Spatio-Temporal Variations in Water Quality and Pollution Levels of the Great Kwa River Using Benthic Macroinvertebrates

This research assessed spatio-temporal variations in water quality and pollution status of the Great Kwa River by employing benthic macroinvertebrates as bioindicators. Sediment samples were collected using a 320 kg Van Veen grab, sieved through a 0.5 mm mesh, and preserved following established protocols. Retained organisms were identified and analyzed at the Biological Oceanography Laboratory, University of Calabar, while complementary sediment samples underwent heavy metal and nutrient analyses at the Central Analytical Laboratory. Statistical evaluation revealed no significant temporal differences (p > 0.05) in physicochemical parameters or benthic fauna across the sampling months. In contrast, marked spatial differences were observed, with macroinvertebrate abundance and diversity closely linked to variations in nutrient concentrations and heavy metal levels. The absence of pollution-sensitive groups such as Odonata, Trichoptera and Coleoptera indicated moderate ecological stress and pollution. Recorded pH values of 5.5–6.2 reflected slightly acidic to near-neutral conditions, while temperature fluctuations significantly influenced population densities and life-cycle patterns, resulting in shifts in community structure. These findings underscore the effectiveness of benthic macroinvertebrates as sensitive indicators of aquatic ecosystem health and provide evidence of the ecological consequences of anthropogenic pressures on the Great Kwa River. To conserve biodiversity and enhance water quality, the study advocates strict enforcement of waste-management regulations to curb indiscriminate discharge of pollutants such as pesticides, oil residues and solid wastes into river systems. Implementing such measures will help restore ecological balance, facilitate recovery of benthic communities and safeguard the long-term integrity of the riverine ecosystem.