Coastal wetlands are among the most ecologically valuable and economically important ecosystems on Earth, but also especially vulnerable to human pressures and climate change. These rich in biodiversity and highly productive ecosystems are known "hot spots" of biogeochemical exchanges, large reservoirs of soil organic matter, and important sources of dissolved organic matter (DOM) to estuaries and coastal oceans. However, there is presently very little understood about the biotic and abiotic processes in these large carbon reservoirs (marsh soils) that regulate the quantity and quality of DOM exported to estuaries, and ultimately the processing of DOM in the estuarine water column. Research in our Lab integrates field measurements with advanced remote sensing observations and new mechanistic carbon cycling modeling to address key research hypotheses that are critical for understanding the role of marsh soils and tidal wetland-estuary margins as buffers, reactors, and transformers of dissolved organic carbon and nutrients. Results from these studies are used to improve coastal water quality assessment, guide sustainable management of these highly valuable natural resources, and predict potential responses of wetlands to future pressures.