periphyton production in two substrates at different levels of fertilization rate

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Chapter - 7

Periphyton production in two substrates atdifferent levels of fertilization rate


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Chapter - 7 Periphyton production 111 two substrates1. Introduction

Demand for crustaceans and other aquatic organismsincreases, while natural fisheries fastly approaching the optimal levelof exploitation and therefore, aquaculture is the only solution forenhancement of production. The community of microscopic algae thatgrow attached to a variety of submerged substrata is an essentialcomponent of lotic ecosystems. This community, called periphyton, isresponsible for most of the primary production (Mclntire, 1973;Apesteguia and Marta, 1979) and constitutes the food source forseveral invertebrates (Cattaneo et al., 1993). It also plays a major rolein the metabolic conversion and partial removal of biodegradablematerial in ponds and rivers (Lau and Liu, 1993). Microbial food websare integral part for all aquaculture ponds and have a direct impacton productivity (Moriarty, 1997). The term periphyton refers to themicrobial communities living on submerged surfaces, includingbottom sediments, submerged plants and solid natural or man madeunderwater structure. The term periphyton is applied to the complexof sessile biota attached to submerged substrata such as stones andsticks, and includes algae and invertebrates but also associateddetritus and microorganisms. South Asia contributes to about 90% ofthe worlds aquaculture production, the bulk of which is from pondsand rice fields (FAO, 2000). Growth in production is possible byincreased reliance on external resources like fertilizers and feed.Carbon / nitrogen ratio optimization and periphyton development 121


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Chapter - 7 Periphyton production in two substratesBecause of the higher cost of external inputs there is a diminishinginterest among the farmers to continue with the farming practices(0Riordan, 1992). Periphyton based aquaculture through the use ofartificial substrates in the shrimp farms, can improve the efficiency ofconversion of nutrients into harvestable products. The idea ofperiphyton based aquaculture is originally derived from traditionalmethods, such as the padal fishing a unique fishing method in theAshtamudi estuary of Kerala (South India). Locally available treebranches such as mango and mangroves are kept submerged inshallow open water which act as shrimp and fish aggregating devices.A large number of post larvae of shrimps and fish fingerlings findshelter beneath the padals, foraging the peri and epiphyton developedfrom the submerged twigs and other structures used to constructthem (Thomas et al., 2004). Sustainable use of natural resources toenhance the production of low input aquacultme system can help toincrease the income and food security of people in rural areas (NACA,2000). Periphyton based aquaculture can be one of the essentialmeans of increasing shrimp production. The feasibility of periphytonbased systems has been explored in brackishwater fish ponds in WestAfrica (Welcomme, 1972; Hem and Avit, 1994; Konan-Brou andGuiral, 1994) and was found to enhance primary production and foodavailability and increase shrimp production. Trials have demonstratedthat the aquaculture production with additional substrates forCarbon / nitrogen ratio optimization and periphyton development 122


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Chapter - 7 Periphyton production in two substratesperiphyton production is higher than that from substrate free controls(Legendre et al., 1989; Konan et al., 1991; Hem and Avit, 1994; Guiralct al., 1995; NFEP, 1997; Wahab et al., 1999b; Azim et al., 2002). Theexternal resources such as feed and fertilizers supplement orstimulate autochthonous food production in the grow-out system forshrimp growth. In most feed driven ponds, only less than 30% ofnutrients inputs are converted into harvestable products, theremaining being lost to the sediment, effluent water and theatmosphere (Acostra-Nassar et al., 1994; Beveridge ct al., 1994; Olahct al., 1994). Culture systems are also reliant on the environment atlarge to disperse and assimilate waste (Beveridge and Phillips, 1993).

