SECONDARY PRODUCTION OF CHIRONOMID COMMUNITIES IN INSECTICIDE-TREATED AND UNTREATED HEADWATER STREAMS

1. Production of chironomid communities of three first order, Appalachian Mountain streams was estimated and the effects of an insecticide-induced disturbance on chironomid production was examined. 2. Annual production of non-Tanypodinae chironomids in the streams during the first study year (no treatment) ranged from 1366 to 3636 mg m-2, while production of Tanypodinae chironomids ranged from 48 to 116 mg m-2. Production/biomass ratios ranged between 19 and 23 for non-Tanypodinae and from 6 to 7 for Tanypodinae chironomids. 3. Insecticide applications resulted in significantly lower chironomid densities and biomass in the treated stream relative to the pretreatment year and reference stream. Annual production of non-Tanypodinae (703 mg m-2) and Tanypodinae (32 mg m-2) chironomids in the treated stream decreased by 64% and 67%, respectively, compared with the pretreatment year. In contrast, production of non-Tanypodinae (2084 mg m-2) increased by 34% and production of Tanypodinae (96 mg m-2) by 57% in the reference stream.