We are investigating how rising atmospheric temperature and changing precipitation patterns will affect coastal hypoxia (low dissolved oxygen) in Chesapeake Bay. Hypoxia in the bay, caused by an excessive influx of nutrients, is a key stressor for living marine and estuarine resources. We will help develop sustainable management actions to reduce nutrients in Chesapeake Bay in a changing climate.

Why We Care
Anthropogenic impacts, primarily in the form of excess nutrients derived from agriculture, sewage, and storm water runoff, have resulted in the degradation of coastal water quality and an increasing number of hypoxic events throughout the world. The Chesapeake Bay is the largest, most productive estuary in North America, providing crucial habitat for several native and migratory species. Benefits derived from the Bay are estimated to be more than $100 billion annually, while the watershed serves as home to more than 17 million people. Over the past century, rising population, urbanization, and fertilizer usage have led to increased nutrient inputs, productivity, and decaying organic matter, resulting in decreases in dissolved oxygen concentrations. The resulting increase in extent of hypoxia in the bay continues to threaten economic and ecosystem services provided by this natural resource. Potentially exacerbating hypoxia and the decline in water quality are the anticipated effects of climate change, such as increased temperatures, changes in precipitation patterns, and rising sea levels.
What We Are Doing
In 2010, total maximum daily load (TMDL) targets were set for Chesapeake Bay in response to Section 303(d) requirements of the Clean Water Act and President Obama’s 2009 Executive Order 13508 instructing federal partners to cooperate in the protection and restoration of Chesapeake Bay. The TMDLs were set based on two regulatory models for the watershed and estuarine water quality under current climate conditions. While this is a major step forward in the protection and restoration of the bay, it does not fully address how a changing climate will affect coastal hypoxia, specifically, increases in atmospheric temperature and changes in precipitation patterns.

To address this gap in information, we will quantitatively predict: (1) the impacts of future changes in climate and anthropogenic nutrient inputs on the extent of hypoxia in Chesapeake Bay; and (2) the impacts of climate change on the effectiveness of various alternative management actions designed to reduce hypoxia and improve water quality. We will use multiple existing models to develop scenarios: two mechanistic land ecosystem/watershed models (one academic and one regulatory) and two coupled estuarine water quality models (one academic and one regulatory). This will be the first time that alternative models will be compared against regulatory models. The use of models independent from the regulatory models will allow for evaluation of the robustness of the regulatory model predictions for nutrient loading and hypoxia.

This project is part of the Coastal Hypoxia Research Program, and is led by Marjorie Friedrichs (Virginia Institute of Marine Science, College of William & Mary). Project partners include Lewis Linker (Chesapeake Bay Program Office, Environmental Protection Agency); Gary Shenk (Chesapeake Bay Program Office, U.S. Geological Survey); Raymond Najjar (Pennsylvania State University); Hanqin Tian (Auburn University); and Eileen Hofmann (Old Dominion University).