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Nutrient limitation was investigated in the Manyame lakes, namely, Harava Dam, Seke Dam, Lake Chivero, Lake Manyame and Bhiri Dam, during 2004-05. Selenestrum capricornutum was used as the test organism in one group of bioassays and the lakes' natural phytoplankton population in the other. Nitrogen was indicated to be the primary limiting nutrient in Harava Dam, Seke Dam and Lake Manyame. Phosphorus was found to be the primary limiting nutrient in Bhiri Dam while no nutrient was indicated to be limiting the growth of phytoplankton in Lake Chivero; instead, light was implicated to be limiting the growth of phytoplankton. Harava Dam and Seke Dam showed signs of enrichment, relative to 1977, attributed to sewage discharge from expanding urban settlements in Ruwa and surrounding areas. Lake Chivero has remained much the same in the last 30 years and was indicated to be acting as a nutrient trap, since the dams downstream of it were not found to be as eutrophic. Lake Manyame, Seke Dam and Harava Dam were concluded to be mesotrophic, Bhiri Dam oligotrophic and Lake Chivero eutrophic.

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Sediments act as a sink, being an integrator and an amplifier for metals in rivers, lakes and reservoirs. Thus, sediment quality has been recognized as an important indicator of aquatic pollution. The concentrations of aluminium (Al), calcium (Ca), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn) and sodium (Na) were studied in the surface sediments of Lake Chivero, Zimbabwe, to determine metal accumulation, distribution, pollution status and to distinguish natural background metal levels from human pollution sources. Sediment samples were collected from 17 locations during a two‐year (2014–2015) monitoring period during the hot–dry, hot–wet and cool–dry seasons. The overall mean metal concentrations exhibited the following decreasing order: Fe > Al>Mn > Ca>K > Mg>Na. The Mn levels for all sites and seasons were above the severe effect level (SEL). The highest metal and enrichment factor (EF) values were observed for the hot–wet season, indicating the period when the reservoir received the highest metal pollution from its catchment. The Geochemical index (Igeo) values for Mn for all seasons indicated moderately to strong contamination in sediments. The pollution load index (PLI) for all seasons indicated low pollution levels. Sediment contamination was attributed to natural sources for Al, Na and K and anthropogenic sources for Fe, Ca, Mg and Mn. The levels of studied metals in the Lake Chivero sediments are comparable to other eutrophic lentic systems. The results of the present study provide baseline information necessary for developing future metal pollution control strategies for Lake Chivero and its catchment.