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Presented at the NABS Annual meeting, Anchorage, Alaska, 2006
in Large River Ecology
Invertebrate macrobenthos in three large reservoirs of the upper Missouri River
J.V. Scharold, T.D. Corry, D.W. Bolgrien, and T.R. Angradi.US EPA Mid-continent Ecology Division, Duluth, MN 55804
Although benthic macroinvertebrates have been used as indicators of ecological condition for a variety of aquatic ecosystems, reservoirs on large rivers present unique problems for assessment design, because they combine the characteristics of lotic and lentic systems. The purpose of this study was to characterize benthic macroinvertebrate assemblages of three upper Missouri River reservoirs. A probability design was used to select sites from Lake Oahe, Lake Sakakawea, and Fort Peck Lake. Sites were chosen to represent the main stem of each reservoir, as well as small, medium, and large bays. Benthos was collected with a PONAR dredge. Mean (+SE) total abundance of benthic macroinvertebrates in the main stem of the reservoir was 1584 +628/m2 in Lake Oahe, 1979 +238/m2 in Lake Sakakawea, and 838 +249/m2 in Fort Peck Lake. The assemblage was dominated by oligochaetes (52-62% of total organisms) and chironomids (24-33%). Small and medium-sized bays generally had greater total abundances, particularly of chironomids and the burrowing mayfly Hexagenia. Composition and abundance of the benthos was strongly influenced by depth. Information on the abundance, distribution and variability of benthic macroinvertebrates will be used to further refine assessment strategies for large reservoirs. This abstract does not necessarily reflect USEPA policy.
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