Both fungi and prokaryotes are key drivers of biogeochemical processes in brackish and salt marshes. However, only a few studies have examined fungi and prokaryotes together and their potential interactions in marsh ecosystems. We performed a metabarcoding survey of prokaryotes and microbial eukaryotes in the sediment and overlying water column of the North Inlet salt marsh and the Winyah Bay brackish marsh in South Carolina, USA. We targeted the small and large rRNA genes (16S, 18S, 28S) and the internal transcribed spacer region (ITS2) during four seasons from 2020 to 2021. Early diverging fungi, primarily Zygomycota and Chytridiomycota, dominated brackish marsh communities. In contrast, salt marsh communities were dominated by Dikarya fungi, primarily Dothideomycetes in the water column and Sordariomycetes in sediments in the summer. In the autumn and winter, the dominant taxa in sediments shifted to Dothideomycetes. Network analyses revealed nearly exclusively negative interactions between fungi and prokaryotes in the sediment, suggesting competition. Zygomycota, Sordariomycetes, and Dothideomycetes were identified as potential keystone species in sediments. Interactions among early diverging fungi were primarily positive, suggesting a shared niche. Our work reveals novel fungal diversity in estuarine sediments and water column.  The identification of potential keystone species and their interactions with other microbial community members enables the design of targeted experiments to elucidate the mechanism of such interactions and their impact on biogeochemical cycles.

Primary Presenter: Madeleine Thompson, School of the Earth, Ocean, and Environment (mthompson@seoe.sc.edu)

Authors:

Madeleine Thompson, University of South Carolina  (mthompson@seoe.sc.edu)

Xuefeng Peng, University of South Carolina  (xpeng@seoe.sc.edu)