The Effect of Artificial Vernal Pool Composition on the Population Density and Productivity of...

Running Head: THE EFFECT OF ARTIFICIAL VERNAL POOL COMPOSITION 1

The Effect of Artificial Vernal Pool Composition on the

Population Density

and Productivity of Macroinvertebrates

Rhamy Y. Belayachi, Sahana Ramani, Kritika Singh, Bill. Y. Tang

Thomas Jefferson High School for Science and Technology

THE EFFECT OF ARTIFICIAL VERNAL POOL COMPOSITION

Abstract

Amphibians are sensitive to changes in environmental

conditions. Thus, they are at greater risk of extinction than

other terrestrial vertebrates. Recently, human activity has had a

negative effect on habitats around vernal pools. To mitigate this

problem, the construction of vernal pools is underway. It is

believed that constructed and natural vernal pools have little to

no difference in success of resident and opportunistic species.

We hypothesized that constructed vernal pools would surpass the

natural pool in terms of productivity and egg mass count by a

significant amount determined by a Chi-Square. We marked off an 8

by 21 meter grid and counted the egg masses for each square

meter. We determined the macroinvertebrate diversity by taking

leaf litter samples in the vernal pools. Although certain aspects

of the constructed vernal pool seemed to outperform the natural

pool, the Chi-Square test conducted upon the results showed that

the difference was insignificant. In accordance with the results

and tests, we failed to reject the null hypothesis. The

hypothesis, constructed vernal pools would exceed natural vernal

pools in general effectiveness, was not supported by the results.

2


The Effect of Artificial Vernal Pool Composition on the

Population Density

and Productivity of Macroinvertebrates

Amphibians have the greatest risk of extinction of all the

terrestrial vertebrates (Worldwide Amphibian Declines, 2009).

They are more diverse than mammals or reptiles, and occupy every

terrestrial habitat except Antarctica and the high Arctic

(Alford, 2011). They have a vital role in controlling insect

populations, in nutrient dynamics, and in the cycling of energy

between freshwater and terrestrial systems (Alford, 2011).

Approximately 37% of all amphibians are classified as vulnerable,

threatened, or endangered. (Alford, 2011). The issue of

amphibian decline was first discussed by the First World Congress

of Herpetology in 1989 focusing on reports going back at least 25

years before (Beebee & Griffiths, 2005). Nearly 168 species of

amphibians are believed to have gone extinct in the past two

decades and at least 2,469 (43%) more species are experiencing

declines in population (Sanders, 2012). This indicates that the

number of extinct and threatened species will probably continue

to rise (Wilkinson, 2003).

3


Amphibian population decline is represented greatly in areas

in and around Virginia. This issue is shown by the population

decreases near mining sites (Smithsonian National Zoological Park

[SNP], 2008). For example, in 2007, West Virginia had 30,000

acres of active mountain tops removed (SNP, 2008). This

destruction of salamander habitat has a negative effect on

salamanders, as the habitat can take as long as 70 years to

return to health (SNP, 2008). The overall disturbance also

caused sedimentation downstream, which negatively affected stream

salamanders (SNP, 2008). The percentage of salamanders in nearby

streams went from an increasing trend of 10% to a decline of 30%

(SNP, 2008). In the Appalachian Mountains, it was estimated that

14 million salamanders were lost annually due to human activity

(Habitat Destruction, 2008). In Fairfax County, species of frog,

toad, salamander, and newt are present in moderate numbers

(Fairfax County, n.d.). Although these species are still present,

the numbers are steadily declining due to loss of habitat and

increase in pollution (Fairfax County, n.d.). Apart from decline

in numbers, surviving species are also being poisoned by human

activity. A study done by Kaylor in West Virginia discovered that

4


out of 24 individual salamanders, 6 possessed mutations (Kaylor,

2006). Kaylor’s study found mutations such as missing digits,

head spots, and trail truncation (Kaylor, 2006). Based on the

data acquired, Kaylor deduced that amphibian populations in the

East Coast are not only experiencing decline, but higher rates of

mutation as well (Kaylor, 2006).

