Carbon flux and hypoxia in the Chesapeake Bay

The Chesapeake estuary is the largest in the United States, with more coastline than the entire West Coast. It is one of the most extensively studied aquatic environments in the world. Yet, the inorganic carbon chemistry of the main stem has not been studied, which seriously limits our ability to understand and predict acidification in this large and seasonally hypoxic/anoxic bay. This is an acute problem for resource managers trying to anticipate, monitor and react to ocean acidification. Although most of the estuary is shallow, in the main stem there is a persistent low pH and hypoxic/anoxic zone during the summer through which we can describe the interaction between hypoxia and acidification. A very low pH minimum (~7.2) was observed at the oxic and anoxic boundary layer, indicating a highly dynamic link of acid-base chemistry to redox reactions and physical mixing. We present several years of observations that begin to describe a baseline of spatial, temporal, and depth profiles of the carbon system in the Chesapeake Bay and possible changes in pH over time.