Emerging Midges Transport Pesticides from Aquatic to Terrestrial Ecosystems: Importance of Compound- and Organism-Specific Parameters.

Abstract

Emerging aquatic insects have the potential to retain aquatic contaminants after metamorphosis, potentially transporting them into adjacent terrestrial food webs. It is unknown whether this transfer is also relevant for current-use pesticides. We exposed larvae of the nonbiting midge, Chironomus riparius, to a sublethal pulse of a mixture of nine moderately polar fungicides and herbicides (logKow 2.5-4.7) at three field relevant treatment levels (1.2-2.5, 17.5-35.0, or 50.0-100.0 μg/L). We then assessed the pesticide bioaccumulation and bioamplification over the full aquatic-terrestrial life cycle of both sexes including the egg laying of adult females. By applying sensitive LC-MS/MS analysis to small sample volumes (∼5 mg, dry weight), we detected all pesticides in larvae from all treatment levels (2.8-1019 ng/g), five of the pesticides in the adults from the lowest treatment level and eight in the higher treatment levels (1.5-3615 ng/g). Retention of the pesticides through metamorphosis was not predictable based solely on pesticide lipophilicity. Sex-specific differences in adult insect pesticide concentrations were significant for five of the pesticides, with greater concentrations in females for four of them. Over the duration of the adults' lifespan, pesticide concentrations generally decreased in females while persisting in males. Our results suggest that a low to moderate daily dietary exposure to these pesticides may be possible for tree swallow nestlings and insectivorous bats.