Mutualism between euryhaline tilapia Sarotherodon melanotheron heudelotii and Chlorella sp.—Implications for nano-algal production in warmwater phytoplankton-based recirculating systems

The West-African euryhaline tilapia, Sarotherodon melanotheron heudelotii shift from visually feeding on zooplankton when juveniles to mostly filter feeding on phytoplankton when adults. When reared using an appropriate ration in intensive aquaculture systems, S. m. heudelotii also consume algal-bas...

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Published in:	Aquacultural engineering Vol. 39; no. 2; pp. 113 - 121
Main Authors:	Gilles, Sylvain, Lacroix, Gérard, Corbin, Daniel, Bâ, Ngansoumana, Luna, Carla Ibañez, Nandjui, Jacob, Ouattara, Allassane, Ouédraogo, Ousséni, Lazzaro, Xavier
Format:	Journal Article
Language:	English
Published:	Amsterdam Elsevier B.V 01-01-2008 [Amsterdam]: Elsevier Science Elsevier
Subjects:	Agnatha. Pisces Algae ammonia Animal aquaculture Animal productions aquaculture systems Biodiversity and Ecology Biological and medical sciences carbon dioxide Chlorella CO 2-limitation detoxification (processing) detritivores dissolved organic carbon Environmental Sciences fish culture fish farms Fish-algae mutualism Fundamental and applied biological sciences. Psychology General aspects intensive farming Marine marine sediments mineralization nitrates nitrification nitrogen phosphates phosphorus Photosynthetic recycling aquaculture system phytoplankton Phytoplankton mass production population density recirculating aquaculture systems Sarotherodon Sarotherodon melanotheron heudelotii Tilapia tilapia (common name) tropics Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution Senegal Phytoplankton mass production Chlorella CO 2-limitation Tilapia Photosynthetic recycling aquaculture system Sarotherodon melanotheron heudelotii Fish-algae mutualism Mass production Algae Carbon dioxide Chlorophyceae Mutualism Environmental engineering Photosynthetic system Vertebrata Chlorophyta Recirculating flow Pisces Phytoplankton CO2-limitation Recycling Euryhalinity Aquaculture tilapia phytoplankton mass production photosynthetic recycling aquaculture system fish-algae mutualism
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Summary:	The West-African euryhaline tilapia, Sarotherodon melanotheron heudelotii shift from visually feeding on zooplankton when juveniles to mostly filter feeding on phytoplankton when adults. When reared using an appropriate ration in intensive aquaculture systems, S. m. heudelotii also consume algal-based detritus, and contribute to sediment mineralization, clean up their environment, and ultimately stimulate and sustain algal growth. We analysed such practical advantages for phytoplankton-based recirculating systems, using S. m. heudelotii and Chlorella sp. as biological material originating from the prototype of such a system operated in Senegal. We performed a 24-h factorial design experiment in 36 tubs, cross-classifying three levels of S. m. heudelotii (fishless control, unfed fish, and fed fish) with four levels of Chlorella initial density. Chlorella overall mean density increased significantly from fishless, to unfed fish, and fed fish treatments, and with Chlorella initial density. S. m. heudelotii did not alter nitrogen nor phosphorus concentrations, only affected by algal initial densities. Most ammonia excreted by fish was probably uptaken by Chlorella. Bacteria-mediated diurnal nitrification was possibly an alternative ammonium loss mechanism at highest oxygen concentrations. Algae were not limited by nitrogen or phosphorus but most likely by low dissolved organic carbon availability. Chlorella differential responses with fed vs. unfed Sarotherodon suggest that CO 2 supplied by heterotrophic S. m. heudelotii respiration played a key role. Observed Chlorella growth rates were similar to the highest rates obtained in algal mass cultures, enriched with CO 2, nitrate and phosphate, under artificial lighting. Our results suggest the existence of a Sarotherodon-Chlorella mutualism in our systems, where S. m. heudelotii provide CO 2, the major limiting factor of Chlorella growth, whereas Chlorella oxygenate and detoxify the water media from ammonia, promoting S. m. heudelotii production. This mutualism could be used to optimize photosynthetic suspended-growth aquaculture systems, particularly in the Tropics where light is abundant and temperature is continuously high.
Bibliography:	http://dx.doi.org/10.1016/j.aquaeng.2008.09.001 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0144-8609 1873-5614
DOI:	10.1016/j.aquaeng.2008.09.001