Limnological Characteristics, Phytoplankton Assemblage and Environmental Assessment of Hadejia River, North-Western Nigeria: A Comprehensive Survey

Abstract

Study’s Excerpt/Novelty This study is the first of its kind that offers a comprehensive analysis of phytoplankton dynamics in the Hadejia River, highlighting significant spatial and temporal variations in relation to key limnological variables. It uniquely identifies the influence of environmental factors on specific phytoplankton species and provides baseline data for future ecological monitoring. The research showcases the impact of anthropogenic activities on water quality, particularly at Station B, contributing critical insights into the river's ecological health and informing conservation strategies. Full Abstract This study assesses variations in phytoplankton abundance, composition, and distribution in the Hadejia River in relation to key limnological characteristics across both spatial and temporal dimensions. Over six months in 2018, water samples were collected from the river and analyzed for environmental variables alongside the quantification and identification of phytoplankton using standard protocols. pH and temperature measurements were conducted in situ. Results indicated significant variations (P < 0.05) in pH, temperature, turbidity, nitrate, and phosphate levels across different months, although no significant differences were observed between sampling stations. The highest nitrate value (5.41 mg/L) and phosphate levels (6.55 mg/L) were recorded in August at Station B (STB). 693 Phytoplankton individuals from five divisions were identified, with peak abundance, composition, and distribution observed during the dry season. Key species such as Selenastrum bibraianum, Tetraedron regulare, Tabellaria flocculosa, Gomphosphaeria lacustris, Microcystis aeruginosa, Rhabdoderma lineare and Tabellaria fenestrate were consistently present throughout the study period. Shannon_H diversity index values for Cyanophyta, Pyrrophyta, and Euglenophyta ranged between 1.34-2.02, while Bacillariophyta and Cyanophyta exhibited reduced diversity (1-1.32) and species richness (0.55-0.68) at STB. Canonical correspondence analysis revealed that the selected environmental variables strongly influenced phytoplankton abundance and diversity, with the exception noted for Microcystis aeruginosa, Gomphosphaeria lacustris, Rhabdoderma lineare, and Chlamydomonas ehrenbergii. These results suggest deterioration in water quality, particularly at STB, possibly due to anthropogenic activities. Furthermore, this study provides valuable baseline data for future research endeavors aimed at monitoring and managing the ecological health of River Hadejia