Relationships between environmental variables and the abundance of cladocerans and copepods in the Atchafalaya River Basin

Document Type

Article

Publication Date

12-1-1998

Abstract

The relationship of species abundance to eight environmental variables was tested for 24 common species of crustacean zooplankton collected in the Atchafalaya River Basin during the summer of 1994. Stepwise regressions (α = 0.05) revealed significant relationships between zooplankton abundance and at least one environmental variable for 18 species (R2 = 0.14 - 0.61, p < 0.0435 - 0.0001). The majority of these species' peak abundances were correlated with variables indicative of seasonal changes in floodplain habitat, as the Atchafalaya river receded, water temperature increased, and/or phytoplanktonic photosynthesis increased. Surface water temperature and the percent saturation of dissolved oxygen showed the most significant relationships, but specific conductance, current velocity, and Secchi disk depths were also related to abundance patterns of certain taxa. A principal components analysis of species abundances provided further insight into the partitioning of temporally-distinct zooplanton assemblages, showing that several species (Bosmina longirostris, Daphnia parvula, Eurytemora affinis, and Ceriodaphnia quadrangula) predominated during early summer, and were supplanted by a distinct late-summer assemblage (Diaphanosoma birgei, Moina micrura, Mesocyclops edax, and Daphnia lumholtzi) as time progressed. The transitional assemblage was dominated by Simocephalus serrulatus, Macrocyclops albidus, Microcydops rubellus, and Thermocydops inversus, all of which were most abundant in the hypoxic conditions characteristic of the latter stages of the Atchafalaya River flood-pulse. © 1998 Kluwer Academic Publishers.

Publication Source (Journal or Book title)

Hydrobiologia

First Page

175

Last Page

181

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