Photosynthesis, water respiration and growth performance of Litopenaeusvannamei in a super-intensive raceway culture with zero water exchange:Interaction of water quality variables

Luis Vinatea a,*, Alfredo O. Galvez b, Craig L. Browdy c, Al Stokes c, Jesus Venero c, Jason Haveman c,Beth L. Lewis c, Alisha Lawson c, Andrew Shuler c, John W. Leffler c

a Universidade Federal de Santa Catarina, Depto. de Aquicultura, Laboratorio de Camaroes Marinhos, Florianopolis, SC, CEP 88040-900, Brazilb Universidade Federal Rural de Pernambuco, Depto. de Pesca e Aquicultura, Laboratorio de Maricultura Sustentavel, Recife, PE, CEP 52171-900, Brazilc South Carolina Department of Natural Resources, Waddell Mariculture Center, Bluffton, SC, SC 29910, USA

Aquacultural Engineering 42 (2010) 17–24

A R T I C L E I N F O

Article history:

Received 12 November 2008

Accepted 8 September 2009

Keywords:

Water quality

Photosynthesis

Litopenaeus vannamei

Super-intensive culture

A B S T R A C T

Gross and net photosynthesis, and water column respiration of a super-intensive Litopenaeus vannamei

raceway culture with zero water exchange were measured over 21 weeks using the light and dark bottle

method. Spearman correlation analysis was used to explore the relationship of these parameters with

other water quality parameters (O2, temperature, pH, alkalinity, TAN, NO2, NO3, dissolved orthopho-

sphate, turbidity, TSS and VSS) and of shrimp performance based on growth rate and feed conversion

rate. Net photosynthesis generally had negative values, indicating that the system was predominantly

heterotrophic. Gross photosynthesis was significantly related only with VSS, and water column

respiration was related only with turbidity. Shrimp growth rate increased with higher temperature and

dropped with higher pH. Nitrite had a strong inverse relationship with shrimp growth rate (R2 = 0.8044,

p < 0.001) and a weak relationship with FCR (R2 = 0.3319, p = 0.0284). VSS has a significant inverse

relationship with shrimp growth rate (R2 = 0.4989, p = 0.0102) and a direct relationship with FCR

(R2 = 0.5356, p = 0.0162). Photosynthesis and the water column respiration did not seem to have a

significant impact on shrimp productivity.

� 2009 Elsevier B.V. All rights reserved.

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1. Introduction

Aquaculture in general and shrimp culture in particular haverecently been developing strategies of super-intensive cultureswithout water exchange. This approach addresses environmentalquestions raised by both society and the scientific communityregarding sustainable development concepts which demand aconvergence of ecological prudence, economic efficiency and socialequity in all human activities (Bailey, 1988; Brown, 1989; Pruder,1992; Macintosh and Phillips, 1992; Kinkelin and Michel, 1992;Perez, 1993; Currie, 1994; Primavera, 1994; Rosenthal, 1994;Larsson et al., 1995; Kestemont, 1995).

Pioneer work such as Reid and Arnold (1992) and Williams et al.(1996) demonstrated that it is possible to produce shrimp at highdensity in raceway systems that use water recirculation. Therecent progress made in the area of super-dense cultures, alsoknown as ‘‘suspended-growth systems’’ (Hargreaves, 2006) and

* Corresponding author.

E-mail address: vinatea@mbox1.ufsc.br (L. Vinatea).

0144-8609/$ – see front matter � 2009 Elsevier B.V. All rights reserved.

doi:10.1016/j.aquaeng.2009.09.001

‘‘active suspension ponds’’ (Avnimelech, 2006), reinforces the ideathat it is possible to produce aquatic organisms in an intensive andespecially bio-safe way. The absence of effluents, the reduction ofutilized space, and the dramatic reduction of the introduction ofinfectious diseases, are the main criteria for justifying itsdevelopment (McNeil, 2000; McAbee et al., 2003; Burford et al.,2003, 2004; Pruder, 2004; Sowers et al., 2005; Wasielesky et al.,2006; Azim and Little, 2008; De Schryver et al., 2008; Schveitzeret al., 2008).

