Assessment of some physical, chemical and biological parameters of Lake Dangana, Niger State, Nigeria

Ecological systems change over time due to anthropogenic and natural activities, regular monitoring is therefore necessary for identifying malignant changes and conservation of biodiversity. This study was undertaken to ascertain the health and biological diversity of Lake Dangana using both biotic and abiotic indicators. Samples for physico-chemical and biological analyses were collected monthly from four sampling stations in Lake Dangana from January to August, 2020 using standard methods. The results of physico-chemical variables were: temperature (23.5-26.5ºC), dissolved oxygen (3.96-4.13mg/l), biochemical oxygen demand (3.00-.12mg/l), pH (6.88-7.11), conductivity (86.43-94.80µS/cm), nitrate (0.67-0.76mg/l) and phosphate (0.85-1.04mg/l). Conductivity, nitrate and phosphate varied significantly (p<0.05) between stations. A total of 318 individuals from 13 species and 10 families of macroinvertebrates were encountered during the study period. Hemiptera (35.52%), Coleopterans (34.59%), Odonata (22.95%), Dipterans (5.03%) and Oligochaetes (1.87%) were the dominant groups. The first two Canonical Correspondence Analysis (CCA) axes explained 87.33% of macroinvertebrate-environment relationship and pH (-0.99), BOD5 (-0.62), nitrate (-0.61), conductivity (-0.59) and phosphate (-0.57) were the dominant structuring factors. Six bacteria species; Bacillus sp, Escherichia coli, Micrococcus sp., Staphylococcus aureus, Klebsiella sp and Pseudomonas sp. and five fungi species; Aspergillus fumigatus, A. niger, A. flavus, Penicillium sp and Mucor sp. were encountered. The presence of some of these microorganisms such as E. coli in the lake is an indication of faecal contamination and this could endanger public health.