Larvae and pupae as indicators of anthropic disturbances: use of traits

Abstract

Urban–industrial contamination in streams affects the functional structure of chironomid assemblages. The aims of this study were to determine whether water quality affects the functional diversity of Chironomidae, and which biological traits are related to water quality variables. We characterized species according to larval and pupal traits and used linear models to test whether functional richness and diversity were related to urban–industrial impact. We performed an RLQ and fourth-corner analysis to evaluate the relationship between traits and environmental variables. Functional richness and diversity were related negatively to nutrients and depth, and positively to temperature, macrophyte cover and dissolved oxygen in the different seasons. Body size, thoracic horn shape and current velocity preferences were significantly related to environmental variables. Our results suggest that nutrients may be an environmental filter for chironomids. The pupal thoracic horn was associated with highly impacted sites, suggesting that oxygen depletion could be an environmental challenge for pupae. Our study shows that urban–industrial impact decreases functional richness and diversity. Furthermore, because some characteristics of the pupae were sensitive to urban–industrial impact, the use of pupal traits is suggested in future biomonitoring analyses of aquatic environments.