SREL Reprint #1974





Effects of Abiotic Factors on Macroinvertebrate Drift in the Lower Mississippi River, Louisiana


Savannah River Ecology Laboratory, Division of Wetland Ecology, Drawer E, Aiken, South Carolina 29802


Louisiana Cooperative Fisheries and Wildlife Research Unit, U.S. National Biological Service, 124 Forestry Bldg., Louisiana State University, Baton Rouge 70803

ABSTRACT.-We assessed the effects of abiotic factors on invertebrate drift composition in the lower Mississippi River from November 1984 to June 1985. We sampled drift, measured in situ water quality variables and recorded river stage and discharge 1 night each month. Principal component analysis (PCA) and standard multiple regression were used to investigate temporal relationships between drift and abiotic factors in a large river system. Several drifting taxa (Ephemeroptera, Trichoptera) were significantly, negatively related to discharge and positively related to temperature, current and conductivity. In separate analyses, collector, engulfing predator and detritivore feeding groups were significantly, positively related to stage/discharge and negatively related to current velocity. In addition, each trophic component had several prey and one predator highly correlated with it. Seasonal variability in drift was a response to both invertebrate predation and fluctuations in the hydrologic cycle. Our study could not distinguish between two main effects of river discharge on drift: dilution and habitat availability. The possibility that drift may be a separate community apart from the benthos, and thereby affected strongly by seasonal abiotic factors, is discussed.

SREL Reprint #1974

Koetsier, P. and C.F. Bryan. 1995. Effects of abiotic factors on macroinvertebrate drift in the lower Mississippi River. The American Midland Naturalist 134:63-74.

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