The limnology of Lakes Malawi, Tanganyika, and Victoria is discussed with the objective
of examining how the physical, chemical, and biological properties of the lakes will
determine the response of these ancient great lake ecosystems to human activities.
Of the physical properties discussed, large dilution capacities and long flushing times
can make the detection and removal of chemical pollutants in these lakes difficult.
The outflows of all three lakes are small because of high evaporation losses, and as a
result lake levels are responsive to climate changes that would alter
evaporation : precipitation ratios. Increased nutrient input to these lakes will likely
result in a decrease in the volume of oxygenated water and available fish habitat.
Plankton community composition will also change, probably toward dominance by cyanobacteria.
While the effects of eutrophication on fish production are difficult to predict, changes
in plankton composition would almost certainly be accompanied by changes in fish community
structure. Recent studies of water chemistry and plankton productivity in Lake Victoria
provide evidence of possible eutrophication. Because land use has a diffuse but potentially
large impact on these lakes, conservation strategies must take into account human activities
within entire drainage basins. This requires cooperation between riparian countries and
technological and financial input from the international community. An immediate need is
the establishment of monitoring programs to determine the impact, real or potential, of
human activities around the lakes.