Abstract
AEI Aquaculture Environment Interactions Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AEI 9:73-85 (2017) - DOI: https://doi.org/10.3354/aei00213 FEATURE ARTICLE Sunlight and sediment improve the environment of a litter biofilm-based shrimp culture system Charles Gatune1,*, Ann Vanreusel2, Marleen De Troch2 1School of Natural Resources and Environmental Studies, Karatina University, PO Box 1957─10101, Karatina, Kenya 2Biology Department, Marine Biology, Ghent University, Campus Sterre, Krijgslaan 281-S8, 9000 Ghent, Belgium *Corresponding author: kgatune@yahoo.com ABSTRACT: In silvofishery, where shrimp culture is integrated with mangrove trees, the mangrove leaf litter may modify the environment in these culture systems. This study tested the potential of submerged leaf litter of Rhizophora mucronata and associated biofilm in providing a favorable environment for post-larval shrimp Penaeus monodon. Litter decomposition and assembly of microalgae and epifauna were assessed under exposure to sunlight or shade, and presence or absence of sediment. Litter incubated with sediment and exposed to sunlight was rapidly decomposed and supported the highest biomass and diversity of microalgae and epifauna. The litter also supported the highest abundance of diatoms, polychaetes and nematodes during the 4th week of decomposition. Cyanobacteria of the genus Microcystis dominated litter incubated without sediment, in sunlight, after decomposition for 5 wk. Under shaded conditions, diatoms of the genus Navicula and the Cyanobacteria Anabaena spp. and Oscillatoria spp. continued to grow at high total ammonium nitrogen, low dissolved oxygen, low temperature and low pH. Our study illustrates synergy between sediment and direct sunlight in promoting diversity of microalgae and polychaetes (of dietary benefit to shrimps), inhibiting growth of Cyanobacteria and maintaining water quality at levels favorable to culture of post-larval shrimp. Our findings support 4 practices for a healthy environment in fish ponds: (1) locating ecological shrimp culture in less forested areas, (2) promoting sediment conditions in artificial shrimp culture systems, (3) exposing litter-derived biofilm within ponds to sunlight and incubating with sediment to maintain favorable water quality and control Cyanobacteria blooms, and (4) minimizing the use of pond liners and related sludge removal. KEY WORDS: Shrimp culture · Sunlight · Sediment · Mangrove litter · Microalgae · Epifauna · Biofilm Full text in pdf format Information about this Feature Article PreviousNextCite this article as: Gatune C, Vanreusel A, De Troch M (2017) Sunlight and sediment improve the environment of a litter biofilm-based shrimp culture system. Aquacult Environ Interact 9:73-85. https://doi.org/10.3354/aei00213 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AEI Vol. 9. Online publication date: February 08, 2017 Print ISSN: 1869-215X; Online ISSN: 1869-7534 Copyright © 2017 Inter-Research.
Highlights
The importance of decomposing mangrove leaf litter in providing natural food to post-larvae of penaeid shrimps lies mainly in the associated periphytic biofilm (Gatune et al 2012)
Mangrove leaf litter incubated with sediment and exposed to direct sunlight recorded the highest percentage weight loss during the 7th week of decomposition, and was significantly more decomposed compared to litter incubated without sediment and in the Duration of decomposition (Week)
Decomposing mandecomposed for < 6 wk was not significantly different grove litter exposed to sunlight supported signifiin all treatments (p > 0.05), except for the treatment cantly higher abundance of epifauna compared to exposed to sunlight in the absence of sediment, which differed significantly during the 7th week of litter incubated in the shade (p = 0.002)
Summary
The importance of decomposing mangrove leaf litter in providing natural food to post-larvae of penaeid shrimps lies mainly in the associated periphytic biofilm (Gatune et al 2012). Our previous studies revealed that the biofilm developing on decomposing litter possesses potential and direct nutritive value to post-larval shrimp (Gatune et al 2012, 2014a, 2014b) These studies identified strategic intervention timelines in managing mangrove litter falling into silvo−shrimp aquaculture systems. Ecological shrimp aquaculture in mangrove systems has gained environmental support because of its tendency to conserve the mangrove forest (Primavera 1998, Fitzgerald 2000) by rearing fish without clearing mangrove trees (Primavera 1998) This integrated approach implies that the shrimp culture system constantly intercepts mangrove litter fall, which proceeds to decompose under the influence of the microbiota present in the biofilm (Benner & Hodson 1985, Rajendran & Kathiresan 2007). Light intensity increases algae biomass, density and composition, creating a rich energy source for shredders, which enhances the rate of plant litter decomposition by their grazing activity (Franken et al 2005)
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