Zooplankton communities of the river Ossiomo, Ologbo, Niger delta, Nigeria

Abstract

Zooplankton communities of the River Ossiomo at Ologbo, Niger Delta, Nigeria were investigated from April 2012 to December 2012. Three stations were studied from upstream to downstream with a distance of about 2 kilometres between each station. A total of 42 taxa were identified; 11 species of cladocerans, 6 copepods and 5 rotifers in the following order of dominance: copepoda > cladocera > rotifera. A total zooplankton population of 1330 individuals was recorded during the study period. Copepods and cladocera represented the predominant species (51.1% and 43.6% of the total zooplankton community respectively) followed by rofiters (5.3%). Copepods and cladocerans were dominated by both cyclopoid (51.1%) and chydorids (27.8%), respectively. The dominant copepod and cladocera species were Thermocyclops neglectus and Alona eximia representing 33.1% and 15.8% of the total zooplankton, respectively. The calculated diversity indices indicated that station 1 was more diverse followed by station 3, while zooplankton species in station 2 were least diverse. Community composition was similar at both stations 2 and 3, but varies seasonally across the three stations. Higher species number and density was found during the wet season with a trend of declining proportion towards the dry months.

Keywords: Zooplankton, Species, Population, Diversity, Abundance, River Ossiomo