Benthic Macroinvertebrates in the Big Eau Pleine, a Fluctuating, Central Wisconsin Reservoir

[摘要] Benthic macroinvertebrate distribution, abundance,and composition were observed in a fluctuating {7.7 m)central Wisconsin reservoir during 1973-1974. Chironomidaeand Oligochaeta represented 98 percent of the totalfauna by number. The chironomid, Chironomus plumosus,and oligochaete, Limnodrilus sp., each averaged 36 percentof the total benthic biomass. Annual mean numbers andbiomass in areas exposed to atmosphere, exposed to icecover, or remaining inundated were 3025/m^2 (1.8 g/m^2),4311/m^2 (4.5 g/m^2), and 8558/m^2 (16.0 g/m^2 ) respectively.A substantial portion of the benthic fauna was strandedand subsequently decreased rapidly in drying and frozensubstrates exposed to atmosphere. Total benthic numbersand biomass were greatest immediately below the drawdownlimit.Recolonization required three months {mid-March tomid-June, 1974) to attain pre-drawdown values for numbersand biomass, and subsequently both were greater afterreinundation than before the substrate was exposed.Recolonization of areas exposed to the atmosphere wasgreater in substrates containing large amounts of organicmatter than in sandy areas containing little organic matter.Sorting and transportation of sediments redistributed organic materials from the regulated zone to below the drawdownlimit, and macrophytes were eliminated from the regulatedzone. When compared to other reservoirs and lakes, thedensity of benthos in the Big Eau Pleine Reservoir canbe neither regarded as high nor low. However, whencompared with non-fluctuating reservoirs the number ofEphemeroptera, Plecoptera, Trichoptera, Amphipoda, andGastropoda was low.

[发布机构] University of Wisconsin-Stevens Point