Although this relatively new aquaculture technology is stilldeveloping (De Schryver et al., 2008), important research effortshave been made with the objective of comprehending the physical,chemical and biological phenomena present in the water thatdictate the dynamic of the cultures (Hopkins et al., 1993; Moss andPruder, 1995; Sandifer and Hopkins, 1996; Davis and Arnold, 1998;Avnimelech, 1999; Browdy et al., 2001). Some studies suggest thatshrimp culture in a closed system (without water exchange) canmaintain water quality considered acceptable for these organisms(Thakur and Lin, 2003). Others suggest that the water quality, inspite of being ‘‘poor’’ due to the large quantity of nutrients that areaccumulated over time, is sufficient to guarantee the growth and

L. Vinatea et al. / Aquacultural Engineering 42 (2010) 17–2418

survival of the animals (Burford et al., 2003). Hargreaves (2006)criticizes the majority of studies regarding these so-called‘‘suspended-growth systems’’, because they suggest that the roleof the bacteria in reference to the maintenance and theimprovement of the water quality is more important than thephytoplankton metabolism.

The importance that primary productivity has in the cultures(extensive, semi-intensive, polycultures, etc.) of different organ-isms is well-documented (Noriega-Curtis, 1979; Laws andMalecha, 1981; Chang and Ouyang, 1988; Yusoff and McNabb,1989; Kadir et al., 2006). However there still exist many doubtswith respect to the role that photosynthesis plays in super-intensive cultures, regarding both level of water quality and thegrowth and well-being of the organisms that are being cultivated.This study contributes to the better understanding of thephenomenon by proposing possible relationships between photo-synthesis, water respiration, shrimp growth and other parametersof water quality present in a zero exchange, super-intensiveshrimp culture.

2. Materials and methods

The present study was conducted at the Waddell MaricultureCenter (South Carolina, Department of Natural Resources, Bluffton,SC, USA) from March to August 2008. A 271 m2 raceway containedwithin a transparent, high-density plastic greenhouse was stockedwith 254,250 PL10 SPF Litopenaeus vannamei (Shrimp Improve-ments Systems Inc., Islamorda, FL, USA) on March 13. Following a43-day nursery period, the growout period began on April 25 atwhich time the population of 1.48 g animals was estimated at165,250 for a density of 610/m2. The shrimp were fed a complete,balanced 35% protein commercial feed (Ziegler Hyper IntensiveRaceway, Ziegler Brothers, Inc., Gardners, PA, USA). The racewayaeration was supplemented by pure oxygen though diffusersstarting with the eighth week of culture. Some solids wereremoved from the water column by an experiment with externalsettling tanks, but this did not significantly alter the total amountof suspended solids (TSS) in the system.

The raceway aeration system consisted of one 5 HP blowerconnected to 60 air stones, and two oxygen generators (40 and140 L) paired with venturi injectors and one 250 L Sweetwater1

oxygen saturation cone. The raceway was also provided with three

Table 1Water quality parameters determined during the experiment and methods used for

the analyses.

Parameter (units) Method

Dissolved oxygen (mg O2/L)a Multiparameter YSI 556 MPS

Temperature (8C)a Multiparameter YSI 556 MPS

Salinity (%)a Multiparameter YSI 556 MPS

Light (mmol photons/m2 s)a Light meter LI COR (LI-1400)b

pHc Multiparameter YSI 556 MPS

Alkalinity (mg CaCO3/L)d Titration method (HCl 0.1 N)

Turbidity (NTU)d La Motte Turbidity Meter 2020

Total ammonium nitrogen-TAN (mg/L)c,e HACH method 8155 (salicylate)

Nitrite nitrogen (mg N-NO2/L)d HACH method 8507

(diazotization)

Nitrate nitrogen (mg N-NO3/L)d HACH method 8039

(cadmium reduction)

Dissolved orthophosphate (mg PO4/L)d HACH method 8114

(ascorbic acid)

Total suspended solids: TSS (mg/L)d EPA method 340.2

Volatile suspended solids: VSS (mg/L)d EPA method 340.2

a Twice daily (morning and afternoon).b Underwater sensor, located 50 cm below water surface.c Once daily.d Once weekly.e NH3 + NH4

+.

O2 cylinders as a backup system. The pure oxygen was suppliedwhen the dissolved oxygen concentration could not be maintainedabove 3 mg/L with simple mechanical aeration.

