Article

Phytoplankton primary productivity seasonality and changes in a small African lake, Lake Hora-Kilole, Ethiopia

Published in: African Journal of Aquatic Science
Volume 42, issue 3, 2017, pages: 259–269
DOI: 10.2989/16085914.2017.1361712
Author(s): R AbateAquatic Sciences, Fisheries and Aquaculture Stream, Department of Zoological Sciences, China, D KifleAquatic Sciences, Fisheries and Aquaculture Stream, Department of Zoological Sciences, Ethiopia, YH GaoSchool of Life Sciences and State Key Laboratory of Marine Environmental Science, China

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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