Physico-Chemical Factors Influencing Zooplankton Community Structure of a Tropical River, Niger Delta, Nigeria

Abstract

The Physical and chemical factors influencing the abundance, diversity and species richness of zooplankton in Mbo River, Akwa Ibom State, Nigeria were studied for twelve months (December, 2009- November, 2010) using standard analytical methods. The aim was to study the environmental factors determining zooplankton structure as reference point for the sustainable management of the river in view of the proposed development plans for the river basin. The result showed that Crustacea was highest and constituted 48% in Station I, and 30.8% and 33.3% in Stations II and III respectively. Other taxanomic groups present in this study include Rotifera which contributed to 20.0%, 50.0% and 55.6% in Stations I, II and III, respectively. Mollusc in Station I contributed to 8.0% of the species composition in this Station but was absent in Stations II and III. Protozoa which contributed to 9.1% of the total zooplankton composition in Station I was not recorded in the other two stations. The maximum diversity (Shannon-Weiner Index) per station/month (2.79) was calculated in Station I in September, 2010 and the minimum per station/month (0.93) was observed in Station III in July. Seasonally, the wet season recorded the maximum Shannon-Weiner Index value of 3.02 while the dry season recorded lower values. The significant seasonal variation in zooplankton density (cells/l), diversity and richness was regulated by rainfall, which also modulated the impact of the physico-chemical variables of the river surface water.

Keywords: Community structure, Nigeria, Niger Delta, Physico-chemical factors,  Zooplankton