Benthic Macro-invertebrate Community Diversity of Orhuwhorun River in Udu Wetlands.

Benthic macro-invertebrate studies were done on Orhuwhorun River in Udu wetlands in Delta State, Southern Nigeria from March to December, 2011 in three selected stations. Sampling was done using a hand modified Eckman grab for sand and silt, the kick sampling technique and floatation method. They were sorted and identified using identification keys. A total of 2466 individuals were recorded in 66 taxa species belonging to thirteen (13) groups. Crustacean was the dominant group (36.29%) closely followed by gastropoda (35.60%) and diptera (21.04%). Significant similarity in fauna composition was observed. Station 3 had the highest population density with a relative abundance of 58.19% followed by station 2 (32.03%) and station 1 (9.77%). Diptera had the highest species diversity while nematode and lepidoptera had the least amongst the groups. Station 1 had the highest species richness (d) followed by station 3 and least in station 2. Species diversity showed no significant difference between the stations. Values for pollution tolerance index ranged between 13 and 15 at the stations. The highest value for pollution tolerance (PTI) was recorded in station 2 and the least in station 1. Positive significant correlations existed between most benthic organisms. The water quality is described as “fair”.