Temporal changes in zooplankton species diversity in response to environmental changes in an alluvial valley

Monitoring the components of diversity may provide important information about diversity dynamics and processes that modify ecosystems. We investigated the temporal diversity of the zooplankton groups (testate amoebae, rotifers and microcrustaceans) over ten years (2000–2009) at local and regional scales in the alluvial valley of the Upper Paraná River in order to test: temporal changes in alpha, beta and gamma diversities of zooplankton groups, association of diversity dynamics with environmental factors, and synchronisation in temporal diversity between different subsystems. The gamma and alpha diversities of testate amoebae increased over time, while that of rotifers decreased. In contrast, microcrustacean diversity did not show a linear temporal trend. Beta diversity of microcrustaceans and rotifers increased over time. The models of temporal diversity variation explained between 10% and 46% of the total variability. Inorganic solids suspended and chlorophyll a were the environmental predictors selected in the models of best fit. Alpha diversity showed spatial synchronisation, suggesting that the regional dynamics contributed to the temporal variation of diversity. Zooplankton diversities followed a temporal dynamics in response to local and regional factors (water level, inorganic solids suspended and chlorophyll a), but the groups showed different responses. Thus, we corroborated the hypothesis of diversity synchrony of each zooplankton group between the sub-systems, but the responses to the environmental variations were found to be dependent on the group studied.