WWW.WAS.ORG • WORLD AQUACULTURE • DECEMBER 2016 13 This issue’s selected research publication is “Effects of Different Carbon Sources on Bioactive Compound Production of Biofloc, Immune Response, Antioxidant Level, and Growth Performance of Litopenaeus vannamei in Zero-water Exchange Culture Tanks.” The authors are Dahu Zhao, Luqing Pan, Fei Huang, Chao Wang and Wujie Xu and the paper is found in volume 47(4):566-576. This paper is available at the World Aquaculture Society website (was.org) under the Publications tab. Biofloc technology continues to be one of the focal areas of research addressing the goal of sustainable intensive aquaculture. With limited land and water resources for notable expansion of pond production to meet global seafood protein demand, management practices that increase the efficiency of these systems, particularly those with no water exchange, need to be developed and embraced. This study evaluated the effect of management practices, specifically combinations of different carbon sources, on biofloc quality and associated bioactive compounds (carotenoids, phytosterols, polysaccharides, bromophenols, etc.) produced to improve resistance to pathogenic infection. The investigation was conducted in tanks stocked with juvenile Pacific white shrimp at 333/m3. There were four treatments, one with no biofloc (control) and three representing biofloc production from addition of molasses alone (100 percent) and two from combinations of molasses and wheat bran, 50 percent molasses and 50 percent wheat bran, and 75 percent molasses and 25 percent wheat bran. Sufficient amounts of these carbon sources, either as an exclusive source or in different proportional combinations, were added to achieve a C/N ratio of 16. Shrimp were fed three times per day and carbon sources were added once per day. Water samples were collected each day to determine ammonia and nitrite concentrations, and every three days to determine total suspended solids and biofloc volume. At the end of the experiment after 30 days, concentrated biofloc was collected and dried. Contents of carotenoids, polysaccharide and poly-betahydroybutyrate (PHB) in biofloc were determined. Groups of shrimp (8) from each replicate of each treatment were collected and pooled and hemolymph, plasma and hepatopancreas samples were analyzed. Total hemocyte count (THC) in the hemolymph and bacteriolytic and antibacterial activities within the plasma and hepatopancreas were assayed. During the experiment, for all treatments receiving carbon sources, total suspended solids and biofloc volume increased gradually during the first 17 days and then generally leveled out for the duration of the experiment. Levels were significantly higher for the 75 percent molasses and 25 percent wheat bran treatment. The THC in the hemolymph of shrimp collected from all biofloc treatments was greater than that of control shrimp and counts were significantly different among biofloc treatments, with the 100 percent molasses treatment having the highest. The measured bacteriolytic and antibacterial activities of the hemolymph of shrimp from the 100 percent molasses and 50 percent molasses and 50 percent wheat bran treatments were significantly greater than those of control shrimp. Antioxidant activities within the plasma and hepatopancreas of shrimp from all biofloc treatments were significantly greater than those from the control. For the assay of bioactive compounds in the biofloc, PHB content was significantly different among biofloc treatments with the 100 percent molasses treatment having the highest amount and the 75 percent molasses and 25 percent wheat bran treatment having the lowest. Polysaccharide content of biofloc collected from the 100 percent molasses and 50 percent molasses and 50 percent wheat bran treatments was significantly greater than that from the 75 percent molasses and 25 percent wheat bran treatment. No significant difference in carotenoid content of the bioflocs collected from each of the treatments was observed. Shrimp growth in the 50 percent molasses and 50 percent wheat bran treatment was significantly greater than that in the control and all other biofloc treatments. Good water quality for shrimp growth was maintained in tanks of all biofloc treatments. The results of this investigation demonstrate that different individual carbon sources or different proportions of combinations of sources influence the composition of biofloc, and improve the growth and immunological capacity of shrimp. These observations are encouraging but results must be verified in ponds to ensure similar results are observed relative to obtaining the best combination of growth, antioxidant activity, and immunocompetence of shrimp while maintaining excellent water quality. The effects of the different carbon sources observed in this experiment may also be subject to change from seasonal influences. — Louis R. D’Abramo, Section Editor, JWAS A Recent Research Highlight from the Journal of the World Aquaculture Society privilege, and most entertaining to have known him. — Sandra E. Shumway, Groton, Connecticut — Gary H. Wikfors, Milford, Connecticut Anderson, R.A. 2011. Robert Guillard celebrates 90th birthday. The Limnology and Oceanography Bulletin 20(3):54-58. Guillard, R.R.L. 1957. Some factors in the use of nannoplankton Robert Guillard, continued from page 12 cultures as food for larval and juvenile bivalves. Proceedings of the National Shellfisheries Association 48:134-142. Guillard, R.R.L. and Ryther, J. 1962. Studies of marine planktonic diatoms. I. Cyclotella nana Hustedt and Detonula confervaceae (cleve) Gran. Canadian J. Microbiology 8: 229-239. Wikfors, G. 1996. Robert R. L. Guillard Honored Life Member National Shellfisheries Association. Journal of Shellfish Research 15: 533-534.
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