Characteristics of cladoceran and copepod communities in floodplain habitats of the Atchafalaya River Basin

In the summer of 1994, floodplain habitats of the Atchafalaya River Basin w ere surveyed for cladocera and copepoda. Collection sites were grouped into three distinct habitat types (black-water, brown-water and green-water) ba sed on a principal components analysis of five hydrographic variables (curr ent velocity, Secchi disk depth, surface percent saturation of dissolved ox ygen, dissolved oxygen differential and surface water temperature). An ANOV A of four community indices (total abundance, Shannon-Weiner diversity (H') , richness, and evenness) was performed on both cladoceran and copepod comm unities among the three floodplain habitats. Common species were compared a mong habitats (chi (2) goodness-of-fit) to determine where they were most a bundant. Green-water habitats had the greatest overall abundance of cladoce rans and copepods (dominated by Diaphanosoma birgei, Moina micrura and Meso cyclops edax), but ranked lower in diversity and evenness than black-water and brown-water habitats where Ilyocryptus spinifer, Simocephalus serrulatu s, Macrocyclops albidus (black-water) and Bosmina longirostris and Acanthoc yclops vernalis (brown-water) were most abundant, respectively. These resul ts indicate that the mosaic of floodplain habitats within large temperate r iver systems support unique zooplankton communities, and that these habitat s are largely a function of seasonal hydrographic features.