Eutrophication decrease compositional dissimilarity in freshwater plankton communities.

Area of Science:

• Freshwater ecology
• Aquatic biodiversity
• Plankton community dynamics

Background:

• Human activities like land use change and eutrophication pose significant threats to freshwater biodiversity and ecosystem functioning.
• Plankton communities, comprising bacteria, algae, and zooplankton, are crucial components of aquatic ecosystems.

Purpose of the Study:

• To investigate the alpha- and beta-diversity of plankton communities in lakes of the Yangtze River Basin.
• To determine the influence of environmental variables, particularly trophic status and heterogeneity, on plankton community structure.
• To elucidate the relationships between plankton diversity, biomass ratios, and trophic interactions.

Main Methods:

• Utilized classical microscopy and high-throughput sequencing for plankton analysis.
• Analyzed 40 lakes in the Yangtze River Basin, assessing environmental variables.
• Employed non-metric multidimensional scaling, mantel tests, and structural equation modeling.

Main Results:

• Plankton community dissimilarities (bacteria, algae, zooplankton) decreased with increasing trophic status index (TSI).
• Environmental dissimilarity positively correlated with plankton compositional dissimilarities.
• Zooplankton richness and dissimilarity positively influenced the zooplankton/phytoplankton biomass ratio, with indirect effects mediated by algae.

Conclusions:

• Eutrophication, indicated by increased trophic status and reduced environmental heterogeneity, may weaken trophic cascades.
• Reduced top-down control by zooplankton on phytoplankton due to eutrophication impacts food web dynamics.
• Understanding these relationships is vital for freshwater ecosystem management and conservation.