AI Insight
This study examined how urban development affects freshwater estuaries by analyzing water chemistry, organic matter composition, and microbial communities across six sites with varying urbanization levels. Researchers found that urban pollution impacts water and sediment differently: water column communities responded to seasonal changes and temporary phytoplankton blooms driven by urban nutrients, while sediment communities showed direct, long-term responses to urbanization with increased nitrogen-rich organic matter in urban areas compared to plant-based matter in rural sediments. Both water and sediment ecosystems showed abrupt shifts in microbial and algal communities at specific urbanization thresholds, with strong coupling between bottom-dwelling microbes and floating phytoplankton populations.
Why it matters
These findings suggest that monitoring both water and sediment is essential for assessing urban impacts on estuaries, as each compartment captures different temporal scales of ecosystem change. Understanding these non-linear thresholds could help city planners identify critical development limits to protect estuary function in nutrient cycling, contaminant processing, and biodiversity support.
Understand the Science
⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Freshwater estuaries process contaminants, cycle nutrients, and support biodiversity. However, watershed development degrades water quality, alters organic matter (OM) composition, and reshapes microbial and phytoplankton communities. Understanding how anthropogenic land use shapes estuarine ecosystem function remains a key challenge. We evaluated relationships among benthic and pelagic biogeochemistry, algal, and microbial communities across six sites along an urbanization gradient, combining FTICRMS characterization of water and sediment OM, with 16S and 18S rRNA gene amplicon sequencing of bacterial/archaeal and algal assemblages, alongside measurements of nutrients, ions, turbidity, temperature, phytoplankton biovolume, and land use. Pelagic OM and microbial variation tracked seasonal gradients and transient phytoplankton dynamics modulated by urban inputs, whereas sediments responded directly to urbanization: urban sediments were N-rich with protein, and amino-sugar-like OM, while rural sediments carried aromatic, terrestrial, plant-derived signatures. Both compartments showed non-linear responses, with microbial, algal, and OM abundances shifting abruptly across urbanization thresholds. Strong associations between sediment microbial dissimilarity and phytoplankton biovolume indicate benthic-pelagic coupling, whereby urban nutrients putatively stimulate phytoplankton growth and subsequent OM deposition restructures benthic assemblages. Thus, pelagic communities capture transient urban effects mediated by phytoplankton, whereas benthic communities integrate chronic impacts, highlighting the value of compartment-specific monitoring in estuarine ecosystems.