Interactions of Chironomidae and Chaoboridae (Diptera) with Aluminum Sulfate Treated Lake Sediments

Abstract

ABSTRACT Mesotrophic and eutrophic lakes have been treated with aluminum salts (alum) to lower phosphorus concentrations and inhibit phosphorus recycling from the sediment. Changes in the profundal benthic and merobenthic fauna of five selected lakes were assessed, revealing increases in faunal density and diversity in nearly all treated lakes. The dominant organisms were Chaoborus punctipennis (Say) and Chironomus spp. Sediment cores used to evaluate the presence of an aluminum hydroxide floc layer showed aluminum concentrations above extrapolated background levels in most cores within the top 20 cm of substrate. Increased chironomid density resulting from such treatments might reduce the expected benefit from the alum addition. To assess the effect of sediment bioturbation, a bioassay with Chironomus tentans F. larvae was carried out to determine if translocation of phosphorus across the flocculent barrier is dependent on floc thickness or chironomid density. In the absence of a floc layer, chironomid a...