The water quality control system consisted in measuringdissolved oxygen, temperature, salinity and light twice a day, everyday; pH once a day, every day, and alkalinity, turbidity, TAN, nitrite,nitrate, dissolved orthophosphate, TSS and VSS once a week(Table 1). When the alkalinity was below 60 mg/L, pure sodiumbicarbonate was applied at the rate of 0.12 g/L (a total of 24 kg forthe run), and when the TAN was above 2.0 mg/L, dextrose wasadded at the rate of 0.05 g/L (a total of 22 kg for the run).

Water column respiration and photosynthesis were recordedstarting from the third week of culture, and most physical andchemical parameters were recorded starting from the eighth week.Weekly microscopic examinations identified the main groups ofmicroorganisms present in the water column.

Gross and net photosynthesis and water column respirationwere measured by the classic dark and light bottle method(Strickland, 1960), using the following formulas:

Gross photosynthesis ðmg O2=L hÞ

¼ final O2 of light bottle� final O2 of dark bottle

time ðhÞ

� �

Net photosynthesis ðmg O2=L hÞ

¼ final O2 of light bottle� initial O2 of light bottle

time ðhÞ

� �

Respiration ðmg O2=L hÞ

¼ initial O2 of dark bottle� final O2 of dark bottle

time ðhÞ

� �

Once weekly water from the raceway was collected at a depth of20 cm and placed in triplicate sets of 300 mL glass BOD bottles thatwere either clear or black. Initial and final oxygen concentrations

Fig. 1. Polycarbonate water bath used to measure photosynthesis and water

respiration of a super-intensive Litopenaeus vannamei raceway culture with zero

water exchange by the light and dark bottle method. (A) Water bath with rotating

wheel. (B) 300 mL BOD bottles used in the experiment.

Table 2Main species of microorganisms found weekly in the super-intensive culture raceway of L. vannamei with zero water renewal.

Week Diatoms Chlorophyte Cyanobacteria Dinoflagellates Grazers Other

3 Nanochloropsis sp. Gymnodinium pinque Microciliates

4 Nanochloropsis sp., Dunellia

sp., Chlorella sp.

G. pinque, G. spirale, G. dominans

5 Nanochloropsis sp., Dunellia

sp., Chlorella sp.

Chroococcus sp. Cryptomonas sp.

6 Nanochloropsis sp., Oocystis

sp., Chlorella sp.

Oscillatoria sp. Oxyrrchys marina, G. pinque,

G. dominans

Euplotes sp., Vorticella sp.

7 Nanochloropsis sp., Oocystis

sp., Chlorella sp.

Oscillatoria sp. O. marina, G. pinque, G. dominans Euplotes sp., Vorticella sp.

8 Nanochloropsis sp., Oocystis

sp., Chlorella sp.

Oscillatoria sp. O. marina

9 Nanochloropsis sp., Oocystis

sp., Chlorella sp.

Oscillatoria sp. O. marina Bacteria floc

10 Odentella sp., Centric

diatoms

Nanochloropsis sp., Oocystis sp. Oscillatoria sp.,

Synechococcus sp.

Bacteria floc

11 Nanochloropsis sp., Oocystis sp. Oscillatoria sp., Gymnodinium sp., G. dominans Euplotes sp., Nematoda Small flagellates,

Bacteria floc

12 Nanochloropsis sp. Oscillatoria sp. O. marina, G. pinque Euplotes sp., Microciliates Bacteria floc

13 Nanochloropsis sp. Oscillatoria sp. O. marina, G. pinque Euplotes sp. Bacteria floc

14 Nanochloropsis sp. Oscillatoria sp. O. marina, G. pinque Euplotes sp. Bacteria floc

15 Nanochloropsis sp. Oscillatoria sp. O. marina Microciliates, Nematoda Bacteria floc

16 Nanochloropsis sp. Oscillatoria sp.,

Chroococcus sp.

Ciliates, Euplotes sp., Vorticella sp. Bacteria floc

17 Navicula sp., Thalassiosira sp. Oocystis sp. Oscillatoria sp. Ciliates Bacteria floc

18 N.D. N.D. N.D. N.D. N.D. N.D.

19 N.D. N.D. N.D. N.D. N.D. N.D.

20 N.D. N.D. N.D. N.D. N.D. N.D.

21 Oscillatoria sp., Rotifers, Nematoda Bacteria floc

22 Navicula sp. Oscillatoria sp. Bacteria floc

23 Thalassiosira sp., Navicula sp. Oscillatoria sp. Rotifers, Nematoda, Ciliates Bacteria floc

N.D.: Not determined.

