Emerging Midges Transport Pesticides from Aquatic to TerrestrialEcosystems: Importance of Compound- and Organism-SpecificParameters

Emerging aquatic insects have the potential to retainaquatic contaminants after metamorphosis, potentially transportingthem into adjacent terrestrial food webs. It is unknown whether thistransfer is also relevant for current-use pesticides. We exposedlarvae of the nonbiting midge,Chironomus riparius, to a sublethalpulse of a mixture of nine moderately polar fungicides andherbicides (logKow2.5-4.7) at threefield relevant treatment levels(1.2-2.5, 17.5-35.0, or 50.0-100.0 mu g/L). We then assessed thepesticide bioaccumulation and bioamplification over the fullaquatic-terrestrial life cycle of both sexes including the egg layingof adult females. By applying sensitive LC-MS/MS analysis tosmall sample volumes (similar to 5 mg, dry weight), we detected allpesticides in larvae from all treatment levels (2.8-1019 ng/g),fiveof the pesticides in the adults from the lowest treatment level and eight in the higher treatment levels (1.5-3615 ng/g). Retention ofthe pesticides through metamorphosis was not predictable based solely on pesticide lipophilicity. Sex-specificdifferences in adultinsect pesticide concentrations were significant forfive 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. Ourresults suggest that a low to moderate daily dietary exposure to these pesticides may be possible for tree swallow nestlings andinsectivorous bats.