Use of Selected Periphyton Species to Improve the Water Quality and Shrimp Postlarval Production

In marine shrimp larval rearing practices, a large amount of water has to be exchanged frequently in order to maintain good water quality. This procedure contributes to the eutrophication of aquatic environment due to flushing of nutrient-enriched waters from aquaculture facilities. Furthermore, the process of frequent water exchange will eventually result in lack of good water supply which can also increase the risk of diseases in the hatchery. To overcome eutrophication and the risk of diseases, an alternative eco-friendly method was investigated to decrease harmful compounds especially ammonia and nitrite by using periphyton grown on substrates. Different periphyton species (Oscillatoria, Navicula sp., Cymbella sp. and Amphora sp.) from marine shrimp culture ponds were isolated, purified and mass cultured in the laboratory and grown in Conway medium. The effects of salinity (0, 15, 20, 25, 30 and 35 ppt) on the growth of these genera under aboratory condition was determined. The highest (p<0.05) growth was achieved at 25-35 ppt salinity. Nutritional composition of different periphyton genera were analysed to determine their importance as shrimp feed. All periphyton genera contained high protein (Oscillatoria 42%, Cymbella 43%, Navicula 49% and Amphora 44% of dry wt.), lipid (Oscillatoria 20%, Cymbella 26%, Navicula 26% and Amphora 23% of dry wt.) and carbohydrates (Oscillatoria 24%, Cymbella 20%, Navicula 11% and Amphora 18% of dry wt.). The periphyton genera also contained of docosahexaenoic acid (DHA) (Navicula 2%, Cymbella 2%, and Amphora 3%, Oscillatoria 1% of total lipid) and ecosapentaenoic acid (EPA) (Amphora 15%, Cymbella 3%, Navicula 8% and Oscillatoria 1% of total lipid). Periphyton colonization using different substrates (bamboo, polyvinylchloride pipe, plastic sheet, fibrous scrubber and ceramic tile) in intensive shrimp culture ponds were studied for a period of 60 days. Nineteen periphyton genera dominated by the Chlorophyceae colonized the substrates during the first 15 days. Periphyton colonization on bamboo showed the highest biomass (p<0.05) amongst all the substrates used. Biomass of periphyton in terms of chlorophyll-a varied from 179 to 1137 μg m-2 with mean values of 1137 ± 0.6, 929 ± 0.6, 684 ± 1.2, 179 ± 0.6 and 658 ± 0.6 μg m-2 on bamboo, polyvinyl chloride (PVC) pipe, plastic sheet, fibrous scrubber and ceramic tile respectively on first 15 days. Effectiveness of different periphyton genera in reducing total ammonia nitrogen (TAN), nitrite nitrogen (NO2–N) and soluble reactive phosphorous (SRP) in hatchery tanks without shrimp postlarvae were studied for a period of 16 days. It was found that Oscillatoria significantly reduced (p<0.05) TAN (90%), SRP (83%) and NO2–N (91%) whereas diatom species decreased 60%, 74% and 78% of the same parameters respectively. In addition, Oscillatoria yielded the highest (p<0.05) biomass compared to other periphyton species. Results of this study showed that all the periphyton genera were able to significantly reduce TAN, SRP and NO2-N concentrations in larval rearing tanks. The use of periphyton coated substrate (periphyton grown on polyvinylchloride pipes) for improving water quality and survival of shrimp postlarvae in hatchery without water exchange was studied for a period of 16 days. Periphyton species significantly reduced (p<0.05) TAN in shrimp culture tanks as compared to the control (without periphyton coated substrate). Amongst the treatments, tanks with Oscillatoria had the lowest mean TAN (0.09 ± 0.00 mg L-1) compared to tanks with diatoms (3.77 ± 0.17 mg L-1) and the control (5.17 ± 0.08 mg L-1). Similarly, NO2–N (0.04 ± 0.00 mg L-1) and SRP (0.22 ± 0.00 mg L-1) concentrations were significantly (p<0.05) lower in the shrimp culture tanks with periphyton species than the control (4.13 ± 0.24 mg L-1). Shrimp cultured with periphyton coated substrate showed significantly higher survival (51% - 60%) than those without periphyton (37%). In addition, the shrimp postlarvae produced in this system showed high resistance to reverse salinity stress test (37% - 43%) compared to the control (26%). This study illustrated that beneficial Periphyton species could improve water quality, provide live feed and serve as refugium for the shrimp postlarvae

Biological approaches in management of nitrogenous compounds in aquaculture systems.