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L. Vinatea et al. / Aquacultural Engineering 42 (2010) 17–2420

were measured with an YSI 5000 digital oxygen meter equippedwith a stirring BOD probe (Yellow Spring Instruments, YellowSprings, OH, USA). Once initial oxygen was recorded, the bottleswere sealed with glass stoppers held in place by plastic lids of thesame color as the bottle. The bottles were attached to a rotatingwheel contained within a 250 L polycarbonate aquarium andincubated for 2 h (Fig. 1). The movement of the rotating wheelsimulated the turbulence within the raceway and insured that themicrobial floc particles in the water column remained insuspension throughout the incubation. One such incubator washoused within the laboratory with artificial metal halide light andelectric heaters in order to create standard conditions of150 mmol photons/m2 s and 28 8C. An identical incubator washoused next to the raceway within the greenhouse with racewaywater pumped through it continuously to maintain the same lightand temperature regime experienced within the raceway. Netphotosynthesis data were useful for verifying the predominanttrophic condition of the raceway’s water column community overtime.

The shrimp growth rate (GR) was established using a randomsample of 100 shrimp, measuring individual weight andsubtracting the mean weight found from the mean weightregistered one week earlier. Feed conversion rate (FCR) wascalculated by dividing the amount of feed offered during a week bythe increase in total biomass from the previous week calculatedfrom growth rate and estimated mortality. The GR and FCR werecalculated, respectively, starting from the eighth and eleventhweek of the culture.

Gross photosynthesis and water column respiration measuredunder raceway and laboratory conditions were compared using a t-test analysis (p < 0.05). This analysis was performed using JMP 5.0statistical software (SAS Institute Inc., Cary, NC, USA). Nonpara-metric Spearman correlation coefficients were calculated to assessthe strength of the association between gross photosynthesis,water column respiration, shrimp growth rate, FCR and each of theother water quality parameters using SigmaStat 3.1 statisticalsoftware (Systat Software Inc., San Jose, CA, USA). The discussion is

Table 3Gross photosynthesis (mg O2/L h), net photosynthesis (mg O2/L h) and trophic condition

and food conversion rate (FCR) found in a super-intensive raceway of Litopenaeus vannam

of equations and not means, so they don’t have a standard deviation).

Week Gross photosynthesis

(mg O2/L h)a

Net photosynthesis

(mg O2/L h)a

Wat

(mg

3 1.51 0.54 (A) 0.94

4 0.84 �0.40 (H) 1.25

5 0.87 0.36 (A) 0.47

6 0.51 0.19 (A) 0.32

7 0.65 �0.29 (H) 0.94

8 0.35 �1.26 (H) 1.48

9 0.37 �1.65 (H) 1.94

10 0.34 �2.29 (H) 2.60

11 1.13 �0.43 (H) 1.49

12 0.73 �0.44 (H) 1.16

13 1.32 0.02 (A) 1.29

14 0.76 �1.10 (H) 1.86

15 1.28 �0.01 (H) 1.25

16 0.49 �0.76 (H) 1.19

17 0.02 �1.06 (H) 1.09

18 0.36 �1.15 (H) 1.51

19 0.19 �0.82 (H) 1.06

20 0.33 �0.93 (H) 1.28

21 0.24 �0.97 (H) 1.25

22 0.38 �0.85 (H) 1.28

23 0.33 �0.56 (H) 0.92

(A) Autotrophic, (H) heterotrophic.a Initial and final oxygen concentrations in the bottles were measured in triplicate

equations.b The same procedure was adopted for these parameters, only differing in the fact t

based only on those variables that showed statistically significantand biologically meaningful relationships. Simple linear regressionanalyses were performed on those pairs of parameters thatresulted in high correlation coefficients. The resulting relationshipswere nitrite concentration versus growth rate and FCR, and nitriteconcentration versus VSS.

3. Results

By August 8 (growout day 105) shrimp had grown an average of1.19 g/week, had a mean individual weight of 19.3 g, and survivalappeared high. A failure of the oxygen delivery system on August 9and 10 resulted in a major mortality event and forced anemergency harvest on August 14. This resulted in a final meanindividual weight of 18.1 g and a survival rate of 40% based on theestimated density at the start of the growout period. Despite thismisfortune, none of the results presented in this paper wereimpacted by the oxygen failure because all measurements,including shrimp growth rates and FCRs, being reported wereconcluded at least a week prior to the event.

