Zooplankton Fauna of a Creek Receiving Petroleum Refinery Effluent in South-South Nigeria

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The zooplankton community structure of Ekerekana/Okari Creek in Okrika, South-South Nigeria had been studied for two months, February and August 2014 representing wet and dry months. Surface water for physico-chemical and zooplankton samples, were collected in 4 stations for analysis, identification and enumeration. Seasonal mean parameter values varied within February and August temperature, 28.5oC ± 1.5 and 30.7oC ± 3.42; flow rate was 8cm/s ± 4.1 and 8.7cm/s ± 4.3; depth 120cm ±30.7 and 200cm ± 20.9; pH 7.9 ± 0.14, 7.0 ± 0.04; salinity was 23.6% ± 1.6, 21.4 0/00 ± 0.2; DO was 9.3mg/l ± 2.8, 2.3mg/l ± 1.04, BOD was 6.9mg/l ± 4.2, 0.8mg/l ± 0.1 respectively. Four zooplankton taxa (Protozoa, Rotifera, Cladocera, and Copepoda) found during the study showed seasonal variations between dry and wet months respectively, with a total of 72 organisms in February and 121 organisms in August respectively. Dominant taxon in the dry month was Protozoa with 32 organisms representing 44.4% of total organisms. However, Copepoda with 41 organisms, representing 33.9% of wet month organisms dominated August samples.