Environmental conditions and plankton of the Omu Creek, Lagos, Nigeria
Phytoplankton, zooplankton and water quality characteristics in Omu creek were investigated (October 2012 – February 2013). Air and water temperatures (⁰C) (30.34), transparency (cm) (23.43), conductivity (μS/cm) (2728.12) and salinity (0/00) (1.37) recorded higher values in the dry period while acidity (mg/L) (8.48), alkalinity (mg/L) (8.48) and total hardness (mg/L) (349.10) recorded reduced values. The phytoplankton diversity consisted of diatoms and blue-green algae. A total of 8 species from 5 genera were observed. Diatoms were more diverse with 7 species from 4 genera. The blue-green algae recorded one species. Diatoms accounted for 98% (centric – 86.7% and pennate diatoms –13.3%) of the total phytoplankton. Zooplankton diversity consisted of adult copepods, rotifers and juveniles stages from 10 species and 10 genera were recorded. Crustaceans were made up of 7 species from 7 genera. Rotifers recorded 3 species from 3 genera and the juveniles, 3 larva stages. Juvenile stages accounted for 51.85% (gastropod larva – 60.7%, copepod nauplii – 25% and rotiferan egg – 14.3%). Diatoms and juveniles stages were more frequently occurring and both increased in terms of number in the dry period, notably January. Low plankton species diversity is possibly linked to the effect of pollution and dilution from inflowing lagoonal water associated with rainfall.
Keywords: Water quality, phytoplankton, zooplankton, diatoms, copepod, Epe Lagoon