Global amphibian population declines have been attributed to

several factors including global warming, increased pollution,

habitat destruction, disease, and the introduction of

opportunistic species. Amphibians are vulnerable to subtle

environmental changes because of their biphasic life cycle

(Wilkinson, 2003). A study conducted using frogs in the Cascade

Mountains proved that subtle shifts in environmental conditions,

such as increases in ultraviolet radiation, affect the

reproduction of frogs (Vitousek, 1994; Howard, 2001). Evidence

that connects amphibian decline to climate change is primarily

based on altered breeding patterns (Beebee & Griffiths, 2005).

There is also evidence that earlier breeding is consistent with

warmer climates (Beebee & Griffiths, 2005). Pollution has also

caused problems like habitat fragmentation, which is the

5


separation of pockets of habitat by major roads or land

development (Wilkinson, 2003). Increased use of pesticides, too,

has created high amounts of pollution resulting in amphibian

population declines (Daszak, Cunningham, & Hyatt, 2000, 2003).

Habitat destruction and deforestation are two of the main causes

of amphibian decline. Newly recognized diseases, such as

chytridiomycosis, have been quickly spreading across amphibian

populations (Daszak et al., 2000, 2003; Berger et al., 1998).

Studies have already indicated the threat this disease poses to

amphibians, with one recording that chytridiomycosis had managed

to render half of native species extinct and leave the other half

at 20% of their prior population levels (Whittaker, n.d.). The

introduction of invasive, exotic species has also been a major

threat to amphibian population growth (Collins & Storfer, 2003).

Numerous invasive species that settle in former amphibian

habitats drive out the amphibians due to increased inter-specific

competition (Collins & Storfer, 2003). Amphibian population

decline is primarily caused by these factors. The construction of

a pool, natural or artificial, can affect the invertebrate

density and productivity. By examining the differences in design

6


between natural and constructed vernal pools, scientists can

obtain an optimal design for pools.

Literature Review

Rogers (1998) conducted an experiment in Folsom, California

to investigate the differences between constructed and natural

vernal pools. His team collected data to compare the invertebrate

richness, opportunist abundance, invertebrate density,

similarity, and productivity of natural and constructed vernal

pools. Over the course of two wet seasons, in 1995 and 1996,

Rogers took six samples of the 37 natural and constructed pools

for comparison. The researchers measured macroinvertebrate

populations by using a fine mesh dip net and estimating the

samples. Invertebrate biomass was found by using volumetric

displacement. Invertebrate density was defined by the number of

individual invertebrates per cubic meter. Similarly, productivity

was defined as the grams of living invertebrates per cubic meter

within the study area. After compiling the data, the Jaccard

Coefficient of Community Similarity and Community Loss indices

were used to determine the similarity between the constructed and

natural vernal pool samples. The study concluded that constructed

7


vernal pools have the capability to match the diversity,

abundance, density, and richness of natural pools.

Ferren, Gale, Hubbard, Parikh, and Wisemen (1998)

investigated the differences between natural and artificial

vernal pools. Their restoration project involved 16 vernal pools

that were created, restored, re-created, or enhanced. The pools

were made using backhoes and skip-loaders in one long depression.

The goal of this project was to preserve and expand the vernal

pools in the Del Sol Reserve in Santa Barbara, California. They

observed the differences in hydrology, native floral and faunal

associations, food chain support, and ability to maintain rare

species. Four parametric and non-parametric measurements of

correlations were computed and used to test plant cover between

natural and artificial pools. Non-metric multidimensional

scaling, a specific type of graph, was used to show the degree of

similarity between the natural and artificial pools. To examine

and count invertebrate samples, a 1 mm mesh D-frame net was used

and the invertebrates were preserved in 70% ethanol, and after

that, counted. The results showed that constructed vernal pools

almost mirrored natural pools.