Aquaculture is the fastest growing food-producing sector accounting for almost 43% of the world's food fish. There is however a need to increase aquaculture production in the next two decades in order to satisfy the minimum protein requirement for human nutrition. There are many constraints that limit the maximum production in aquaculture systems such as water quality and adequate live feeds. With the development of modern aquaculture farming, extensive culture has given way to intensive culture systems. In intensive systems, cultured organisms are fed protein-rich formulated feeds. Uneaten feed along with metabolic wastes and other organic matters decompose resulting in an increase of toxic nitrogenous compounds causing deterioration of water quality which is toxic to cultured organisms. The discharge of a large amount of nutrient-rich wastes from these aquaculture systems, the majority of which are nitrogenous compounds, promotes eutrophication in water bodies. In general, an increase of nitrogenous compounds has adverse effects on the environment and on aquaculture production. The aim of this paper is to highlight some of the trends in biological management of nitrogenous substances in aquaculture systems

Use of periphytic cyanobacteria and mixed diatoms coated substrates for improving water quality, survival and growth of Penaeus monodon postlarvae in closed water hatchery system

An eco-friendly method was established by using periphyton coated substrate (a cyanobacterium or mixed diatoms) to improve water quality, survival and growth of Penaeus monodon postlarvae (PL) in a shrimp hatchery system without changing water. Polyvinyl chloride (PVC) pipes (2 cm×2 cm) were used as the substrate to grow pure cultures of cyanobacterium and diatoms. P. monodon (PL1)were cultured in 40 L glass tanks containing 30 L filtered-seawater and stocked at a density of 50 PLs L−1. Two treatments using i) cyanobacterium coated substrate (Oscillatoria), ii) mixed diatoms coated substrate (Amphora, Navicula and Cymbella), and a control(without substrate) were employed in this experiment. The experiment was run in triplicate for a period of 16 days (PL16) whereafter the PLs are normally stocked in growout ponds. Tanks with Oscillatoria coated substrate had the lowest (Pb0.05) concentrations of total ammonia nitrogen (TAN, 0.03±0.0mg L−1); nitrite–nitrogen (NO2–N, 0.01±0.0 mg L−1) and soluble reactive phosphorus (SRP, 0.05± 0.0 mg L−1) in comparison tomixed diatoms (0.82±0.02; 0.52±0.05; 0.35±0.01 mg L−1 for TAN, NO2–N and SRP, respectively) and control tanks (1.14±0.01; 0.80±0.02; 0.53±0.04 mg L−1 for TAN, NO2–N and SRP, respectively). In addition, nutrients in diatoms treated tanks were significantly lower (Pb0.05) than the control. Oscillatoria was more effective in reducing TAN (1.40 g m−2 day−1), NO2–N (0.07 g m−2 day−1) and SRP (0.06 g m−2 day−1) than the mixed diatoms. Furthermore, shrimp cultured in tanks containing periphyton coated substrate showed significantly higher survival (51.3±0.6%–60.0±1.1%) than those reared in the periphyton free control tanks (36.8±0.3%). The specific growth rates (dry weight) of the PLs was the highest in the diatoms tanks (28.02±0.01%)followed by the Oscillatoria (22.83±0.03%) and the control tanks (19.83±0.05%) (Pb0.05). The PLs produced in both substrate based systems exhibited higher resistance to reverse salinity stress test than those reared in the control tanks (36.7±4.1 to 43.3±8.2%survival compared to 26.7±8.2%) (Pb0.05). The protein, lipid and carbohydrate levels in PLs reared in tanks with mixed diatoms coated substrate were higher than for PLs grown in control tanks. This study illustrated the beneficial effects of periphyton coated substrate in improving water quality, growth and survival of shrimp larvae grown in shrimp hatchery system without water exchange

