Dissolved organic matter, DOM, is a major reservoir of organic carbon in estuaries and the ocean. It plays a key role in coastal ecosystem ecology as a food source for microbes and a chemical reactant affecting water quality, carbon dynamics, production of greenhouse gases, nutrient availability, and phytoplankton activity. The absorption of ultraviolet (UV) and visible radiation by the colored component of the DOM pool, CDOM, drives much of marine photochemistry in open oceans and coastal waters. This project seeks to understand the role of tidal marshes as sources of DOM in the Chesapeake Bay, characterize landscape-scale variation in the quantity and quality of marsh-exported DOM, and understand the implications of such variation in the quantity and quality of marsh-exported DOM, and understand the implications of such variation for water optics and biogeochemistry in coastal margin ecosystems.
The abundance of marshes in the Chesapeake Bay (70,000 ha) make this an ideal place for addressing several key questions. Do the properties of marsh-exported DOM differ between freshwater and brackish systems? Are differences due to the types of plants the adjacent marshes support or due to variability in water chemical matrix? Do microbes grow differently on DOM from certain marsh types? And how do variability in plant community composition and environmental variables, such as salinity and pH, affect between-marsh variability in DOM optical quality, photo-reactivity and bioavailability? A comprehensive array of methods is used to answer these questions including field studies, optical properties, chemical analyses and novel laboratory studies. The ultimate goal is to better understand what regulates source and sink processes as DOM is transported from wetlands and tidal marshes to the coastal ocean. The research aims to improve our ability to use ocean color remote sensing to understand the Chesapeake Bay and other coastal zones, and increase our understanding of a key feature of the global carbon cycle.