Larvae of aquatic Diptera are important predators in fishless wetlands of northeast Alberta. Annual production was estimated for benthic (Chironomidae: Tanypodinae) and pelagic (Chaoboridae: Chaoborus ) dipteran populations in 4 wetlands in surface-mined areas of the Athabasca oil sands, two of which received oil sands mine process material (OSPM; containing polycyclic aromatic hydrocarbons (PAHs)), and two of which were reference wetlands. The structure of benthic and pelagic food webs was estimated by measuring stable carbon and nitrogen isotopes. Stable nitrogen isotopes were also used to determine trophic levels of Tanypodinae and Chaoborus in order to determine their potential to bioaccumulate PAHs. Annual production was estimated along with total PAH body burdens to determine the potential for biomass and PAH export by the emergent adult insects.

Tanypodinae production (1.55-28.77 g/m2 /y) consistently exceeded Chaoborus production (0.009-0.372 g/m 2 /y).

Chaoborus trophic position estimates were consistently greater than estimates for Tanypodinae, suggesting greater PAH bioaccumulation potential for Chaoborus .

Tanypodinae had greater potential to export PAHs (1.86-37.1 mg/m 2 /y) than Chaoborus (1.1 × 10-2 -4.5 × 10-1 mg/m2 /y) due to greater production and PAH body burdens.