Ecological risk assessment of the hydrochemistry for benthic macroinvertebrates adjoining Chanomi Creek, Niger Delta, Nigeria

Water pollution and unregulated human activities pose global risks to benthic macroinvertebrates (BMIs) and their ecological roles. This study provides a novel ecological risk assessment of hydrochemical contamination in Chanomi Creek, Niger Delta, by integrating heavy metal (HM) pollution indices with BMI biomonitoring, offering new insights into the spatiotemporal dynamics of aquatic ecosystem degradation. Water and benthic samples were collected monthly from 10 stations (March 2020–August 2021) using a Hydrobios water sampler and Van-Veen Grab. Conductivity, total suspended solids (TSS), dissolved oxygen (DO), total dissolved solids (TDS), sulphate, turbidity, and HMs exceeded regulatory limits. Biological oxygen demand and DO were elevated in the wet season, while TDS, conductivity, and turbidity increased in the dry season. Waste disposal, illegal refining, and crude oil extraction intensified turbidity and chemical pollution, especially in the dry season. Heavy Metal Pollution Index (2564.44–4693.33) and Evaluation Index (113.2–289.6) revealed extreme contamination, mainly from Cu and Cr, especially in the dry season. PCA identified turbid and excessive solids-dominated PC1 (32.46 % variance), while PC2 (16.86 %) reflected nutrient and HMs contamination. Molluscs (77.5 %), mainly Tympanotonus fuscatus (32.5 %), dominated the benthic community, exhibiting resilience to moderate pollution but vulnerability to severe contamination. nMDS and CCA linked BMI distribution to water quality, with high metal loads reducing diversity. Mytilus edulius, Cassostrea gazar, and Arenicola marina indicated poor water quality, while Tf var.radula, Pachymelania aurita, and T. fuscatus indicated disturbed but biologically functional ecosystems. These findings support regulatory frameworks, ecosystem conservation, and sustainable water resource management.