Assessing the Effects of Petroleum Spills on Benthic Macroinvertebrate Communities in Ogoni Rivers, Rivers State

Decades of oil exploration and production activities in Ogoni land have resulted in recurrent petroleum spills that degrade freshwater habitats and affect aquatic biodiversity. This study assessed the effects of petroleum contamination on benthic macroinvertebrate communities in three rivers in Ogoni land, Rivers State, comparing spill-affected reaches with uncontaminated reference sites. Macroinvertebrates were sampled using a standard kick net technique across three seasons. Collected organisms were identified to family level and used to calculate biotic integrity indices, including the Hilsenhoff Biotic Index and Shannon Diversity Index. Physicochemical parameters including total petroleum hydrocarbons, dissolved oxygen, and turbidity were simultaneously measured. Results showed significantly lower macroinvertebrate diversity and abundance at petroleum-contaminated sites, with communities dominated by pollution-tolerant oligochaetes and chironomid larvae. Reference sites supported greater taxonomic richness, including sensitive Ephemeroptera, Plecoptera, and Trichoptera taxa entirely absent from contaminated reaches. Strong negative correlations were found between total petroleum hydrocarbon concentrations and both diversity indices. These findings confirm that oil spills cause measurable and prolonged damage to river benthic communities in the Niger Delta. The study recommends incorporating macroinvertebrate bioassessment into routine environmental monitoring for oil spill impact evaluation in the region. Keywords: benthic macroinvertebrates, petroleum spills, Ogoni land, freshwater ecology, bioassessment.