Macroinvertebrate communities and physicochemical characteristics along an anthropogenic stress gradient in a southern Nigeria stream: Implications for ecological restoration

Abstract

Anthropogenic pollution of water has become an urgent management challenge across the world. We explored benthic macroinvertebrates community structure in relation to physicochemical conditions of the water column and sediments along an anthropogenic stress gradient in a southern Nigeria stream. We used Principal Component Analysis (PCA) followed by Canonical Corresponding Analysis (CCA) to analyse the original monitoring dataset (33 water quality indexes), identify the important physicochemical variables, and evaluate the relationship between the concluded important physicochemical variables and macroinvertebrates assemblages. PCA and CCA showed that sediment heavy metals explained larger part of variance in benthic macroinvertebrates assemblage. CCA showed a strong relationship between species metrics and environmental predictors. Sediment heavy metals pollution residues from industries that have relocated from the catchments of Site 2 affected the sediment and water quality as well as the benthic community structure at this site, demonstrated by the dominance of organic and heavy metal pollution tolerant taxa. Due to rapid urbanization, gradients of anthropogenic impacts resulted in an increase in the profile of heavy metal and nutrient concentrations along Sites 2, 3, and 4, indicated by the dominance of pollution-tolerant taxa of Oligochaete and Diptera groups. Our results supply useful baseline knowledge on urban chemical pollution in a developing world perspective. The long-term impression from sediment heavy metals pollution residues resulting from relocated industries should be a concern to environmental managers. For ecological restoration, objective management policies, legislation, and participatory scientific monitoring are key.