ABSTRACT

This study investigated the diversity of benthic macro invertebrates in the marine waters offshore Forcados river, Niger delta, Nigeria. To determine the species composition and relative abundance of the benthic macro fauna of Forcados river. Sampling was carried out between 4^th-8^th September 2020, a van veen grab was used to collect samples from the sediment and was sieved using a 0.1mm mesh size sieve, A hand lens was used in identifying this organisms and placed them accordingly into a specimen bottle and carefully preserved with 10% formalin. Three groups were recorded and dominated by Mollusc (82%), Polychaete (9.30%) and Crustaceans (7.44%). A total of 215 individuals were recorded in the study area constituting over 24 taxa, belonging to 3 phylum, 5 classes, 14 order and 22 families from all the groups recorded. molluscs was the highest with 11 species, followed by 8 species  from polychaete, crustaceans recorded the lowest with 5 species. From all the individuals species identified Turritella communis was recorded as most abundant species with 73 individuals in the mollusc groups. The margelef index and Shannon index was used in calculating for the species diversity, taxa richness and evenness. The presence of the polychaete species Capittela capitata which is an opportunistic species tolerant of stressful conditions and is of great interest in bio-monitoring of marine environment, and is often found in polluted waters (sewer discharge, hydrocarbons and metals) where it out competes less tolerant species. The low diversity of the taxa from the study area can be attributed to the short duration of sampling and can also be due to possible effect of anthropogenic activities in this study area. It is therefore recommended that further detailed long term study should be carried out in this study area for a more comprehensive understanding of the abundance and diversity of the macro invertebrates in the area.