Co-occurrence of Bacillariophyceae-based- and Cryptophyceae-based planktonic food webs in a temperate estuarine ecosystem revealed via eDNA

We examined microbial food webs in Seomjin River and Gwangyang Bay in South Korea, using 18S rRNA amplicon sequencing of environmental DNA (eDNA) with a weighted gene correlation network analysis (WGCNA) – Cytoscape analysis, considering various environmental variables. WGCNA with weight >0.5 revealed two taxon-specific trophic interactions. One was composed of Chlorophyceae and Cryptophyceae-based primary producers and ciliates-based primary consumers. In another one, Bacillariophyceae was a main primary producer while rotifer and ciliates were primary consumers. The Bray-Curtis dissimilarity and correlation matrix of gene abundance with gene significance related to environmental variables showed that the Chlorophyceae and Cryptophyceae-based microbial food web was a function of dissolved inorganic nitrogen in the Seomjin River, whereas the Bacillariophyceae-based microbial food web was a function of dissolved inorganic phosphate in the Gwangyang Bay. Our study provides new insight into microbial food webs while considering the nutrient status of estuarine ecosystems.