Prolonged drought increases environmental heterogeneity and plankton dissimilarity between and within two semiarid shallow lakes over time

Abstract

Extreme weather events are likely to become more frequent in the future due to climate change, and how they will affect communities is a major challenge to ecologists. In this study, we assessed the effects of a prolonged drought on environmental heterogeneity (EH) components and phytoplankton and zooplankton α, β and γ diversities between and within two tropical semiarid shallow lakes. We hypothesize that prolonged droughts decrease phyto- and zooplankton α and γ diversities, increase between-lake and within-lake EH and accordingly increase plankton species replacement over time. To test this, we performed generalized least squares and general linear regressions to relate the effects of time and EH on the diversity components of phyto- and zooplankton assemblages and separately by their size groups (nano, micro- and mesoplankton). In agreement with our hypothesis, our results showed that between-lake $\overline{\alpha }$ and γ diversities from phytoplankton and zooplankton (and their respective size classes) were generally negatively related to EH, whereas the plankton β diversity showed an opposite pattern at both within-lake and between-lake scales. In a dry future, actions to improve water quality and water use will be needed to reduce the risk of biodiversity loss and water deterioration within and across lakes over time.