Phytoplankton primary productivity seasonality and changes in a small African lake,Lake Hora-Kilole,Ethiopia |
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| Authors: | R Abate D Kifle YH Gao |
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| Institution: | 1. Aquatic Sciences, Fisheries and Aquaculture Stream, Department of Zoological Sciences, Addis Ababa University, Addis Ababa, Ethiopia;2. current address: School of Life Sciences, Xiamen University, Xiamen, China.;3. School of Life Sciences and State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China |
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| Abstract: | The seasonality of primary productivity by phytoplankton in relation to physico-chemical and biological variables was studied in Lake Hora-Kilole from August 2007 to May 2008. In 1989, the Mojo River was temporarily diverted to flow into the lake, which substantially changed its physico-chemical conditions and the composition of the phytoplankton. Primary productivity was controlled primarily by soluble reactive phosphorus (SRP), ammonia (NH3), temperature and euphotic depth (Zeu). The light-saturated rate of photosynthesis (Amax) varied from 370 to 3 843?mg O2 m?3 h?1 with the maximum value corresponding to the seasonal maximum of phytoplankton biomass. Compared to the period before the diversion of the river, Amax was reduced by more than ninety-fold in early 1990s and by less than five-fold in 2007 and 2008. Similarly, average phytoplankton chlorophyll a was reduced by more than 2.5 × in the early 1990s and to less than 50% in 2007 and 2008. This highlights the importance of the diversion river water on the physico-chemical and biological environment of the lake. |
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| Keywords: | chlorophyll a environmental variables phytoplankton abundance seasonal dynamics zooplankton |
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