Relative lake level fluctuations and their influence on productivity and resilience in tropical lakes and reservoirs

Plankton and Macroinvertebrate Community Composition in the Pelagic and Non-Vegetated Littoral Drawdown Zones of a Shallow Reservoir, Manjirenji, Zimbabwe

“…The Dam, a relatively shallow reservoir located in the located in the arid south eastern part of Zimbabwe is subject to wide water level fluctuations reaching a drastic 12.6% or 4.66 metres from an average of 24. 2 metres in November 2012, 18.9% in September 2013 and increasing to just below 40% in January 2014 (ZINWA, 2014). Though the main purpose for its construction was to supply irrigation water for the vast sugar cane producing Mkwasine Estates, other multiple designated uses comprising of domestic water abstraction, lakeshore irrigation, downstream wheat irrigation and small scheme hydroelectric power generation have subsequently evolved (Svubure et al, 2010;ZINWA, 2014).…”

“…High R values (.> 0.60) in the pelagic zone indicate a strong relationship among the Secchi depth, TN, TP and chlorophyll a in the pelagic zone ( Table 2). Multiple regression indicates no significant predictor factor (p < 0.05) among Secchi depth, TN, TP towards chlorophyll a production in both littoral and pelagic zones in 18 Species richness of zooplankton was 14±2 (mean ± standard deviation) and 11±2 for the littoral and pelagic zones respectively (Appendix F). The abundance of zooplankton followed a distinct pattern over the sampling period which consisted of Rotifer > Copepod > Cladocera for both littoral and pelagic sites.…”

“…Though the effects of natural water level fluctuations on water quality and aquatic organisms are magnified if the dams have other non-seasonal water withdrawing activities present (Abrahams, 2008). Water level fluctuations serve to promote high species diversity in littoral zones of shallow lakes and for doubling the productivity of these lakes thus projecting fish densities in water bodies (Antenucci et al, 2003;Kolding and van Zwieten, 2012).…”

“…In shallow turbid lakes, spatial isolation, stochastic nutrient stoichiometry and water level fluctuations due to the constant shifting of the ecotone up and down the shoreline affects aquatic biodiversity (Wang et al, 2011;Kolding and van Zwieten, 2012). For this exploratory study, we examined the effects of physicochemical variables on the community composition of phytoplankton, zooplankton and macroinvertebrates in different zones of a shallow lake, Manjirenji in Zimbabwe, which is prone to extreme water level fluctuations.…”

“…Although most research on plankton and macroinvertebrates has focused on river reservoirs (transition from river to lake/reservoir) (Grzybkowska et al, 1990), other reservoir studies have been limited to pre-and post-impoundment surveys or have been done on systems that have irregular drawdown patterns or low winter water levels that subject the benthos to freezing (Kolding and van Zwieten, 2012). Few, or sparse studies have been conducted in shallow lakes with non-vegetated shorelines to explore the effect of stochasticity of nutrient stoichiometry on plankton and macroinvertebrates assemblages (Baldwin et al, 2008).…”