Secondary Production, Emergence, and Export of Aquatic Insects of a Sonoran Desert Stream

Abstract

Aquatic insect secondary production, emergence, and export of adults to the adjacent terrestrial ecosystem were assessed in Sycamore Creek, Arizona, by means of benthic sampling, emergence traps, and catch—nets that passively sampled adults falling into the stream. Annual secondary production was 120.9 ± 18.0 g°m — 2 °yr — 1 an emergence was 23.1 g°m6 — 2 °yr — 1 (in dry mass units). The ratio of annual emergence to annual production (E/P) varied among taxa and ranged from 2 to 29%. Chironomids comprised 48.2% of production and 59.7% of emergence and mayflies accounted for 45.9 and 19.2%, respectively. Approximately 3% of emergent insect biomass returned to the stream; thus 22.4 g°m — 2 °yr — 1 was transferred to the adjacent terrestrial ecosystem. The transfer of a significant portion of aquatic insect biomass to the terrestrial habitat reduced insects available to stream insectivores while providing prey for insectivores in neighboring terrestrial ecosystems.