Use of microalgal-enriched Diaphanosoma celebensis Stingelin, 1900 for rearing Litopenaeus vannamei (Boone, 1931) postlarvae

The present work investigates the effects of Chaetoceros calcitrans, Nannochloropsis oculata, Tetraselmis tetrahele and Isochrysis galbana diets on the lifespan, growth, neonate production and the nutritional profile of Diaphanosoma celebensis. In addition, the effects of enriched D. celebensis on the survival and growth of Litopenaeus vannamei postlarvae (PLs) was compared with Artemia. Results showed that significantly higher (P 0.05) from PL fed only Artemia, indicating that D. celebensis has potential to be used as live feed for the hatchery rearing of L. vannamei PLs, in place of Artemia. This study illustrated that the quality of the D. celebensis production and proximate composition was highly correlated with the food type, and it can be used as a valuable live feed for shrimp larviculture

Antibiotic resistant Salmonella and Vibrio associated with farmed Litopenaeus vannamei

Salmonella and Vibrio species were isolated and identified from Litopenaeus vannamei cultured in shrimp farms. Shrimp samples showed occurrence of 3.3% of Salmonella and 48.3% of Vibrio. The isolates were also screened for antibiotic resistance to oxolinic acid, sulphonamides, tetracycline, sulfamethoxazole/trimethoprim, norfloxacin, ampicillin, doxycycline hydrochloride, erythromycin, chloramphenicol, and nitrofurantoin. Salmonella enterica serovar Corvallis isolated from shrimp showed individual and multiple antibiotic resistance patterns. Five Vibrio species having individual and multiple antibiotic resistance were also identified. They were Vibrio cholerae (18.3%), V. mimicus (16.7%), V. parahaemolyticus (10%), V. vulnificus (6.7%), and V. alginolyticus (1.7%). Farm owners should be concerned about the presence of these pathogenic bacteria which also contributes to human health risk and should adopt best management practices for responsible aquaculture to ensure the quality of shrimp

Antibacterial activity of neem (Azadirachta indica) leaves on Vibrio spp. isolated from cultured shrimp.

The use of antibiotics in aquaculture to treat infections has resulted in the development of resistant strains which have rendered antibiotic treatment ineffective. Therefore, alternative antibacterial materials must be found. Extracts of neem tree (Azadirachta indica) leaves were tested against Vibrio parahaemolyticus and Vibrio alginolyticus isolated from cultured shrimp. Aqueous extract of neem leaves did not produce any inhibitory zone while the neem juice produced inhibitory zone that showed linear relationship to the concentration of neem juice on both bacteria. The Minimum Inhibitory Concentration (MIC) for V. parahaemolyticus and V. alginolyticus was 3.13 and 6.25%, respectively. The Minimum Bactericidal Concentration (MBC) for V. parahaemolyticus and V. alginolyticus was 12.50 and 25.00%, respectively. It is concluded that neem juice is an antibacterial agent and is useful for inhibition of vibrios in shrimp

Availability and utilization of pigments from microalgae

Microalgae are the major photosynthesizers on earth and produce important pigments that include chlorophyll a, b and c, β-carotene, astaxanthin, xanthophylls, and phycobiliproteins. Presently, synthetic colorants are used in food, cosmetic, nutraceutical, and pharmaceutical industries. However, due to problems associated with the harmful effects of synthetic colorants, exploitation of microalgal pigments as a source of natural colors becomes an attractive option. There are various factors such as nutrient availability, salinity, pH, temperature, light wavelength, and light intensity that affect pigment production in microalgae. This paper reviews the availability and characteristics of microalgal pigments, factors affecting pigment production, and the application of pigments produced from microalgae. The potential of microalgal pigments as a source of natural colors is enormous as an alternative to synthetic coloring agents, which has limited applications due to regulatory practice for health reasons