Assessment of water quality parameters and aquatic insects’ assemblages of Lake Alau, Borno State, Nigeria

Abstract

In freshwater environments, aquatic insects have become one of the most trustworthy categories of bioindicators. They are useful tools for biomonitoring because of their ease of collection, comparatively sedentary nature, and variable sensitivity to environmental changes This study assessed the ecological condition of Lake Alau, Borno State, Nigeria, by integrating physicochemical parameters with aquatic insect assemblage data. Statistical monitoring across the three sampling stations revealed that the physicochemical parameters varied spatially, with pH ranging from slightly acidic to neutral (6.7–7.4), dissolved oxygen levels from 4.2 mg/L at the inflow to 6.1 mg/L at the mid-lake, and comparatively elevated nitrate (12–22 mg/L) and phosphate (15–18 mg/L) concentrations. Although the variations in pH and dissolved oxygen were not statistically significant (p > 0.05), the differences in nutrient concentrations (nitrate and phosphate) were significant (p < 0.05), indicating nutrient enrichment and a potential risk of eutrophication. Electrical conductivity (280–400 µS/cm), total dissolved solids (150– 220 mg/L), and sulfate (22–35 mg/L) also showed spatial variation, with higher values at the inflow. A total of 1,246 aquatic insects from seven families were identified, dominated by Chironomidae (37.5%) and Culicidae (13.8%), while Odonata and Hemiptera contributed smaller proportions. Diversity peaked at the mid-lake station (Shannon 2.40; equitability 0.89), reflecting relatively stable conditions. The correlation analysis showed strong positive associations between dissolved oxygen and diversity indices, and strong negative correlations between nutrients and diversity, underscoring the influence of nutrient enrichment on community structure. Lake Alau is moderately impacted by anthropogenic pressures, with nutrient loading and low oxygen posing ecological stress. However, the presence of moderately sensitive taxa suggests resilience and recovery potential. Effective management should integrate routine physicochemical and biological monitoring, reduction of agricultural runoff, improved waste management, and sustainable fisheries regulation to safeguard the lake’s ecological health and socio-economic functions.