Bacterial communities in the vegetated sediments by Suaeda japonica and unvegetated mud flat in Ganghwa intertidal wetland of the Han River estuary, Yellow Sea

Abstract

Bacterial community plays a key role in maintaining the ecological function of intertidal wetlands. In this study, bacterial communities, along with a variety of geochemical parameters, were characterized in the vegetated sediments by Suaeda japonica (SJ site) and unvegetated mud flat (UMF site) at Ganghwa intertidal wetland using Illumina next-generation sequencing. The geochemical parameters and bacterial communities showed evident differences not only between surface sediment layers of two sites, but also between surface and deep layers. The rates of organic carbon oxidation and iron-reduction were higher at the surface layer with S. japonica roots in SJ site than that of UMF site, and Desulfuromonadaceae including several iron-reducing bacteria were predominantly found in the surface layer of SJ site. Meanwhile, Psychromonadaceae and Flavobacteriaceae, macromolecule (e.g., chitin and cellulose) degraders, were the most dominant groups found in the surface layer at the UMF site. This is extrapolated because macrofauna that inhabit in Ganghwa intertidal wetland act as potential sources of organic substrates for microbes, or because their bioturbation affects the bacterial community structures. At deep sediment layers of both sites, the reduced compounds were accumulated and anaerobic/facultative anaerobic bacteria groups abundantly distributed. The associations of bacterial communities and geochemical parameters indicated that the dominant members of each site might be attributed to the difference of environmental conditions (i.e., vegetation and the availability of organic matter). However, to more precisely evaluate the values of Ganghwa intertidal wetland ecosystem, it is necessary to study the activity and function of microbes associated with biogeochemical processes in the future.