Biodiversity of a Tropical Reservoir, South-Eastern Lowveld, Zimbabwe : Population dynamics, communities and impact of water level fluctuations

The study provides the first record of a limnological investigation of the Malilangwe reservoir, situated in the south-eastern lowveld of Zimbabwe. Most reservoirs of comparable size spill annually but the Malilangwe reservoir has not spilled in nearly 11 years making it a unique system. Water quality varied both spatially and temporarily in accordance with water level fluctuations. A total of 98 phytoplankton species and 68 zooplankton species were recorded. Variation in macrophyte species composition, distribution and abundance identified 13 species representing 8 families. Change of seasons and water level fluctuations caused successional changes in macrophyte community structure from the dominant emergent macrophytes. A macroinvertebrate community assessment identified forty-two families.A fish diversity fauna survey done in Malilangwe reservoir, Chiredzi and Runde Rivers, Hippo Valley swamp and irrigation channels found a total of 36 fish species belonging to 11 families with 8 species from 5 families being recorded from the reservoir. Tilapia rendalli was of conservation significance in the reservoir as its habitat was being severely affected by water level fluctuations.