8


Hypothesis

Previous studies, done by Rogers, Ferren, Gale, Hubbard,

Parikh, and Wisemen indicated that constructed vernal pools

eventually matched their corresponding natural pools in

invertebrate richness, opportunistic abundance, invertebrate

density and productivity. These studies also showed how

constructed pools could eventually match the effectiveness of

their corresponding natural pools. The purpose of our study was

to determine whether the constructed pool, Anchorage Constructed

surpassed or equaled the overall effectiveness of the natural

pool, Anchorage Reference. We hypothesized that constructed

vernal pools would surpass natural pools in terms of productivity

and egg mass count by a significant amount.

Site Description

9


Our different experimental tests were conducted at two

vernal pools in the Elizabeth Hartwell Mason Neck National

Wildlife Refuge. The two

vernal pools we

experimented on were

Anchorage Reference and

Anchorage Constructed

(see Table 1). The Mason Neck

National Wildlife Refuge is a

natural wildlife refuge managed

by the U.S. Fish and Wildlife

Service and contains 921.47

hectares of land (Fish and

Wildlife Service, 2012). It is 28.9 kilometers south of

Washington D.C. The refuge contains 7 kilometers of shoreline

near the Potomac River (Liz Hartwell Environmental Education

Fund, n.d.). Multiple small streams are found in this refuge

along with oak, hickory, and pine trees (Elizabeth Hartwell Mason

Neck National Wildlife Refuge, 2013). The ground is filled with

leaf litter, shrubs, and branches (see Figure 1). The different

Figure 1. Picture of the ground covering

of Anchorage Reference. Shown are the

leaf litter, shrubs, and branches

Table 1. The coordinates of the two vernal

pools we experimented on.

10

Anchorage

Reference

Anchorage

Constructed

N 38o 37’ 52’’

W 77o 11’ 39’’

N 38o 37’ 22’’

W 77o 11’ 16’’


habitats at Mason Neck include freshwater marshes, wetlands, and

small grassland areas (Elizabeth Hartwell Mason Neck National

Wildlife Refuge, 2013). Due to this refuge having the largest

freshwater marsh in Northern Virginia, it is able to support over

44 species of reptiles and amphibians (Elizabeth Hartwell Mason

Neck National Wildlife Refuge, 2013).

Procedures

We made two trips to the Mason Neck site, the first of which

occurred on October 11th, 2012. The purpose of the first trip

made to the Anchorage pool was to set up a grid system over a

portion of the pool, 8 meters by 20 meters. We recorded elevation

measurements, in respect to the base of the transit, which gave

us 100 pieces of data for elevation. We also recorded the amount

of leaf litter and vegetation per square meter. We marked out the

grid area using tape measures and hammered sticks into the ground

at the four corners. Along the perimeter, we placed flags at

every half meter mark. We situated the transit at a selected

corner of the grid, with the transit eyepiece approximately 140

centimeters above the ground. The elevation of the ground

11


directly below the transit was considered zero, and all height

measurements were recorded in respect to that number. To record

the relative elevation, we used poles marked at every 10

centimeter interval up until 240 cm. We set the poles down and

the transit operator read out the number on the pole which lined

up with the eyepiece, elevation-wise. This continued for all 100

square meters. Afterwards, we subtracted approximately 140 cm

from the measurements, to equalize the recordings with the base

of the transit, and then we multiplied the measurements by -1 to

get the true elevation data, as the recorded number was greater

when the ground elevation was lower than the transit, and vice

versa. The leaf litter measurements were measured on a scale

of 0-6, with zero being the sparsest amount of leaf litter, less

than 0.1 inches of litter, and six being the thickest layer,

around 0.6 inches. The vegetation was likewise measured on a

scale of 0-6, with 0 being completely devoid of plants, while 6

would be containing multiple plants. We recorded the vegetation

and leaf litter measurements at a glance, on sight. In order to

determine the general quality of artificially constructed vernal

pools in comparison to natural vernal pools, we needed to compare

12


and contrast multiple aspects of each pool. We first chose the

pools in our study: Anchorage Reference and Anchorage

Constructed. Then, on March 19th, 2013, we made a trip back to

Mason Neck, where we took samples of the many dependent

variables. First, we collected data on egg masses, our first

dependent variable. We marked off an area for study in both

pools, incorporating shallow water and deep water in amounts as

equal as possible. We then divided the area into meter squares

and, we worked through the grid, row by row. In each row, we

searched for the egg masses and recorded the number in each cell.

