What controls DOM composition variability in marsh-dominated estuaries?

Estuaries are complex environments with many variables affecting dissolved organic matter (DOM) composition. Uncovering which biogeochemical processes are the strongest factors in a given environment remains a challenge. In this context, the aim of this study is to characterize the dominant patterns of variability modifying the DOM composition in a typical estuary in the Southeastern US. We collected water samples during three seasons (July and October 2014 and April 2015) at both high and low tides, and conducted short (24 hours) and long-term (60 days) dark incubations. Samples were analyzed for bulk DOC, optical (CDOM), and molecular (FT-ICR MS) composition as well as for metatranscriptomics. Our first results showed that the dominant pattern modifying DOM composition in the region is seasonal, followed by tidal influence, and thirdly by bacterial degradation on short time scales. Results from the long-term incubations and from metatranscriptomics are currently being analyzed, and will be used for better assessing the dominant patterns of variability of DOM composition in the study area.