The development of viable low cost technologies and theirapplications to current farming practices would help in enhancingaquaculture production. By providing suitable substrates,heterotrophic food production can be increased which will support theshrimp production. Substrates provide the site for epiphytic microbialproduction which can be eaten by shrimp. The shrimp harvestedmicroorganisms directly in significant quantities, either frommicrobial biofilm on detritus or from naturally occurring flocks inwater column (Schroeder, 1978). There is high variability inperiphyton communities and abiotic factors like light, temperature,nutrient availability or type of substrate. The organisms colonizingsubstrates include microalgae, micro, meio and mesofauna, fungi andCarbon / nitrogen ratio optimization and periphyton development 123


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Chapter - 7 Periphyton production m two SLlDSLral.csbacteria. Most of them are small organisms with short life cycle ofdays or weeks, making the communities highly dynamic andresponsive to environmental changes (Vermaat and Hootsmans,1994). Experiments with artificial substrates have shown thatperiphyton can increase the production of pond harvestable productcompared to systems without substrates (Pardue, 1973; Hem andAvit, 1994; Wahab et al., 1999a, b; Azim et al., 2002; Keshavanathand Wahab, 2001, Keshavanath et al., 2001a, b).This chapter presents the results of the experiments conductedto evaluate the effectiveness of two locally available artificialsubstrates such as Bamboo and Kanchi in the production ofperiphyton under different types of fertilization application in variedlevels. The objectives of this study are shown below:

1. To assess whether the addition of Bamboo and Kanchi asartificial substrates in the grow-outs make any changes inthe optimal water and soil quality requirements of theshrimp.

2. To find out the optimum dosage of fertilizer consortiumapplied in the grow-out for maximum production periphyton.

3. To find out the variation in the suspended and attached algalgrowth in different substrata used for the study.

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Chapter - 7 Periphyton production in two substrates2. Materials and methodsExperimental design

The experiment was carried out in concrete tanks having anreflective bottom area of 6m2. The experimental tanks were filled with auniform sediment layer (7 cm thick) collected from the pokkali shrimpfarm. Lime was added initially at 3 kg tank"1. Bamboo and kanchi(Bambusa sp.) were used as substrate for periphyton growth pluswhile the treatment without substrate was used as control.Experiments were maintained in triplicate following completerandomized design. Cattle dung, urea and super phosphate were usedas fertilizers in this study. In treatment 1C cattle dung, urea andsuper phosphate were applied at the rate of 1500,100 and 50 kg ha'1respectively with out substrate. Whereas the above fertilizers with thegiven dosages with Bamboo substrate is the treatment 1 B while theabove fertilizer dose with substrate kanchi is considered as treatment1 K. Second fertilizer dose of cattle dung 3000 kg ha-1, urea 150 kgha"1 and super phosphate 100 kg ha"1 with substrate bamboo standsfor treatment 2 B while second fertilizer dose with substrate kanchiis the treatment 2 K. In the third fertilizer dose, cattle dung 4500 kgha"1, urea 200 kg ha"1 and super phosphate 150 kg ha-1 respectivelywith substrate bamboo represents treatment 2.5 B while the abovefertilizer dosages with substrate kanchi is the treatment 2.5 K. Thebamboo poles (mean length - 2.0 m the effective water area in 1.5 mCarbon / nitrogen ratio optimization and periphyton development 125


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7 l"CIlpI1yI.UI1 IJILILII-l\.l.&u;; an -..._ __ _and mean diameter 5.5 cm) were vertically planted the pond at adensity of 9 poles m-2 while kanchi were planted horizontally at adensity of 34 poles m4 (mean length - 2.0 m and mean diameter - 1.5cm). Culture tanks were filled with 22 ppt saline water pumped fromthe Cochin estuary which was conditioned for a period of one week.The tanks were drained on the 75" day of experiment.