For each row, we took three sample egg masses and found the mass

using a spring scale in order to measure average productivity.

This was done for 21 rows giving us the average mass of 63 egg

masses. We acquired like data sets from other vernal pools and

other groups within our vernal pool.

Results

We studied the effect of natural, Anchorage Reference, or

constructed, Anchorage Constructed, vernal pools on Ambystoma

maculatum egg mass count and the effect of the pools on

macroinvertebrate diversity. This study was done in order to

13


determine whether the origin of the pool had a significant effect

on the overall effectiveness of it.

Table 2

Egg Mass Count of Anchorage Constructed and Anchorage Reference Vernal Pools

Expected

Referenc

e

Construc

ted

49.5

49.5

Observed

Referenc

e

Construc

ted

59

40

X2

value

p-value

1.82

3

0.056

Xc=3.84

df = 1

α = 0.05

In Anchorage Constructed there were 40 egg masses, in

Anchorage Reference there were 59. Using the degrees of freedom

and p-value in a Chi-Square test, we determined that the

difference between the pools was insignificant (see Table 2). We

14


failed to reject our null hypothesis. The construction of the

pool did not have a significant effect on the amount of egg

masses found. Our p-value, 0.0594, was greater than alpha, 0.05,

which further supported the conclusion that the difference was

insignificant.

Table 3

The Effect of Vernal Pool Composition on the Diversity of Macroinvertebrates

MacroinvertebrateSpecies

Anchorage Reference AnchorageConstructed

Water Flea 3 0

Water mite 1 0

Gilled Snail 1 2

Lunged Snail 1 2

Blood Midge Larvae 244 13

Leech 2 0

True Fly Larvae 0 1

Aquatic Worm 0 14

Beetle 2 0

15


Anchorage Reference had seven species of macroinvertebrates

and Anchorage Constructed had five. Table 3 shows that Anchorage

Reference had higher levels of macroinvertebrate diversity than

Anchorage Constructed. Table 2 shows the different

macroinvertebrate species found in the two vernal pools. The

water flea, water mite, leech, and beetle were found in Anchorage

Reference but not in Anchorage Constructed, whereas, the true fly

larvae and aquatic worm were found only in Anchorage Constructed.

Discussion

The purpose of this study was to determine the effect of

natural versus constructed vernal pool composition on egg mass

count and macroinvertebrate diversity. We hypothesized that

constructed vernal pools would surpass natural pools in both

variables. However, the data we found and the tests we conducted

did not support this hypothesis. This may have occurred because

of nearly identical environmental factors.

