Anthropogenic impacts influence the functional traits of Chironomidae (Diptera) assemblages in a neotropical savanna river basin

Increased demands for water affect its quality and availability and threaten biodiversity. In freshwaters, the Chironomidae (Diptera) represents ~ 50% of macroinvertebrate individuals and have great potential to improve ecological assessment tools. Incorporating trait-based approaches in those tools can further improve how we assess the effects of human disturbances on aquatic macroinvertebrate assemblages. Given that chironomid genera have different degrees of sensitivity to anthropogenic disturbances, we expected that composition, structure and functional characteristics of chironomid genera would be negatively affected by anthropogenic disturbances in a neotropical savanna river basin. We used nine traits in 32 categories related to Chironomidae functional roles. Out of 6147 individuals distributed in three subfamilies, we identified 52 chironomid genera collected from 30 randomly selected stream sites. The index of functional divergence was lower in places with greater anthropogenic disturbance of riparian vegetation. A RLQ matrix analysis revealed a significant relationship between genera abundance and environmental variables as well as with biological traits. We observed a positive relationship between Tanypodinae, which are mainly engulfer predators, with average embeddedness, % sand and catchment pasture. Three Chironomidae genera (Stenochironomus, Endotribelos and Beardius) were positively related to miner habit, herbivore feeding strategy and larger body size. We found that physical habitat structure and food resources were the most important factors structuring Chironomidae assemblages in the study sites and that chironomid genera were effective for assessing basin ecological status.