ASPECTS OF COMPARATIVE PLANKTON ECOLOGY IN CASCADING MGENI RIVER RESERVOIRS (MIDMAR, ALBERT FALLS, AND NAGLE): AN OVERVIEW

Summary An overview of a three year study of abundance, community structure and succession of zooplankton and phytoplankton in relation to physical limnological conditions in Lakes Midmar and Albert Falls is presented, along with findings on zooplankton from a nine month study of Lake Nagle. Physical stability increased between Midmar (mean summer N2 = 6.55 × 104 s2) and Albert Falls (N2 = 8.70 × 104 s2), in line with elevations in water temperature. Phytoplankton richness and diversity was similar in these reservoirs, although zooplankton species richness increased downstream. Abundance levels of both phyto- and zoo-plankton were broadly comparable in these two reservoirs. In Midmar and Albert Falls, overall mean (± SD) chlorophyll levels were 3.60 ± 1.54 and 3.41 ± 1.41 μg 11, with corresponding overall average zooplankton standing stocks of 0.85 and 0.76 g m2 dry mass, dropping to 0.54 g m2 in Nagle (for which spring to midsummer data are missing). Ruderal and colonist phytoplankters were persistently ...