Experimental assessment of nutrient enrichment and zooplankton predation effect on phytoplankton community

Tesfahunegny W       

Abstract

Enclosure experiments were conducted over 18 days in December 2011 to assess the effects of zooplankton predation and nutrient enrichment on phytoplankton community composition of Gereb Beati reservoir (Tigray). Enclosures consisted of polyethylene tanks filled with 60 L of filtered water. Experiments were carried out with removal and addition of nutrients cross-classified with the absence and presence of zooplankton, resulting in an experimental design of four treatment levels: (1) no nutrient addition, zooplankton absent, Z0N0 (Control); (2) zooplankton absent, nutrient addition 260 g animal manure per 60 L of sample, Z0N1; (3) no nutrient addition, zooplankton present, Z1N0; and (4) zooplankton present and nutrient added, Z1N1. Four replicates were present for each treatment and samples were collected starting from day 0 up to day 18 with three days interval, up to the end of the experiment. Phytoplankton biomass expressed by chlorophyll a concentration showed 84.7% of the variation and that was also positively associated with turbidity and pH; 7.9% of the variation observed in the second axis was positively associated with zooplankton (D. cf. similis and Moina micrura) and it was negatively associated with Microcystis (t= -4.207; p< 0.000). Seven zooplankton and 15 phytoplankton taxa were identified in the treatments. Nutrient addition (total phosphorus) was more important explanatory variable than zooplankton predation in determining phytoplankton abundance. D. cf. similis were able to suppress Microcystis in enclosures with low nutrient but not in nutrient rich enclosures.


MS Received Date:   2015-12-23  MS Accepted Date:  2016-01-06  MS Published Date:  2016-01-11
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Tesfahunegny W "Experimental assessment of nutrient enrichment and zooplankton predation effect on phytoplankton community" Journal of Zoology Studies 2.5 (2015): 6-17.
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Tesfahunegny, W. (2015). Experimental assessment of nutrient enrichment and zooplankton predation effect on phytoplankton community. Journal of Zoology Studies, 2(5), 6-17.
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Tesfahunegny W. Experimental assessment of nutrient enrichment and zooplankton predation effect on phytoplankton community. Journal of Zoology Studies. 2015; 2(5): 6-17.
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