EFFECTS OF HYDROPERIOD AND PREDATION ON A MISSISSIPPI RIVER FLOODPLAIN INVERTEBRATE COMMUNITY

The objective of this study was to determine if pond permanence and ve rtebrate predation (by fish and waterfowl) affect invertebrate communi ty structure in the mudflat habitat of floodplain ponds. Invertebrate communities were studied for 1 year in four Mississippi River floodpla in ponds with different hydroperiods. Pond 1 experienced five dry peri ods, pond 2 experienced four, pond 3 dried once, and standing water re mained in pond 4 for the entire year. Vertebrate predator exclusion tr eatments (all access, no access, small-fish access and cage controls) were placed in all ponds. As pond duration increased, predatory invert ebrate richness and abundance increased while overall invertebrate ric hness and abundance decreased. With the exception of the cladoceran Di aphanosoma, all commonly encountered taxa were strongly affected by po nd permanence in terms of abundance, biomass and, generally, individua l biomass. Taxa were nearly early divided between those that were more abundant in less permanent ponds and those that were more abundant in longer-duration ponds. Invertebrate taxa richness, abundance, and tot al biomass were lower in the ah-access treatment than in the treatment s that restricted predator access, and these effects were stronger in the more permanent ponds. In general, there were no significant differ ences in responses to the treatments with small-fish access and no acc ess. These results support models that predict relatively weak effects of predation in frequently disturbed habitats.