to the climatic effect of the wet season or to the short duration of the field

experiment. This also may have been due to the theory that C. jamaicense is adapted to

low nutrient environments (Miao and Sklar 1997; Lissner, Mendelssohn et al. 2003).

Chapin (1980) hypothesized that the physiology of a species adjusted to an infertile

97

environment will have inherently low growth rates as it functions closer to its optimal

growth and metabolic rate. Further investigation of the belowground biomass may reveal

that this species had significant root development and might have emerged with abundant

vegetative growth in the spring, as was observed in the mesocosm experiment.


Mean TN accumulation rate for the three tested species reflected the same pattern

as shown with biomass growth where C. jamaicense and C. javanicus was higher in

Kahawai Stream than in Waimānalo Stream and C. polystachyos showed the opposite

trend. Unfortunately, these plant N accumulation rates represent a short duration in the

stream environment, and may not be representative of the species annual accumulation.

However, recognition that biomass had a strong effect on TN uptake by species was

supported by both the mesocosm and the field experiments. Vymazal (2007) stated that

the potential rate of nutrient uptake by plants is limited by its net productivity (growth

rate) and the concentration of nutrients in the plant tissue. Reddy and DeBusk (1987)

recommend the desirable traits of a plant used for nutrient assimilation and storage would

include rapid growth, high tissue nutrient concentration, and the capability to attain a

high standing crop.

Tanner (1996) discussed how, during initial establishment of plants, net nutrient

storage will be significant in removing N from surface waters. Sartoris’s (Sartoris,

Thullen et al. 1999) constructed wetland study found during the first year when the

vegetation was actively developing an average of 76% of the NH4-N in surface water was

removed, whereas one and one-half years later the mean NH4-N removal dropped to 4%.

98

Chapin (1980) concluded that leaf nutrient content can vary between species on a

seasonal basis. Further investigation into the plant components and of stream nutrient

fluctuations would test generalizations regarding these species TN accumulation rates.

The results of this chapter showed that the higher N concentration in the surface

water of Kahawai Stream were reflected in a higher TN accumulation by C. jamaicense

and C. javanicus and therefore supported hypothesis 3.1 for these species. Hypothesis 3-

1 was partially supported with C. polystachyos, although tissue TN concentration was

significantly higher in Kahawai Stream, there was a significant inverse response between

stream location and biomass growth. Testing these species first in a controlled system

helped to determine species selection while the field portion took into consideration

important installation methods. Bringing the experiment to the field also helped to

illustrate the many challenges which exist when implementing remediation projects,

including land management issues and extreme weather events.

99

Chapter 4: Discussion and Conclusions

As stated in previous chapters, Waimānalo Stream has been recognized as a

waterway which carries sediment and nutrient loads greater than the streams ability to

assimilate them. The ecological impact of this impaired waterway affects not only the

health of the stream, but extends to the receiving waters of Waimānalo Bay. Local

residents need to take caution when using this waterway for recreational purposes

because of the potential health risks associated with polluted waters. The current

management of Waimānalo Stream perpetuates the problems identified in the TMDL by

removing riparian shade vegetation and applying herbicide on a seemingly never-ending

and costly routine ‘maintenance’ schedule (USEPA 1998; USEPA 2001; Laws and Roth

2004). The application of BMPs in the riparian zone of Waimānalo Stream has the

potential to improve water quality, enhance biodiversity, and to support a more

sustainable approach to managing this stream corridor. Planting native species in

coconut fiber coir logs is an innovative BMP that can improve water quality in an

environmentally-friendly, socially-acceptable, and cost-effective manner.

The identification of candidate native sedge species for surface water N uptake

was successfully demonstrated through a mesocosm experiment and field

implementation. The constructed mesocosm was used to determine species responses to

coconut coir log media and to the varying N levels that mimicked the conditions found in

Waimānalo Stream. This seven month trial met the stated objectives with the four

selected species, Cladium jamaicense Crantz, Cyperus javanicus, Cyperus laevigatus,

and Cyperus polystachyos. Hypothesis 2-1, the ability to survive in the coconut coir log

100

medium, was supported for three out of the four species, C. jamaicense, C. javanicus, and

C. polystachyos. Because of their highly successful survival rate, these three species

were selected for use in the field implementation phase. Installing these species in coir

logs in a real stream environment tested their ability to survive in Waimānalo Stream

where they were exposed to the varying hydrologic flow rates and nutrient levels

common to many of Hawai‘i’s streams.

Tissue TN concentration, aboveground biomass, and N accumulation rates varied

widely among the species that were grown in the mesocosm experiment and in the field

installation, supporting hypothesis 2-2a. The significant interspecies variation in nutrient

concentration was supported by other studies that attributed differences to initial

propagule vigor, as well as ecotype growth characteristics (Boyd 1970; Boyd 1978;

McJannet, Keddy et al. 1995; Tanner 1996; Greenway 1997). Biomass growth was an

overriding factor in determining nutrient accumulation rates, as the highest TN

accumulation rates were observed in the species with the greatest biomass growth.