The main taxonomic groups of microorganisms found in thewater column are listed in Table 2. Table 3 shows the measuredvalues of gross and net photosynthesis, water respiration, meanweekly weight, growth rate, and food conversion rate of theshrimp.

Gross photosynthesis data did not show significant differencesbetween measurements from the raceway or from the laboratory(t-test, p < 0.05). Similarly, water respiration data were notsignificantly different when measured in the raceway or in thelaboratory.

With regard to net photosynthesis, of the 21 weeks ofobservation, 4 presented positive values (oxygen surplus) and17 presented negative values (oxygen deficit). Table 4 shows thevalues of dissolved oxygen (mg/L), temperature (8C), salinity (ppt),light irradiance (mmol photons/m2 s), pH, alkalinity (mg/L), totalammonium nitrogen-TAN (mg/L), nitrite (mg/L), nitrate (mg/L),dissolved orthophosphate (mg/L), turbidity (NTU), total suspended

(autotrophic or heterotrophic), water respiration (mg O2/L h), growth rate (g/week)

ei with zero water renewal (all the values, except the animals’ weight, are a product

er respiration

O2/L h)a

Weight (g� SD) Growth rate

(g/week)b

FCRb

– – –

– – –

– – –

– – –

– – –

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2.06� 0.07 0.18 –

2.60� 0.20 0.54 1.78

3.27� 0.21 0.68 1.84

4.19� 0.27 0.80 1.39

5.61� 0.28 1.42 1.18

8.51� 0.49 2.90 0.55

10.92� 0.55 2.41 0.68

12.12� 0.52 1.20 1.46

13.24� 0.65 1.13 1.49

14.12� 0.37 1.03 1.47

15.47�1.08 1.34 1.35

17.13� 0.92 1.66 1.09

18.13� 0.41 1.00 2.20

19.32�1.45 1.19 1.19

– – –

but only mean values were used in the respective photosynthesis and respiration

hat each mean value used in the equations resulted from 25 measurements.

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L. Vinatea et al. / Aquacultural Engineering 42 (2010) 17–24 21

solids (mg/L) and volatile suspended solids (mg/L) found in theraceway throughout the observation period.

Table 5 summarizes the significant correlations (Spearman) ofgross photosynthesis, water column respiration, shrimp growthrate and FCR when compared with the other water qualityparameters that resulted in p < 0.05. Considering the water qualityparameters as independent variables, gross photosynthesis wassignificantly related only with VSS and water column respirationonly with turbidity. Shrimp growth rate increased with highertemperature and decreased with higher nitrite, VSS, and pH. Aswould be expected, the FCR increased with higher nitrite and VSS.Nitrite and nitrate concentrations were also positively related withVSS levels.

Fig. 2 demonstrates an inverse logarithmic relationship(R2 = 0.8044, p < 0.001) between nitrite concentration and shrimpgrowth rate, and a weak direct linear relationship (R2 = 0.3319,p = 0.0284) between nitrite and FCR. Nitrite is also directly relatedto VSS (R2 = 0.4243, p < 0.0159) (Fig. 3). VSS also has a significantinverse relationship with shrimp growth rate (R2 = 0.4989,p = 0.0102) and a direct relationship with FCR (R2 = 0.5356,p = 0.0162) (Fig. 4).

4. Discussion

The method for the light and dark bottles (rotating wheelwithin a water bath) used to measure photosynthesis and watercolumn respiration provided good results from a practicalstandpoint. The fact that there were no significant differencesbetween measurements made under field conditions in theraceway and in the laboratory confirms the practicality of routinelymaking those measurements under totally controlled conditions oflight and temperature, independent of weather variability.

The amount of particulate matter suspended in the watercolumn apparently affected the amount of photosynthesis thatcould take place. This is demonstrated by the inverse relationshipbetween VSS and photosynthesis. High levels of particulate matterreduce light penetration and decrease photosynthesis. Theparticulate matter probably also provided considerable substratefor bacteria and other organisms to flourish as demonstrated by thedirect relationship between water column respiration andturbidity.

