Assessment of the Impact of Anthropogenic Activities on Physicochemical Parameters and Phytoplankton Compositions of Kalgo River, Kebbi State

Abstract

Anthropogenic activities can have significant and often detrimental effects on aquatic ecosystems, including water quality, biodiversity, and the overall ecosystem. This study aimed to assess the impact of washing, fishing, and agricultural activities on physiochemical parameters and phytoplankton composition in the Kalgo River. Water samples were collected from stations A (farming and irrigation), B (fishing activities), and C (washing site) using plankton nets and one-liter plastic bottles following standard methods. Phytoplankton species were identified through comparative morphological examination using a binocular light microscope (Olympus BH2) at a magnification of 100x after centrifuging the water samples. In August, higher values of pH (7.90±0.23), EC (793.91±3.56 µs/cm), P (0.31±0.05 mg/l), NH4 (0.63±0.23 mg/l), and TDS (529.27±0.13) were recorded. The highest temperature (29.66±1.50°C) and maximum concentrations of DO (7.52±0.25 mg/l), BOD (22.4±10.29 mg/l), Ca2+ (164.0±13.21 mg/l), and Cl- (15.40±0.59 mg/l) were found in June. A total of 341 phytoplankton species distributed across 37 genera and belonging to seven classes were identified. The dominant class was Chlorophyceae (31.43%), followed by Bacillariophyceae (25.72%) and Cyanophyceae (20.00%), with Rhodophyceae recording the lowest percentage (2.86%). Station B exhibited the highest species composition (41.35%), while station C had the lowest (26.96%). No significant difference (P>0.05) was observed in phytoplankton composition variations between the stations. Crucigenia sp. had the highest occurrence (8.50%), followed by Navicula digitoradiata (7.33%), Volvox sp. (6.16%), and Craticula sp. (5.28%). Asterionella sp., Vaucheria sp., and Melosira variants each accounted for 0.88% of the composition. Despite the diverse phytoplankton assemblage in the Kalgo River, further studies are necessary to evaluate the specific impacts of anthropogenic activities on different phytoplankton species and their overall health in the river.