Egg masses were more abundant in the Anchorage Reference

natural pool than the Anchorage Constructed pool; however, the

Chi-squared test shows that the difference is insignificant. In

addition, when taking into account the similar climatic features,

16


the possibility of significance due to constructed or natural

origins becomes very low. For instance, the pH of a pool affects

the way an egg clutch grows which determines whether it will

survive or not. Low pH ranges can cause slow salamander embryo

growth which limits the breeding success of the salamanders. Our

primary studies indicated that the pH could influence the

mortality rate of salamander embryos. In addition, the water

quality can affect the types of macroinvertebrates that live in a

habitat. Although pH is critically important to the reproductive

success of salamanders and macroinvertebrates, the pH values for

both pools are extremely close, around 4.5 pH. This negates any

effect on the egg mass count that pH could have had. The other

environmental factors were likewise similar. Thus, given the

near-identical environmental factors, we can draw the conclusion

that Anchorage Constructed matched, not surpassed, Anchorage

Reference in overall efficiency. Our results were consistent with

previous studies done by Rogers (1998) and Ferren, Gale, Hubbard,

Parikh, and Wisemen (1998). Both studies indicated that

constructed vernal pools would eventually match or surpass the

overall efficiency of natural pools. This was supported by our

17


experiment because the statistical difference between the two

pools was insignificant. Our independent variables and dependent

were similar to those of Rogers (1998). Both of our studies

compared the species diversity of the two architecturally

different vernal pools however, they also compared the density,

richness, and opportunistic abundance. Similarly, Ferren, Gale,

Hubbard, Parikh, and Wisemen (1998) compared differences in

hydrology and ecological support for rare species. Both studies

took place in California, in Folsom and Santa Barbara, whereas

ours took place in Virginia. They also compared species other

than Ambystoma maculatum. With a monitored study for a longer

period of time, we would be able to accurately compare our study

with the one done by Rogers and his team, but our short-term

results show that there is no significant difference.

The confounding variables in our study were the ones related

to water quality. The dissolved oxygen, dissolved nitrogen, pH,

temperature could all affect the number of egg masses present in

the pools. Also, the room for human error in our study was great.

With limited time to collect all the data, we had to look through

the rows rapidly. We may have overlooked egg masses in the vernal

18


pool or displaced several egg masses by walking through the

water. Even when using a microscope, it is probable that we left

macroinvertebrate species unaccounted for through the mass amount

of leaf litter present. We were not able to conduct multiple

trials considering that we only had one constructed and one

natural vernal pool.

In the future, it would be beneficial to investigate the

individual effects of pH, temperature, and dissolved oxygen on

the egg masses to be able to relate them between constructed and

natural vernal pools. How is the method of creating constructed

vernal pools similar to the natural process of creating vernal

pools? To further develop and improve this study, in the future

we should have more trials to see if our results are consistent

with other pools. The effect of the architecture of a vernal pool

on the salamander egg count and the macroinvertebrate diversity

was insignificant. The construction of a vernal pool, whether

artificial or natural, has no significant effect on the egg mass

count or macroinvertebrate diversity.

Acknowledgements

19


There are many people that encouraged and helped us with our

study. We would firstly like to thank Mr. Gregory Weiler, the

refuge manager of the Elizabeth Hartwell Mason Neck National

Wildlife Refuge, for allowing us to conduct our study. Without

his cooperation, the study would not have been possible in such

an optimal environment. We would also like to thank our bus

drivers Mrs. Anna Friend and Mr. Scott Marth for transporting our

study groups on repeated trips to and from the refuge. We would

also like to thank the chaperones, parents and teachers, who

accompanied us on our field trips to the refuge and for giving

their time to help out with everything. Finally, we would like to

thank our teachers, Ms. Stephanie Glotfelty, Mrs. Aubrie Holman,

Mr. John LaFever, and Mrs. Tonya Lathom for allowing us class

time to work on our study, for guiding us, for reviewing our

paper, and for answering our questions.

20


References

Alford, R.A. (2011). Ecology: bleak future for amphibians. Nature,

480, 461-462. doi:10.1038/480461a

Beebee, T. J. C., & Griffiths, R. A. (2005). The amphibian

decline crisis: A watershed for conservation biology?

Biological Conservation, 125, 271-285.

http://dx.doi.org/10.1016/j.biocon.2005.04.009

Berger, L., Speare, R., Daszak, P., Green, D.E., Cunningham,

A.A., Goggin, C.L., Slocombe, R., Ragan, M.A., Hyatt, A.D.,

McDonald, K.R., Hines, H.B., Lips, K.R., Marantelli, G.,

Parkes, H. (1998). Chytridiomycosis causes amphibian

mortality associated with population declines in the

rainforests of Australia and Central America. Retrieved

December 16, 2012, from

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC21197/

Collins, J.P., & Storfer, A. (2003). Global amphibian declines:

sorting the hypotheses. Diversity

and Distributions, 9, 89-98.

Daszak, P., Cunningham, A.A. & Hyatt, A.D. (2000). Emerging

infectious diseases of wildlife-

21


threats to biodiversity and human health. Science, 287, 443–

449.

Daszak, P., Cunningham, A.A. & Hyatt, A.D. (2003). Infectious

disease and amphibian

population declines. Diversity and Distributions, 9, in

press.

