Seasonality and community structure of the backswamp invertebrates in a Louisiana cypress-tupelo wetland

Abstract

Core and floating “scoop” samples were taken monthly for two years in a Louisiana hardwood swamp for the characterization and identification of the benthic habitats far removed from waterways and bayous. Most backswamp macroinvertebrates have physiological and behavorial adaptations to withstand both desiccation and anoxia. The most ubiquitous taxa included amphipods, oligochaetes, diptera larvae, isopods, and fingernail clams. The biomass and density of backswamp benthic communities were some of the highest recorded for any “unpolluted” freshwater or estuarine soft-bottom habitat. The average number of invertebrates living in the sediments (5,690/m2) was significantly less than the numbers living in the floating mats ofLemna spp. (10,508/m2). The biomass distribution was just the opposite. There was a significantly greater invertebrate biomass in the sediments (8.4 g AFDW/m2) than in the floating vegetation (4.2 g AFDW/m2). Diversity (H) was relatively low, averaging only 1.8 in the floating vegetation and 1.4 in the sediments. Seasonal changes in density, biomass, and diversity were bimodal with peaks occuring during spring and fall, and were a function of the seasonality of wetland flooding and temperature.