Physiological and developmental differences may have also affected accumulation rates,

as the selected species exhibited variable reproductive behaviors and changing tissue TN

concentrations over time. Miao (1997) found that tissue nutrient concentration is an

integrated expression of many plant functions, such as nutrient uptake, growth defense,

and storage. Hypothesis 2-2b considered that the increased N treatments across

mesocosms would lead to an increase in tissue TN concentration in plants, however this

was not strongly supported as species*treatment effects were marginal. Hypothesis 3-1,

which considered that the heightened N levels in Kahawai Stream would lead to higher

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plant tissue TN concentrations, was strongly supported. Listed below are some specific

points of discussion and conclusions for each of the four species tested in this project.

Cladium jamaicense Crantz

Cladium jamaicense Crantz, also known as ‘Uki in the Hawaiian language, is an

indigenous species commonly found in Hawai’i’s marshlands (Erickson and Pottock

2006). This is a perennial herb in the Cyperaceae family that produces long, thick

horizontal rhizomes. Cladium jamaicense has erect cauline leaves with scabrous margins

that are sharp to the touch and give this species its English name, saw-grass. These plants

are adapted to low resource environments, grow slowly, have low population growth,

long life cycles, low reproductive yield, and respond to resource changes slowly (Miao

and Sklar 1997).

Cladium jamaicense was the most successful species from the mesocosm

experiment in terms of tissue TN concentration, biomass growth, and TN accumulation

rate. Miao and Sklar (1997) and Lissner (2003) found C. jamaicense to have higher

tissue TN values than the competing invasive species in the same area; it was noted by

Davis (1991) that this may be a result of its adaptation to low resource or fluctuating

environments. It has been shown that C. jamaicense has a lesser degree of plasticity

when compared to other species invading its native territory in the Florida Everglades,

has a low demand for nutrients, depends less on a high uptake affinity in an infertile

environment, and has a high retention capacity for acquired resources (Newman, Grace et

al. 1996; Richardson, Ferrel et al. 1997; Lissner, Mendelssohn et al. 2003). During the

three months in the Waimānalo Stream environment, C. jamaicense had the least biomass

102

growth which resulted in the lowest TN accumulation rates. However, tissue TN

concentration for C. jamaicense was greater than C. javanicus in both streams. Despite

this slow initial development in the stream, hypothesis 3 was supported for C. jamaicense

as biomass growth and N accumulation rates were significantly higher in Kahawai

Stream than in Waimānalo Stream. Cladium jamaicense eventually produced the greatest

biomass in the mesocosms, and given enough time in the streams, this species had the

potential to have shown N accumulation similar to the other tested species.

Cyperus javanicus Houtt

Cyperus javanicus, also known as ahu’awa in the Hawaiian language, is a

perennial and facultative wetland species that is found in marshes, streams, ditches, and

taro patches in coastal, cliff-side, and disturbed sites in the Hawaiian Islands (Erickson

and Pottock 2006). During the mesocosm experiment, C. javanicus showed initial

increases in shoot density and within a few months (in April) produced reproductive

material consisting of compound umbels bearing branches of seeds on the tips of large

erect culms. These culms were pounded smooth by the early Hawaiians and used as

cordage and to strain Piper methysticum, also known as ‘awa (Abbot 1992). At the time

of the stream harvest there was no indication of reproductive development with C.

javanicus, in agreement with Brimaecombe’s (2002) study that reported no new

reproductive material for this species was produced between January and April.

Cyperus javanicus produced significantly greater biomass compared to C.

polystachyos and C. laevitagus in the mesocosms, and to C. polystachyos and C.

jamaicense within streams. However, hypothesis 2-2b was not supported for C.

103

javanicus as there were no significant differences in tissue N concentration across

treatment levels in the mesocosms or between stream locations. Cyperus javanicus had

significantly greater tissue TN concentration in Kahawai Stream than in Waimānalo

Stream, which supported hypothesis 3. Interestingly, C. javanicus had significantly

lower tissue TN concentration then the other species in Waimānalo Stream which

followed the same trend as the mesocosm results for C. jamaicense, but not for C.

polystachyos. Although C. javanicus showed the lowest tissue TN concentration in both

streams, the abundant biomass growth resulted in this species having the highest TN

accumulation rates.

Cyperus laevigatus

Cyperus laevigatus, also known as makaloa in the Hawaiian language, is

commonly found on the edges of freshwater, brackish or salt ponds, mudflats and other

sandy coastal areas in Hawai‘i (Erickson and Pottock 2006). The smooth culms were

traditionally used use for finely woven hats and were rated by Sir Peter Buck7 to be the

finest sleeping mats in Polynesia (Abbot 1992). This species has been successfully used

in various remediation efforts across the state (FLC 2001; Van-Dyke 2001). Many of

these projects, which include natural wetlands, golf course ponds, and aboveground

constructed mesocosms, treat wastewater in environments with relatively steady surface

water level. Different media types, such as crushed basalt and ‘bio-barrels’, have been

used for C. laevigatus with varying levels of success (FLC 2001; Van-Dyke 2001). The

type of media used in this project may have accounted for the lack of substantial biomass

achieved in constructed mesocosm coir logs. Arleone Dibben-Young, of Ahupua’a 7 Sir Peter Buck, author of the definitive 1957 study of Hawaiian plaiting.