Elizabeth Hartwell Mason Neck National Wildlife Refuge. (2013,

March 12). [Mason Neck Wildlife Refuge description].

Retrieved March 17, 2013, from http://www.fws.gov/masonneck/

Fairfax County. (n.d.) Amphibians—wildlife. Retrieved December

16, 2012, from

http://www.fairfaxcounty.gov/living/wildlife/species/amphibi

ans.htm

Fish and Wildlife Service. (2012). [Elizabeth Hartwell Mason Neck

national wildlife refuge, VA]. Retrieved March 17, 2013,

from http://www.recreation.gov/recAreaDetails.do?

contractCode=NRSO&recAreaId=1501&agencyCode=127

Ferren, W. R., Gale, N., Jr., Hubbard, D. M., Wiseman, S., &

Parikh, A. K. (1998). Review of ten years of vernal pool

22

http://www.recreation.gov/recAreaDetails.do?contractCode=NRSO&recAreaId=1501&agencyCode=127

http://www.recreation.gov/recAreaDetails.do?contractCode=NRSO&recAreaId=1501&agencyCode=127


restoration and creation in Santa Barbara, California.

Ecology, Conservation, and Management of Vernal Pool Ecosystems, 206-216.

Galvin, S., Hamblet, C., & McKillop, J. (2005). Optimal

environment for egg development in spotted

salamanders. Journal of Ecological Research, (7), 17-21.

Habitat destruction, alteration, and fragmentation. (2008).

AmphibiaWeb. Retrieved December 16, 2012, from

http://www.amphibiaweb.org/declines/HabFrag.htm

Howard, J. (2001). Sensitivity of spotted salamander (Ambystoma

maculatum) embryos to UV-B radiation in Central Virginia.

Retrieved December 16, 2012, from

http://digitalcommons.liberty.edu/cgi/viewcontent.cgi?

article=1021&context=bio_chem_fac_pubs

Kaylor, S.D. (2006). The Breeding Ecology and Natural History of

Ambysomatid Salamanders in an Ephermeral Wetland in Mason

County, West Virginia. Retrieved December 16, 2012, from

www.marshall.edu/etd/masters/kaylor-steven%20-2007-ma.pdf

Liz Hartwell environmental education fund. (n.d.). Retrieved

March 17, 2013, from

23


http://www.hartwellfund.com/masonnecktreasures.html

Rogers, C. D. (1998). Aquatic macroinvertibrate occurrences and

population trends in constructed and natural vernal pools in

Folsom, California. Ecology, Conservation, and Management of Vernal

Pool Exosystems, 224-235.

Sanders, R. (2012). Despite global amphibian decline, number of

known species soars. US Berkeley News Center. Retrieved December

16, 2012, from

http://newscenter.berkeley.edu/2012/07/30/despite-global-

amphibian-decline-number-of-known-species-soars/

Smithsonian National Zoological Park. (2008). Proceedings of the

Appalachian Salamander conservation workshop, by Gratwicke, B.


http://nationalzoo.si.edu/SCBI/SpeciesSurvival/AmphibianCons

ervation/AppalachianSalamanderReport.pdf

Vitousek, P.M. (1994). Beyond global warming: ecology and global

change. Ecology, 75, 1861–

1876. http://dx.doi.org/10.2307/1941591

24


Whittaker, K. (n.d.). Amphibian Population Declines. The Biodiversity

Group. Retrieved December 16, 2012, from

www.biodiversitygroup.org/topics/amphibian_declines.html.

Wilkinson, J. (2003). Declining amphibians. In AccessScience.


http://www.accessscience.com/content.aspx?id=YB030135

Worldwide Amphibian Declines: How big is the problem, what are

the causes and what can be done?. (2009). AmphibiaWeb.


http://amphibiaweb.org/declines/declines.html

25

http://www.thevlm.org/threats-amphibians.aspx

The Effect of Artificial Vernal Pool Composition on the Population Density and Productivity of...

Documents

Transcript of The Effect of Artificial Vernal Pool Composition on the Population Density and Productivity of...