Chironomids as bioindicators of heavy-metal contamination

Freshwater invertebrates play an important role in the ecological maintenance of aquatic ecosystem services, mainly in secondary production and energy flow dynamics. Among those invertebrates, larval chironomids (Chironomidae) serve as bioindicators of contaminant stress. Due to their feeding mechanisms, chironomids live in close contact with the sediments which serve as a pollution sink to which the most persistent chemicals are bound. Consequently, the larval species composition is strongly susceptible to heavy metals and oil contamination, and organic pollution1,2. Certain concentrations of heavy metals in riverbed sediments display biological long-term effects that cause characteristic mouthpart deformities in larval chironomid species2,3. Thus, comparative biological surveys of the species composition and mouthpart morphology of larval chironomids can depict longer-term exposures of benthic communities to both lethal and non-lethal concentrations of heavy metals and other contaminants.