In this study shrimp growth rate was directly related totemperature, which is understandable since L. vannamei is atropical ectothermal organism with its metabolic rate a function ofambient temperature (Zhang et al., 2006). This has also beendemonstrated in other penaeids like M. japonicus (Chen and Lai,1993), F. chinensis (Chen and Nan, 1993) and F. californiensis

(Villareal and Ocampo, 1993).This experiment seems to confirm reports by Burford et al.

(2004), Cohen et al. (2005) and Brune et al. (2003), thatphytoplankton (and as a consequence, photosynthesis) have onlya limited impact on the growth of shrimp cultivated at highdensities in a closed system. In fact, at least under the observedconditions in the raceway where this study was done, nosignificant relationship between photosynthesis and growth rateor the animal’s FCR was found. Net photosynthesis was usuallynegative, i.e. there was an oxygen deficit, suggesting that theculture was predominantly heterotrophic. If the net photosynth-esis measurements were extrapolated to a 24-h period, there islittle doubt that the culture system operated heterotrophically. Inspite of that, photosynthetic processes were always minima, a factthat was confirmed by the presence of photoautotrophic micro-organisms (chlorophytes, cyanobacteria and dinoflagellates)throughout the duration of the culture.

Nitrogen accumulation in the super-intensive culture systemspresents an important problem to be addressed (Burford and

Table 5Spearman correlation coefficients and probability values (in parenthesis) found among gross photosynthesis (mg O2/L h), water column respiration (mg O2/L h), shrimp

growth rate (g/week) and feed conversion rate with some water quality parameters of a super-intensive zero-water exchange L. vannamei culture.

Temperature pH Nitrite-N VSS Turbidity

Gross photosynthesis – – – �0.792 (0.0010) –

Water column respiration – – – – 0.626 (0.0480)

Shrimp growth rate 0.771 (<0.0001) �0.632 (0.0193) �0.873 (<0.0001) �0.746 (0.0039) –

Feed conversion rate – – 0.703 (0.0145) 0.770 (0.0068) –

Nitrite – – – 0.719 (0.0071) –

Nitrate – – – 0.623 (0.0285) –

L. Vinatea et al. / Aquacultural Engineering 42 (2010) 17–2422

Lorenzen, 2004; Avnimelech, 2006). Thakur and Lin (2003)established that concentrated food supplies between 76% and92% of the nitrogen and that shrimp are able to absorb just 23–31%of this, so the rest that is not absorbed or that is eliminated remainsin the water as organic nitrogen and ammonium (Boyd and Tucker,1998), the latter being highly toxic for animals when found in itsunionized form (Colt and Armstrong, 1981).

In existing aquaculture systems there are three general ways torecycle ammonium nitrogen: photoautotrophic uptake throughmicroalgae, conversion of ammonium nitrogen to nitrate throughthe action of chemoautotrophic bacteria, and ammonium nitrogenconversion directly into the bacterial biomass of heterotrophicbacteria (Ebeling et al., 2006; Hargreaves, 2006). Since norelationship between photosynthesis and total ammonium nitro-gen concentration was found, it is possible that the latter twoprocesses of transformation played the dominant role. It is possiblethat both nitrification and heterotrophic activity could take placesimultaneously on the surface of the floc (Avnimelech, 2006). Infact, the presence of nitrate found in the raceway throughout thestudy is an indication that aerobic nitrification was occurring.These results contrast with Cohen et al. (2005) found in post-larviculture closed production systems (nursery) with densities of

Fig. 2. Regression of the nitrite concentration versus growth rate (A) and food

conversion rate (FCR) of Litopenaeus vannamei (B) in a super-intensive raceway with

zero water exchange.

more than 3000 PL/m3, where photosynthesis and heterotrophictransformation were the main routes of removal of nitrogen beforenitrification processes developed. It is important to emphasize thatin order to confirm these observations for the studies will benecessary, especially with regard to the interaction that existsbetween phytoplankton and bacteria and with regard to the carbonfixation rate (g C/m2 day) realized by phytoplankton (Hargreaves,2006).

Nitrite, an intermediary compound of the nitrification process(Hargreaves, 1998), has significant effects on shrimp performance(Armstrong et al., 1976; Jayasankar and Muthu, 1983; Chen et al.,1990; Lin and Chen, 2003) and in this work deserves specialmention because, of all the parameters it was the one that showedthe highest inverse correlation with shrimp growth rate. Despitereports of a high tolerance of L. vannamei at relatively elevatednitrite concentrations (Lin and Chen, 2003 (27.4 mg N-NO2/L),Handy et al., 2004 (29.0 mg N-NO2/L), Cohen et al., 2005 (26.4 mgN-NO2/L)), the results obtained in this study suggest thatconcentrations as low as 0.72–9.49 mg N-NO2/L were sufficientto significantly reduce shrimp growth rate.

