Benthic Macro-Fauna Composition and Abundance in Sombreiro River, Niger Delta, Nigeria

The benthic macro-fauna composition and abundance in sombreiro was studied for a period of two years (August 2007 - July2009). A total of twenty-eight species belonging to fourteen (14) families, six (6) classes and three (3) phyla were recorded in Sombreiro River. The phylum Annelida dominated with two classes (Oligochaeta and Polychaeta). Oligochaeta was represented by two families (Naididae and Lumbricidae) and seven species having 25% by composition. Polychaeta was represented by seven families (Nereidae, Nepthyidae, Capitellidae, Eucinidae, Glyceridae, Arenicolidae and Syllidae) and thirteen species having 46.4% by composition. The Phylum arthropoda was represented by two classes (Crustacea and inseita). Two families (Gammaridae and Penaidae) having two species consisting of 7.2% were recorded, for the class crustacea. The class insecta was represented by one family (Chironomidae) with one species consisting of 3.6%. The phylum Mollusca was represented by two classes (Gastropoda and Bivalvia). Gastropoda had two species with 7.2% composition and Bivalvia has three species with10.7% composition. Oligochaeta was the highest and constituted 62.0%. The others were Polychaeta (23.9%), Insecta (6.7%), Gastropoda (3.9%), Bivalvia (2.2%) and Crustacea (1.3%). The mean diversity(S) ranged between 11 species. Mean abundance of individuals (N) was 985. Mean Margalef index (d) value was 1.339. The mean value for Shannon-Wienner (H) was 0.956. Mean Pielou’s index of relative density or evenness index (E) was 0.986. Mean SimpsIn’s Dominance index (C) was 0.623.