Water and sediment quality parametersWater quality parameters such as temperature (mercurythermometer), salinity (hand refractometer), transparency (secchidisk) and pH (pH pen) were measured directly from the tank whiledissolved oxygen was measured following Winkler method (APHA,1995) at 09.00 AM on a daily basis. Biweekly water samples werecollected using horizontal water sampler from three locations of eachtank and pooled together. Sediment samples were collected from sixlocations using PVC pipes (2 cm diameter). Sediment and watersamples were collected on biweekly basis between 09.00 and 10.00hours. The water samples were filtered through GF/C Whatman glassfiber filter and the filtrate was analyzed for nitrate-N (cadmiumreduction), nitrite-N and total ammonia nitrogen (TAN) (Phenolhypochlorite method) (Grasshoff et al., 1983). Chlorophyll-a in nonfiltered water column samples were analyzed following standardmethods (APHA, 1995). Biological oxygen demand (5 day BOD) ofCarbon / nitrogen ratio optimization and periphyton development 126


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Chapter - 7 Periphyton production in two substrateswater samples was estimated following APHA (1995). The organiccarbon in the sediment was determined following El Wakeel and Riley(1957). Exchangeable TAN, nitrite-N and nitrateN in the sedimentwere also measured (Mudroch et al., 1996). Total Kjeldahl nitrogen inthe periphyton was estimated (Mudroch et al., 1996). Totalheterotrophic bacteria (THB) count in the water and sediment wasestimated following standard procedures (APHA, 1995) and expressedas colony forming unit (cfu).

Determination of periphyton biomassFrom each tank three poles were selected randomly and 2 x 2

cm? samples of periphyton were taken from different depths per poles.The areas were carefully scraped with the scalpel blade to remove theperiphyton. After the sampling the poles were replaced to the originalplace. The materials collected were pre weighed and dried at 105Cuntil constant weight and kept in dessiccator. The samples are thentransferred to a muffle furnace and ashed at 450C for 6 hours andweighed. The dry matter, acid free dry matter and ash content weredetermined by weight following APHA (1995).

The pheophytin-a concentrations were determined by thefollowing standard method APHA (1995). After the removal, thematerial was immediately transferred to tube containing 10 ml 90%acetone, sealed and transferred to the refrigerator for storingCarbon / nitrogen ratio optimization and periphyton development 127


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Chapter - 7 Periphyton production III Lwu fiuufiuauuoovernight. Samples were homogenized for 30 sec with a tissue grinderand centrifuged for 10 min at 3000 rpm. The supernatant wastransferred to the cuvettes, acidified by addition of three drops of 0.1N HCI and absorption measured for the pheophytin-a.

Study of taxonomic composition of periphyton andplankton

The periphyton samples were taken from randomly selectedpoles from an area of 2 x 2 cmz, each of different depth per pole andpooled together. The samples were collected on biweekly basis afterthe substrate installation. Pooled samples were preserved in 5%buffered formalin and after the vigorous shaking, a 1 ml of subsample was transferred to a Sedgewick-Rafter cell (S-R cell), thenumber of colonies were counted on 10 randomly selected field ofchamber under a binocular microscope (Azim et al., 2001). Theperiphyton sample densities were calculated by the formula.

N= (Px Cx 100)/SWhere N = number of periphyton cells per cm? surface area; P =

number of periphytic units counted in ten fields; C = volume of finalconcentrate of the sample (ml); S = area of scraped surface cm2.

For the taxonomic identification of plankton, the samples werecollected by passing 5 liter of water taken from the four locations ofeach tank and filtered through a 45 p mesh size plankton net. TheCarbon / nitrogen ratio optimization and periphyton development 123


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Chapter 7 Periphyton production in two su usu-atesconcentrated sample was then transferred to a 100 ml measuringcylinder and made up to 100 ml with distilled water. Then thesamples were preserved with 5% formalin solution. The 1 ml ofplankton sub samples were estimated by using Sedgewick-Rafter cell(S-R cell) under the microscope. The plankton densities werecalculated by the formula:

N= (Px Cx 100)/LWhere N = the number of plankton cells per liter of original

water; P = the number of plankton counted in the ten fields; C = thevolume of the final concentration of the sample (ml); L = the volume(liters) of the tank water sample.

