AQUATIC INVERTEBRATE ECOLOGY DURING A SIMULATED BOTULISM EPIZOOTIC INA SACRAMENTO VALLEY WETLAND

We investigated the effect of decomposing duck carcasses on aquatic in vertebrate numbers, biomass, and taxonomic composition in a seasonally flooded, impounded wetland in the Sacramento Valley, California durin g August-November 1988 and 1989. Major invertebrate taxa were copepods (Cyclopoida, occurred in 8.3% of samples), water fleas (Daphnidae, 8. 9%), water boatmen (Corisella, 10.4%), and midge larvae (Goeldichirono mus, 9.3%; Chironomus, 11.5%; Tanypus, 17.2%). We found no treatment ( carcass present or no carcass) by sampling day interaction for these t axa. We found a significant difference between sample plots with carca sses and those without carcasses only for Daphnidae counts and Corisel la wet weights. We found significant differences among sampling days f or these taxa that were probably statistical artifacts. We were unable to detect any effect of duck carcasses on aquatic invertebrate commun ity structure and the potential availability of invertebrates as water fowl food.