104

Natives in Moloka’i, has extensive experience with C. laevigatus in the field environment

and stated that this species does not survive even short periods of inundation (personal

communication, July 2008). Hawai‘i’s streams in general are subject to changing surface

levels, especially during the wet season. As demonstrated with the December flood

event, candidate species for stream remediation purposes need to be tolerant of periods of

low flow, as well as, episodic flash flood events. For this reason, as well as the poor coir

log survival rate, C. laevigatus was not considered to be a good candidate for the field

trial. Hypothesis 2-2b was not supported for C. laevigatus in the mesocosm trial.

Cyperus polystachyos Rottb.

Cyperus polystachyos is called ‘Kiolohia’ in the Hawaiian language. It is an

annual or perennial herb which produces flat basal leaf-blades and flowers borne on

many erect stiff culms (Erickson and Pottock 2006). Cyperus polystachos has been used

in wastewater treatment pilot projects (FLC 2001) and has been given a medium score for

tolerance of salt and toxic chemicals and for remediation potential (Paquin, Campbell et

al. 2004). Cyperus polystachos exhibited high survival rates in the mesocosm trial which

supported hypothesis 2-1 for this species. The trends demonstrated in biomass growth

and nutrient uptake by C. polystachos were distinctive when compared with the other test

species in both the mesocosm and field experiments.

In both the mesocosm experiment and in the field, C. polystachos showed an

inverse response to the increased nutrient exposure by producing less biomass.

Hypothesis 2-2b was not supported in the mesocosms for C. polystachos for tissue TN

concentration, biomass growth, or accumulation rate as there was an obvious downward

105

trend across increasing N levels. Hypothesis 3 was both supported and not supported in

the field trial of C. polystachos. A significant response was observed with biomass

growth between stream locations with greater growth in Waimānalo Stream. The

reduced biomass growth in Kahawai Stream combined with the significantly high tissue

TN concentration indicated that this species was sensitive to surface water N loads which

may have affected its growth. It was possible that Kahawai Stream carried surface water

TN levels which exceeded an N threshold for this species and limited its biomass growth.

As seen throughout this study, perhaps the largest effect on the potential rate of nutrient

uptake by plants is its net productivity (Vymazal 2007). Although C. polystachos had

high tissue TN concentrations in Kahawai stream, low biomass growth resulted in quite

low accumulation rates.

Management Considerations

Waimānalo Stream would benefit from management practices that attempt to

utilize ecologically-, socially-, and economically-sound practices. The current

management practice of ‘cut-and-spray’ perpetuates the degradation of this riparian

ecosystem and has potential offsite and downstream effects on other desirable organisms

(i.e. seagrasses, corals) that are harmed by these herbicides (Chapin 1980). Biological

engineering, in this case through the use of pre-planted coconut coir logs, can begin to

restore stream structure and function to address the problem of pollution of surface

waters and underlying issues, such as the loss of biodiversity. Phytoremediation has

shown promise for the treatment of impaired waters in projects locally here in Hawai‘i

and globally. Selection of species for restoration in the field should consider species that

106

will produce abundant biomass and have the ability to store substantial TN in its tissue.

The results of this experiment support the use of certain native species for stream

remediation purposes and the use of the coir log bioengineering method for plant

installation in Hawai‘i’s highly variable stream environment.

107

Appendix A. Mesocosm Weather Data.

Figure A.1. Total daily rainfall (mm) recorded from November 11, 2007 through June 22, 2008.

Figure A.2. Mean daily temperate range (°C) recorded from November 11, 2007 through June 22, 2008.

0

10

20

30

40

50

60

70

80m

m

0

5

10

15

20

25

30

35

°C

Maximum

Minimum

108

Figure A.3. Daily total solar radiation (W/m2) recorded from November 11, 2007 through June 22, 2008.

Figure A.4. Daily mean relative humidity (%) recorded from November 11, 2007 through June 22, 2008.

02000400060008000

100001200014000160001800020000

W/m

2

0

20

40

60

80

100

120

Tota

l RH

%

109

Appendix B.

Table A.1. Chemical composition of the Growmore © 10-8-22 Hydroponic Fertilizer hydroponic fertilizer used in the mesocosm experiment.

Component PercentTotal Nitrogen (N) 10 Ammonical Nitrogen 0.5 Nitrate Nitrogen 3.5Available Phosphate (P2O5) 8Soluble Potash (K2O) 22Calcium (Ca) 4.5Mg 1S 1Boron 0.05CU 0.05Iron (Fe) 0.2Mn 0.1Mo 0.01Zn 0.05

110

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Use of Native Plants and Coir Fiber Logs for Nitrogen Uptake in Waimānalo Stream

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