Taxa were identified to genus level using keys of Ward andWhipple (1959), Prescott (1962), Belcher and Swale (1976), Bellinger(1992) and Sreekumar (1996).

Statistical analysisStatistical analysis of daily, biweekly and monthly (THB) water,

sediment quality parameters and periphyton biomass (dry matter,pheophytin-a, ash content, protein, nitrogen (%) and ash free drymatter) were done by ANOVA: Two-factor without replicationperformed using Microsoft Excel 2000. The periphyton and planktontaxonomic data were analyzed by SPSS 11.5 One-way Tukey-HSD



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Chapter - 7 Periphyton production in two substratestest. Significant treatment effect was separated by calculating theleast significant difference at 5% level.

3. ResultsWater and sediment quality parameters

The water quality parameters in treatment with or with outsubstrates and fertilization effect were: temperature (30.17 30.83C), dissolved oxygen (6.69 6.81 mg 1'1) and salinity (20.89 - 21.00ppt) and there was no significant difference (P>0.05) among thetreatments. On the other hand, water pH (8.36 8.52), secchi diskreading (56.67 - 62.39 cm) and soil pH (8.29 8.42) have shownsignificant difference (P


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Chapter - 7 Periphyton production in two substrateschlorophyll-a (39.61 - 55.94 pg cm"2) showed significant difference(P


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Chapter - 7 Periphyton production in two substrateswith the dosage levels of fertilization applied indifferent treatments(Fig. 7.2b and c).

Periphyton and plankton biomassPeriphyton biomass recorded from various treatments are

shown in Table 7.3. The results show that there exist significantdifference (P


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Chapter - 7 Periphyton production in two suostratesperiphyton dry matter, no significantly difference (P>0.05) was noticedbetween treatments 2.5 B (1.80 mg cm'2) and 2.5 K (1.76 mg cm'2).However, these treatments showed higher mean dry matter which canbe attributed to the higher levels of fertilization application in thesetreatments. While comparing the periphyton production in thetreatments subjected to the same level of application of fertilizers,bamboo (2 B) showed significantly higher (P0.05) from 2.5 K (Table 7.2).Chlorophyll-a concentrations at different fertilization levels anddifferent sampling periods are shown in Fig. 7.3b. In the case ofpheophytin-a, the highest mean value was recorded in treatment 2 B(1.51 pg cm-2) while it was lowest in 1 K (1.39 pg cm'2). Lowest meanvalue of ash content was recorded in 2.5 K while the highest valuewas in 2 B. In ash free dry matter the highest mean value wasobserved in 2.5 B in contrast to the lowest mean value in 2.5 K (Table7.3).

The genera wise abundance of plankton in control, two types ofsubstrata and varied levels of fertilization are presented in Table 7.4.Although planktons were more abundant at higher levels offertilization, the number of plankton recorded from various treatmentsCarbon / nitrogen ratio optimization and periphyton development 133


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Chapter 7 Periphyton production in two substratesdid not show any significant difference (P>0.05). 69 genera ofphytoplankton belonging to Chlorophyceae (16 genera), Cyanophyceae(6 genera), Cryptophyceae (2 genera), Crysophyceae (10 genera),Euglenophyceae (5 genera), Pyrrhophyceae (14 genera), Rhodophyceae(11 genera) and in zooplankton, Crustacea (5 genera), Rotifer (7genera) were identified, among them Pyrrhophyceae appeared as themost dominant group in the all treatments.

