Phytoplankton Dynamics and Urbanization Gradients Reshape Dissolved Organic Matter and Microbial Networks across a Freshwater Estuary

Urbanization reshapes dissolved organic matter and microbial networks across a freshwater estuary, with sediment OM shifting from aromatic terrestrial signatures to N-rich protein and amino-sugar-like compounds.

• Why it matters: Watershed development degrades water quality and alters organic matter and community structure, but how land use gradients translate into estuarine ecosystem function remains unclear.
• What they did: Across six sites spanning an urbanization gradient, the study combined FTICRMS characterization of water and sediment OM with 16S and 18S rRNA gene amplicon sequencing plus nutrients, ions, turbidity, temperature, phytoplankton biovolume, and land use.
• The result: Sediment microbial dissimilarity was strongly associated with phytoplankton biovolume, linking benthic-pelagic coupling, while pelagic OM and microbes tracked seasonal gradients and transient phytoplankton dynamics modulated by urban inputs.