Horizontal differentiation in the limnology of a tropical river-lake (Lake Kyoga, Uganda)
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The Southern and Western water of L. Kyoga is characterised by low mean alkalinities, 1.23±0.08 m eq 1-1; conductivities, 106±5 µS cm-1; pH, 7.2±0.2 and high transparencies, 1.7±0.3 m. In the east, comparatively high alkalinities, 1.96±0.34 m eq 1-1; conductivities, 168±21 µS cm-1; pH of 7.4±0.2 and low transparencies, 0.8±0.2 m are encountered. Hardness varies as closely as alkalinity from 0.6±0.1 m eq 1-1 in the west to 1.0±0.2 m eq 1-1 in the east. SiO3·Si and SO4·S decrease westwards from the eastern lake arms, while NO3·N and PO4·P vary seasonally in the lake, which is mostly saturated with oxygen (86–120%) from the surface to the bottom. Some evidence of polymixis was encountered.
A rich plytoplankton flora occurred with the major groups well represented. Chlorophyceae (37%), Bacillariophyceae (36%) and Cyanophyceae (26%). Synedra spp. (20%). Anabeana spp. (16°10), Nitzschia spp. (10%) were the dominant species groups during July–August 1981. The macrophyte genera Vallisneria, Potamogeton, Nymphaea, Ceratophyllum, Hydrilla occur prominently in the clearer southern lake water. Rotifers and Crustacean Zooplankters found are also recorded. Meroplanktonic crustaceans, chironomids and insects often occur in large numbers.
Key wordsinflows physical chemical warm polymictic plankton macrophytes
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