Contrary to the positive relationship that pH seems to have withthe growth of L. vannamei and other shrimp species, such asPenaeus monodon and F. chinensis (Allan and Maguire, 1992; Wanget al., 2002; Zhang et al., 2006), the inverse relationship found inthis study between these parameters could be explained becausethere is greater ammonia toxicity at elevated pH levels (Emersonet al., 1975). However the TAN values recorded apparently did nothave any perceptible relationship with the shrimp growth rate. Inregard to nitrate, Tsai and Chen (2002) confirmed that the level ofsafety of this compound for P. monodon at salinities of 35 ppm is232 mg/L. This would explain why the concentrations of nitrateregistered in the raceway water (113.2 mg/L maximum) seemed tohave no effect on shrimp performance.

VSS concentration was constant with time probably due to thepresence of an equally constant oxidation process. Conversely, TSStended to accumulate because they are less susceptible toheterotrophic microbial degradation, which eventually reflected

Fig. 3. Regression of volatile suspended solids factor (VSS) versus nitrite

concentration (mg N-NO2/L) in a super-intensive raceway culture with zero

water exchange of Litopenaeus vannamei.

Fig. 4. Regression of volatile suspended solids factor (VSS) versus growth rate (A)

and food conversion rate (FCR) of Litopenaeus vannamei (B) in a super-intensive

raceway culture with zero water exchange.

L. Vinatea et al. / Aquacultural Engineering 42 (2010) 17–24 23

in the increase in NTU. However, the dynamics of organic materialin high-density cultures is complex and poorly understood(Hargreaves, 2006). De Schryver et al. (2008) stated that there isno established range with respect to the optimum level of volatilesuspended solids for bio-floc technology culture systems. In thisstudy VSS, with concentrations of 215–450 mg/L, had an inverserelationship with photosynthesis and shrimp growth rate, and adirect relationship with FCR. That is, the larger the concentrationsof VSS the lower the photosynthetic rate of the system, the lowerthe weekly weight gain of the animals and the greater the FCR.With respect to the inverse relationship between VSS and shrimpgrowth rate, it is possible to conclude that in this case theconcentrations of VSS were directly detrimental to the develop-ment of the shrimp. According to Burford and Lorenzen (2004),organic suspended solids affect the animals in both a direct waythrough the demand for oxygen, and an indirect way through theanaerobic formation of toxic metabolites, mainly ammonium andnitrite. This final observation seems to be corroborated by thedirect relationship found in this study between VSS and bothnitrite and nitrate. At least nitrite is a parameter that issignificantly influenced by other factors, including the densityand the type of substrate of the culture (Thakur and Lin, 2003). Thiscalls to attention the fact that no significant relationship of eitherturbidity (20–52.3 NTU) or TSS (403.3–800 mg/L) with growth rateand FCR was observed. Although these parameters have been usedin managing cultivated fish (Avnimelech, 2006), both havesignificant logistical problems, compared to VSS, which limit theirutility in saltwater bio-floc systems.

For the conditions of this study, it is possible to conclude thatphotosynthesis was reduced by increased levels of volatilesuspended solids (VSS), while water respiration increased indirect proportion to turbidity. The final productivity of L. vannamei

during the course of the culture was influenced directly only bytemperature and inversely by pH, nitrite and volatile suspendedsolids. Photosynthesis and water column respiration, in spite ofsignificant relationships with some water quality parameters, didnot have a significant impact on shrimp productivity. It is stronglyrecommended that the same analyses be repeated in future trialsto confirm these observations and to establish possible character-istics shrimp performance and water quality dynamics present inzero water exchange super-intensive shrimp culture.

Acknowledgements

The first and second authors would like to thank the ConselhoNacional de Desenvolvimento Cientıfico e Tecnologico (CNPq-MCT) and to Coordenacao de Aperfeicoamento de Pessoal de NıvelSuperior (CAPES-MEC), both of the Brazilian government, by thepost-doctorate’s grants. Our thanks go to Waddell MaricultureCenter (South Carolina Department of Natural Resources) staff, forall the help offered.

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