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Updated: Sep 18, 2025

Chemotactic Response of Marine Micro-Organisms to Micro-Scale Nutrient Layers
Published on: May 28, 2007
Salinity regulates nutrient cycling via top-down and bottom-up forces in artificial cut-off tidal channels: Insights
1State Key Laboratory of Water Cycle and Water Security, College of Hydrology and Water Resources, Hohai University, Nanjing 210098, PR China.
Abstract:
Artificial cut-off of natural tidal meanders for flood control has substantially altered microbial communities and their role in nutrient cycling, yet the lack of comprehensive investigations into these specific anthropogenic impacts introduces greater uncertainty regarding the resultant water quality of nutrient-enriched estuaries. Here, we investigated how planktonic multitrophic microbiota and their mediated nutrient cycling respond to artificial meander cut-off using the environmental DNA (eDNA) approach. Results showed that despite the decline in α diversity of multitrophic microbiota, the nutrient cycling potential of the water column was enhanced 2.91-fold in the straight tidal channel. The artificial cut-off restructured the microbial food web, with trophic transfer efficiency from basal species to protozoa increasing. Salinity was identified to be the key environmental driver, mitigating the negative impact of decreased biodiversity on estuarine nutrient cycling potential by intensifying protozoan predation on heterotrophic bacteria (top-down forces). Additionally, salinity further enhanced environmental selection (bottom-up forces), reducing heterotrophic bacterial diversity while promoting the proliferation of functional microbial taxa, such as Comamonadaceae, Chitinophagaceae, and Rhodocyclaceae. This study offers novel insights into nutrient cycling in artificial straight tidal channels and provides critical foundations for optimizing restoration and management strategies in anthropogenically modified tidal river.
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