Benthic Macroinvertebrates in the Big Eau Pleine, a Fluctuating, Central Wisconsin Reservoir
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Date
1976-08Author
Kaster, J. L.
Publisher
University of Wisconsin-Stevens Point
Metadata
Show full item recordAbstract
Benthic macroinvertebrate distribution, abundance,
and composition were observed in a fluctuating {7.7 m)
central Wisconsin reservoir during 1973-1974. Chironomidae
and Oligochaeta represented 98 percent of the total
fauna by number. The chironomid, Chironomus plumosus,
and oligochaete, Limnodrilus sp., each averaged 36 percent
of the total benthic biomass. Annual mean numbers and
biomass in areas exposed to atmosphere, exposed to ice
cover, 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 stranded
and subsequently decreased rapidly in drying and frozen
substrates exposed to atmosphere. Total benthic numbers
and biomass were greatest immediately below the drawdown
limit.
Recolonization required three months {mid-March to
mid-June, 1974) to attain pre-drawdown values for numbers
and biomass, and subsequently both were greater after
reinundation than before the substrate was exposed.
Recolonization of areas exposed to the atmosphere was
greater in substrates containing large amounts of organic
matter than in sandy areas containing little organic matter.
Sorting and transportation of sediments redistributed organic materials from the regulated zone to below the drawdown
limit, and macrophytes were eliminated from the regulated
zone. When compared to other reservoirs and lakes, the
density of benthos in the Big Eau Pleine Reservoir can
be neither regarded as high nor low. However, when
compared with non-fluctuating reservoirs the number of
Ephemeroptera, Plecoptera, Trichoptera, Amphipoda, and
Gastropoda was low.