The impact of flooding on water quality, zooplankton composition, density and biomass in Lake Iyieke, Cross River-Floodplain, Southeastern Nigeria.

摘要

The physico-chemical parameters, zooplankton composition, density and biomass of Lake Iyieke (Cross River-Floodplain, Nigeria) were studied monthly from February to December 2011 during pre-flood (February-May), flood (June-August) and post-flood (September-December) periods. The study was aimed at evaluating the response of zooplankton to seasonal flooding. Canonical correspondence analysis showed that temperature (28-35 degrees C), PO₄-P (0.10-0.16 micro g/L), pH (6.50-6.80), transparency (0.17-0.98 m), conductivity (18.0-56.00 micro S/cm) and total dissolved solids (8.50-28.00 mg/L) were the main environmental variables that influenced zooplankton dynamics. Rotifers of the families Collothecidae, Collurellidae and the cladoceran Scapholeberi kingi were recorded in the lake for the first time. Rotifers were dominant in the pre-flood period, while microcrustaceans were dominant in the flood and post-flood periods. Contrary to our expectations, species richness (56 species) and density (527 ind/L) peaked during the pre-flood and flood periods, respectively. Based on our results and previous studies on the lake, we recommend undertaking a comprehensive study on this and other lakes within the Cross River basin in order to gain a clear understanding of the impact anthropogenic activities (dams and dredging) and climatic factors (that could alter the intensity and duration of flood) could have on zooplankton.