CHARACTERIZATION OF THE ZOOPLANKTON COMMUNITY STRUCTURE OF POLLUTED ERUVBI STREAM, BENIN CITY, NIGERIA

Abstract

The zooplankton community of a polluted section of Eruvbi stream was analyzed emphasizing composition and
abundance of organisms. Samples were collected monthly between March and August, 2009 from three stations in
the system: upstream, discharge point, and downstream. Margalef’s species richness index (D), Shannon-Weiner
index of general diversity (H’) and Evenness index (E) measures of diversity were used to describe the zooplankton
community. Forty species made up of nine species of cladocerans, nine species of copepods and their developing
stages and 22 species of rotifers were encountered during the study period with rotifers being the dominant taxa at
all stations. The species richness of the zooplankton communities, at the polluted station 2 (discharge point) was
however less than what obtained at the upstream and downstream stations. The most frequent zooplankton species
in the polluted part of the stream were the rotifers Brachionus calyciflorus, Brachionus falcatus, Brachionus
caudatus, and Testudinella patina. Regarding relative abundance, there was a common trend where rotifers were
dominant in the three sampling stations, followed by copepods and cladocerans. All of these zooplankton groups
showed lowest abundance in station 2 (discharge point).