4. DiscussionWater and sediment quality parameters

Improving aquaculture sustainability and its accessibility byintroducing artificial substrates in aquaculture systems is useful inincreasing the surface area for attachment of natural food organisms.The results of the present study showed that the type of substrateused had no significant effect (P>0.05) on temperature, dissolvedoxygen and salinity. The variations in water quality make severeimpacts on shrimp health and survival (Boyd, 1990). For the bestsurvival and growth of shrimp, the dissolved oxygen concentrationabove 4.0 mg 1'1 is essential (Boyd and Fast, 1992; Hall and VanHamm, 1998). In the present study, dissolved oxygen ranged from6.69 - 6.81 mg 1'1 in various treatments. Water pl-I showed significantdifference among treatments and was in the range of 8.36 8.52. Ithas been reported that shrimps become stressed outside their optimalCarbon / nitrogen ratio optimization and periphyton development 134


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Chapter - 7 Periphyton production in two substratespH range of 7.0 9.0 (Boyd and Fast, 1992; Binch et al., 1997 andPhillips, 1998). Both substrate wise and fertilization levels wise,secchi disk reading showed significant difference. Garg and Bhatnagar(1996) observed that ammonia-N, nitrite-N and secchi disk readingshowed increase commensurate with increasing application offertilizer dose and the results of the present study fully concur withthis. Similarly, the inorganic concentration of water and soil alsoshowed an increasing trend with different levels of application offertilizers. In the culture of the experiment, maximum water TANconcentration was observed in treatment 2.5 K with value of 6.41 pg l"1. Weitzel et al. (1979), Stevenson and Stoermer (1982) and Morin andCattaneo (1992) have reported that TAN levels in water were in therange of 24.63 - 68.98 pg 1'1 during periphyton based culture. Theinorganic nitrogen concentration in sediment showed very high valuesin treatments 2.5 K and 2.5 B when compared to other treatments. Itmay be inferred that the high level of fertilization application in 2.5 Kand 2.5 B might have amplified pond productivity which in turncaused the accumulation of inorganic nitrogen in the pond bottom asopined by Bormann et al. (1968), Vitsousek et al. (1979), Schimel andFirestone (1989) and Dail et al. (2001). Sediment nitrite-N and nitrateN level also showed significant increase in treatments having highlevel of fertilization application (2.5 B and 2.5 K). It would thus appearthat the high rate of fertilization application might have promoted theCarbon / nitrogen ratio optimization and periphyton development 135


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Chapter - 7 Periphyton production in two substratesgrowth of organic and inorganic nutrient load in the culture system asreported by Poernomo and Singh (1982), Apud et al. (1989) and Boyd(1989). Interestingly, the soil pH values in treatment 2.5 B and 2.5 Kwere significantly higher when compared to other treatments.According to Dent (1986), Boyd and Teichert-Coddington (1994) andMunsiri et al. (1995) the accumulation of management inputs such asfertilizers and organic matter are responsible for the high soil pH inthe aquaculture systems. Soil pl-I is an important variable and anideal value in the range 6.5 - 8.5 is normally considered as acceptable(Boyd, 1995). High soil pH deteriorates the water quality and affectsadversely the survival and growth of the cultured species (Banerjea,1967; Boyd, 1974).

It is very interesting to observe that there exist an inverserelationship between of total heterotrophic bacteria population andbiological oxygen demand concentration in the culture system duringsampling periods. Moriarty (1997), Remesh et al. (1999) and Umesh etal. (1999) reported that low rate of oxygen in ponds is attributed tothe consumption by the heterotrophic bacterial population. Bell andAhlgren (1987) also strongly agrees with oxygen consumption ofbacteria. The results obtained from the substrate based culturesystem in the present study revealed that there is a direct correlationbetween the level of fertilization application and population ofheterotrophic bacteria in the substrate aquaculture ponds.Carbon / nitrogen ratio optimization and periphyton development 136


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Chapter - 7 Periphyton production in two substratesMiddc-lburg and Nieuwenhuize (2000a), Benner (2002) and Bronk(2002) found that the presence of microbial community may uptakethe different nitrogenous substrates produced in ponds. The uptake ofnitrogen by the heterotrophic bacteria is mostly focused on dissolvedinorganic nitrogen (DIN) form, especially ammonium-N (NI-I4) andnitrate-N (N03-) which are the important nitrogen sources (Antia et al.,1991; Middelburg and Nieuwenhuize, 2000b; Bronk, 2002; Zehr andWard, 2002; Berman and Bronk, 2003). The significant increase inhcterotrophic bacterial population in water and soil resulted in theutilization of inorganic nitrogen concentration which might havehelped in to the plummeting of inorganic nitrogen level in treatmentswhere high rate of fertilization were applied.

