The Influence of Habitat Availability, Connectivity and Limnological Conditions on Plankton and Macrophyte Biodiversity in Floodplain Lakes

Abstract

Under the current global disruption of natural hydrological dynamics of large rivers due to human activities, there is an urgent need to understand how hydrology influences freshwater biodiversity in riverine floodplains. The aim of our study was to disentangle the influence of aquatic habitat availability, aquatic habitat connectivity, and environmental conditions on the α-, β- and γ-diversity of phytoplankton, rotifers, microcrustaceans and macrophytes in shallow lakes from the Lower Paraná River floodplain. We conducted sampling campaigns during four hydrological conditions, including wet and extremely dry periods. We estimated the biodiversity of each biological group, assessed limnological conditions and calculated the availability and connectivity of aquatic habitats at both local (shallow lake) and landscape (floodplain) scales with active microwave Sentinel-1 and optical multispectral Sentinel-2 satellite data, combined with a geographic information system approach. To evaluate the influence of the studied variables on biodiversity, we applied generalised linear mixed models for α-diversity and a Mantel test for β-diversity. At the local scale, habitat availability and connectivity positively influenced overall α-diversity, while turbid and nutrient-rich conditions favoured phytoplankton but hindered microcrustacean α-diversity. At the landscape scale, β-diversity was more strongly associated with the heterogeneity of limnological conditions than with habitat connectivity, except for microcrustaceans, which were equally associated with both variables. Our study deepens the understanding of the main mechanisms of hydrology on the biodiversity of different biological groups and across spatial scales in the Lower Paraná River floodplain. Our findings underscore the critical importance of maintaining a dynamic hydrological regime to sustain essential floodplain processes that support aquatic habitats and promote biodiversity.