COS 8-8
Analyzing the influence of environmental variables on zooplankton composition of a near coastal river, delta region, Nigeria, using canonical correspondence analysis (CCA)
This tropical river drains into the Cross River Estuary at Ibaka in the Bight of Bonny, with which it maintains a permanent mouth thus exposing the river system to tidal ebb and flow. The delta region of Nigeria in which the river is located is very rich in petroleum hydrocarbon with increasing oil activities and other anthropogenic perturbations. The influence of environmental variables on zooplankton composition of Mbo River was investigated for one year (November, 2009 - October, 2010) to evaluate the interaction of physical and chemical parameters, different locations and zooplankton species composition and distribution in relation to the anthropogenic perturbation and major seasonal rainfall patterns. Standard analytical procedures for both physico-chemical attributes and zooplankton were employed and the dataset generated was analyzed using Canonical Correspondence Analysis (CCA).
Results/Conclusions
The physical and chemical attributes of the river varied remarkably with significant (p<0.002) spatial differences. Each of the species exhibited distinct inclinations toward specific environmental attributes with spatio-temporal tendencies. The study showed that several environmental parameters had a close relationship with the species matrix and species such as Macrosetella rosea, Oithonia Setigera, Arcella vulgaris and Nauplii copepod have their highest abundances where levels of nitrate-nitrogen and sulphate are at their highest recorded levels. From the study also, increase in levels of dissolved oxygen results in an increase in the relative abundances of species such as Dicranophorus sp, Upogebia sp, Cyclops sp, Cyclidium sp, and Paracalanus parvus. Majority of the water quality attributes of Mbo River were significantly influenced by precipitation and anthropogenic perturbations. CCA has, therefore, proved significantly that the composition and distribution of prevalent biota in this tropical river is affected by the prevailing spatio-temporal environmental factors.