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

Abstract

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.