Approximately 50% of the population lives on coastal areas, which are increasingly at risk of saltwater inundation due to sea level rise (SLR). As a result of SLR, lower crop yields are produced by farmland, and “ghost forests” take the place of healthy forested land. The processing of organic matter changes as the landscape is altered. Climate change is also inducing changes to coastal hydrology through fast (e.g. intense storms) and slow (e.g. SLR) processes. Consequentially, aquatic dissolved organic matter (DOM) composition and structure may be altered with implications to other important biogeochemical processes (e.g. nutrient cycles, redox speciation). The carbon source for heterotrophic bacteria is influenced by DOM composition, which may in turn affect the coastal microbiome. For this study, bulk and molecular level DOM characteristics were analyzed from paired agricultural and forested sites on the Chesapeake Bay, Delaware Bay, and Atlantic Ocean. Preliminary data shows that there are higher concentrations of carbon and chromophores in forested sites than agricultural sites, as quantified by higher specific UV absorbance at 254 nm (SUVA<sub>254</sub>). Further, we observed different responses to DOM concentrations released from storms between forested and agricultural sites. In future work, we will continue to analyze detailed bulk and molecular DOM characteristics to determine how changes in landscape use coupled to climate change influences its composition and structure.

Compositional changes of dissolved organic matter due to sea level rise in the coastal critical zone

ACS Spring 2022

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