The results of the present study revealed that there wassignificant enhancement in the concentration of Chlorophyll-a andorganic carbon in treatments commensurate with increased dosage ofapplication of fertilization (Table 7.2). Dewan ct al. (1991) and Ahmed(1993) reported that the chlorophyll-a concentration showed anincrease with high dosage of fertilization application. According toDoering and Ovitatt (1986), Doering ct al. (1986, 1987) the organiccarbon level showed an increase with the pond production which isfurther dependent on the level of application of fertilizer. Whilecomparing the water and soil quality parameters and level ofapplication fertilizers in various treatments in the present study, itCarbon / nitrogen ratio optimization and periphyton development 137


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Chapter - 7 Periphyton production in two substratescan be concluded that the level of administration of fertilizer in 2 Btreatment was ideal in providing the optimal soil and water qualityparameters when compared to other treatments, followed by 2 K.

Periphyton biomassPrimary and secondary productivity were subjected to very

series studies in extensive aquaculture ponds, particularly in tropicalcountries. The periphyton concentrations were measured by nitrogen(%), dry matter and pheophytin-a concentrations. In the presentstudy, the periphyton biomass was found in Bamboo substrate (2.5 B)followed by 2 B. KonanBrou and Guiral (1994) reported that theperiphton biomass production was very in Bamboo substrate amongvarious substrate studied. The results of present study arecorroborated with KonanBrou and Guiral (1994). According toKeshavanath et al. (2001a) maximum periphytic biomass levelcoincides with the high level of fertilization and among varioussubstrates studied, bamboo was recommended as best substrate forthe substrate based aquaculture. In the present study also higher drymatter was observed in the treatment 2.5 B which was characterizedby high periphyton production, however there was no significantvariation could be observed in treatments 2.5 K and 2 B. It wouldthus appear that the fertilization level can be optimized at 2 B level.Hem and Avit (1994) and Keshavanath et al. (2001a) were of the viewCarbon / nitrogen ratio optimization and periphyton development 133


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that among the available artificial substrate useful for aquaculture,bamboo is far superior for the production of periphyton andincreasing fish productivity. The variation in the values in respect ofdry matter, pheophytin-a, ash content and ash free dry matter indifferent treatments indicate that level of fertilization has animportant bearing on the above parameters. Huchette et al. (2000)reported that the ash content of periphyton show variation amongdifferent levels of application of fertilization. Based on the results ofthe present study, Treatment 2B is very ideal for the high productionand ecological sustainability in aquaculture farms when compared toother treatment studied and therefore can be recommended.According to Makarevich et al. (1993) and Huchette et al. (2000), thetemporal increase in periphyton nitrogen (%), dry matter, ashcontent, pheophytin-a and ash free dry matter can be attributed tothe non grazing effect by organisms. In the present study, no cultureanimals were maintained in the treatments and the results arecomparable to non grazing situation. In the present study 72 generaof periphyton planktons were identified from each treatment. Azim etal. (2002) identified 60 periphyton genera from bamboo based freshwater aquaculture ponds and while comparing the present resultswith that of Azim et al (2002), generic strength of plankton in thepresent study is very high. Conversely, Huchette et al. (2000)identified only 32 species of diatom as periphyton along with otherCarbon / nitrogen ratio optimization and periphyton development 139


