Temporal and spatial variability in macroinvertebrate community structure in relation to environmental variables in Ajijiguan Creek, Niger Delta, Nigeria

Abstract

Variations in macrobenthic community structure in time and space along a pollution gradient were examined in a small Niger Delta creek in 2006–2007. Salinity fluctuated between fresh and mesohaline conditions with values ranging from 0.4 to 5.2, and conductivity ranged from 16.9 to 36.0 μS cm^–1. The upper creek was relatively free of gross pollution, with high dissolved oxygen and low nutrient and salinity levels. At its lower end, BOD₅ was relatively high and nutrient levels were high, indicating substantial organic input. The middle and upper creek were dominated by Naboandelus africanus, Appasus sp., Laccotrephes sp., Plea sp. (Hemiptera) and Georissus sp. (Coleoptera). Sensitive taxa such as Neoperla sp. (Plecoptera), Ecnomus sp. (Trichoptera) and Ephoron sp. (Ephemeroptera) were restricted to the upper creek. At the impaired site Neritina sp. (Mollusca), Sesarma sp. (Decapoda), Nereis sp. (Polychaeta) and Chironomus sp. (Diptera) dominated the assemblage. Canonical correspondence analysis indicated that dissolved oxygen, conductivity, total nitrogen, BOD and temperature structured the invertebrate assemblages. Overall, human activities and land-use practices around the creek resulted in varying degrees of habitat degradation and nutrient enrichment, reflected by the macroinvertebrate assemblages which can be used effectively to monitor the effect of such activities on Niger Delta creeks.