AQUATIC INSECTS’ COMMUNITY STRUCTURE

ABSTRACT

Benthic aquatic insects receive the most direct impact when surface waters are perturbed. The community structure and seasonal variation of the aquatic insects in relation to physio- chemical parameters in Amagba-Oko oroma River, Benin City were studied during the dry and rainy seasons of 2023 in three designated stations. Aquatic insects’ samples were collected using D-frame net and water parameters were measured according to standard procedure. The samples collected were also sorted and identified till the lowest taxa possible. Physicochemical parameters such as air temperature, transparency and depth were significantly affected by stations’ land-use activities (p > 0.05) in the period sampled, while turbidity, pH, chromium, copper and zinc exceeded the stipulated guideline. A total of 807 individual aquatic insects were collected represented by 14 families and 6 orders including Diptera, Odonta, Coleoptera. Dipteran was the most dominant insect order and Chironomus sp the most dominant taxon in the study area. Site 2 has the richest and best taxa distribution, while site 3 has the poorest least in taxa distribution. In terms of seasonal variation, on the average, higher abundances of macroinvertebrates were recorded during the dry season than in the rainy season. Correlation matrix revealed strong relationship between the major environmental drivers and aquatic insects. Ablabesmyia sp. was positively correlated with electrical conductivity; Chironomus sp. had a positive relationship with sulphate and chloride; Hydrovatus sp. was positively correlated with electrical conductivity and total dissolved solids. Overall, this study provides further insights and understanding regarding land-use impacts on the ecological health of the Amagba-Oko Oroma River, and we recommend more stringent regulations to control human pressure on the river systems within the studied area to enable surface waters in the area to sustain the provision of desired and valued ecosystem services.