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Chapter - 7 Periphyton production in two substratesmicro and microorganisms from both animal and plant kingdoms onartificial substrates in Tilapia cages. The quantity of periphyton variedsubstantially with substrate type, fertilization level, environmentconditions, grazing pressure and taxonomic composition (Paine andVadas, 1969; Heaper, 1988; Makarevich et al., 1993; Napolitano et al.,1996; Ledger and I-lildrew, 1998; Huchettu et a1., 2000; Keshavanathct al., 2001a). Shrimp were absent in this experiment, and there waschance of very minor grazing by zooplankton, mollusks and otherinvertebrates (especially chironomid larvae) possibly in a lower extentas suggested by Huchette et al. (2000). In the present trialmacrobenthic organisms especially chironomid larvae were observedmoving around the surface of the bamboo and kanchi during theperiphyton sampling.

Plankton biomassThe treatments with bamboo as the substrate showed higher

plankton production when compared to other treatments and theplankton production varied with fertilization levels. In the presentstudy, maximum plankton production was observed in 2 B treatmentwhich was significantly higher. Reynolds (1984), Dempster et al.(1993), Delince (1992) established very strong correlation betweenplankton production chlorophyll-a. The results of chlorophyll-a (Table7.2) showed that nutrient concentration (fertilization level) had aCarbon / nitrogen ratio optimization and periphyton development 14()


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Chapter - 7 Periphyton production in two substratesstrong correlation with phytoplankton productivity (Boyd, 1990). Inthe present study, 69 planktons were identified from each treatment.This is very higher when compared to Azim et al. (2002) who reported43 plankton genera from the fresh water aquaculture pond providedwith bamboo as substrate. The phytoplankton production showedsignificant increase due rich nutrient concentration due to the highlevel of fertilization application .In fish ponds, the nitrate-Naccumulates in the systems (Heinsbroek and Kamstra, 1990; Kamstraet al., 1996), however, in the present study, the nitrate-N contentshowed no significant difference in treatments during theexperimental periods. In the present study there was a steadyincrease in the phytoplankton production during the period ofexperiment and this is indicative of the healthiness of the system asopined by Mollah and Haque (1978) Dewan ct al. (1991) and Wahab etal. ( 1999b).

From the practical point of view, the addition of substrates toaquaculture system increases the primary and secondary productiondue to the additive effect of periphyton and phytoplankton basedcomponents of production. Shrimps feed planktonic algae for theregrowth (Johnston et al., 1999; 2000a; 2002). Shrimps generallyrequire food sources such as benthic algae, algal detritus or plantfodder, that can harvested more efficiently (Dempster et al., 1993;Yakupitiyage, 1993).Carbon / nitrogen ratio optimization and periphyton development 141


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Chapter - 7 Periphyton production in two substratesDue to the addition of substrates to water column the algae

growing on substrates, associated bacterial and zooplankton biomassare exploited directly by shrimps (Reynolds, 1984; Prejs, 1984; Horn,1989; Dempster et al., 1995; I-Iuchette et al., 2000). This results inhigher shrimp yield. No negative effect on water and soil quality wasobserved due to the incorporation of artificial substrate. In the presentstudy, the maximum periphyton ash content was observed intreatment 2 B. The periphyton based pond production depends on thenutritional quality of periphyton, grazing efficiency of shrimp,availability of other food source in pond and environmentalconditions.

In Conclusion, for the better periphyton production, bamboo isrecommended as a substrate to fix at water column. The fertilizer dosewith (Treatment 2 B and 2 K) cattle dung 3000 kg ha'1, urea 150kg ha'1, and super phosphate 100 kg ha"1 respectively isrecommended for optimal periphyton growth. Among the periphytonsubstrates, both bamboo and kanchi will not make any adverse effecton water and sediment quality parameters of the grow outs. Thesesubstrates are easily available and are having the advantage of usingrepeatedly for a considerable span. These substrates basedperiphyton production can improve the sustainability and profitabilityof shrimp farming in the country.



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periphyton production in two substrates at different levels of fertilization rate

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