Taxon-specific effects of seasonal variation and water connectivity on the diversity of phytoplankton, zooplankton and benthic organisms in urban wetland

Climate change and human activities have altered the water environment and affected the community structure of aquatic organisms. Few studies have focused on the specific responses of multiple aquatic organisms, and their interactions, to environmental factors, particularly in urban wetland ecosystems. To address this gap, this study aimed to investigate the effects of seasonal variation and water connectivity on water properties and aquatic organisms in the Xixi wetland in Zhejiang Province, China. The results demonstrated that water properties showed significant differences with changes in the season and water connectivity, and the species richness, Shannon-Wiener index, Simpson diversity and Pielou evenness of aquatic organisms varied seasonally in riverways and ponds. Meanwhile, the response of various organisms to environmental factors was inconsistent. Dissolved oxygen and suspended solids greatly influenced phytoplankton, while water temperature was the principal factor affecting the diversity of zooplankton and benthic organisms. The partial least squares path model revealed that water properties had a significant direct positive effect on the diversity of the phytoplankton community, while it had a distinct direct negative effect on zooplankton community. Environmental factors influenced the diversity of benthic organisms through a trade-off way: directly through a significant negative effect on the benthic organisms, and through a significant positive effect on the phytoplankton, further influencing the benthic community in a significantly positive way. This study highlights the understanding of the patterns and underlying mechanisms of freshwater aquatic biodiversity, and the interaction of phytoplankton, zooplankton and benthic organisms to water environmental factors in freshwater ecosystems.