Biogeography and Edaphic Factors Structure Coastal Sediment Microbial Communities More than Vegetation Removal by Sudden Vegetation Dieback

Development of sudden vegetation dieback (SVD), a phenomenon that causes the rapid mortality of salt marsh plants, specifically Spartina alterniflora , has affected large-scale alterations in Atlantic coastal systems, through the often-complete removal of vegetation. In this study, two wetlands that differ in the time since development of SVD were compared in order to study biogeographic and temporal patterns that structure coastal wetland microbial communities and their response to disturbance. Biogeographic and edaphic factors that distinguished the two wetlands, such as differing salinity, water content, and soil carbon and nitrogen between the sites were more strongly associated with sediment microbial community structure than either sampling date or SVD development. In fact, no OTUs differed in abundance due to the season samples were collected, or vegetation loss due to SVD. This is not to say that SVD did not alter the composition of the microbial communities. The taxonomic composition of sediment communities in SVD-affected sediments was more heterogeneous between samples and a small number of OTUs were enriched in the vegetated sediments. Yet, these data suggest that coastal wetland sediment communities are predominantly shaped by environmental conditions and are generally resilient to temporal cycles or ecosystem disturbances. Importance One of the challenges of microbial ecology is predicting how microbial communities will respond to ecosystem change. Yet, few studies have addressed whether microbial responses to disturbance are consistent over space or time. In this study we employ SVD as a natural vegetation removal experiment and compare the sediment microbial communities between two geographically separated wetlands ( ca 125 km). In this manner, we uncover a hierarchical structuring of the microbial communities, being predominantly governed by biogeography, with lesser effects due to disturbance, or temporal dynamics.