摘要：We used bal and nocturnal zooplankton collections at 30 sites in the Atchafalaya River Basin (ARB) floodplain (Louisiana) to assess inter-habitat differences in diel vertical movements of numerically abundant cladocerans and copepods during the flood pulse. The magnitude of diel movement at each site was quantified with an index of vertical migration (VM)=log (nocturnal abundance 1)—log (diurnal abundance 1), and sites were grouped into lake (n=12), channel (n=9), and swamp (n=9) habitats based on principal components analysis of physicochemical characteristics. The cladocerans Diaphanosoma birgei and Moina micrura and the copepods Mesocyclops edax, Eurytemora affinis, and Acanthocyclops vernalis all exhibited siecantly greater VM values in lake habitats compared to swamp and channel habitats, and regression analyses indicated that the magnitude of nocturnal movements into the upper water column was related to the density of planktivorous fishes found at each site. Bosmina longirostris and Daphnia lumholtzi showed similar trends in VM among habitats, although data were highly variable, whereas Ilyocryprus spinifer exhibited no differences in diurnal and nocturnal densities in any habitat.
