Abstract:
Increasing degradation of the water quality,
caused by overuse and salinization, leads to
considerable changes of the phytoplankton composition
in Kenyan Rift Valley lakes. Exemplarily, the
phytoplankton communities and biomasses of deteriorating
freshwater Lake Naivasha and salinizing Lake
Oloidien were studied between 2001 and 2005,
accompanied by physico-chemical measurements
(pH, total phosphorus and nitrogen, alkalinity, conductivity).
Over the last three decades, the ecology of
these two water basins has been subjected to dramatic
changes, caused by excessive use of water and
catchment area by man. In L. Naivasha a shift in
the dominance of coccoid cyanobacteria towards
dominance of Chlorophyceae (Botryococcus terribilis)
was observed. Lake Oloidien exhibited a shift in
the dominance of coccoid Chlorophyceae towards
dominance of cyanobacteria (Arthrospira fusiformis,
Anabaenopsis elenkinii). Phytoplankton findings and
chemical data demonstrate that L. Naivasha has
developed towards a eutrophic freshwater lake while
L. Oloidien has progressed towards a hypereutrophic
alkaline-saline lake.
