Chesapeake Biological Laboratory Assistant Professor Dr. Jeremy Testa has completed modeling work that shows how nutrient loading affects oxygen levels in the Chesapeake Bay.
Aquatic organisms need a certain amount of dissolved oxygen in the water to survive. A shortage of oxygen is a phenomenon known as hypoxia. Fish and crabs must leave their preferred habitats when the area becomes hypoxic; when they are unable to escape, many die in an event known as a fish kill.
Hypoxia has become an increasing threat to the water quality and food webs of the Bay over the last several decades. One of the leading causes is nutrient loading, the process of large amounts of nitrogen and phosphorus entering the water from the atmosphere and land. These nutrients often come from human activities, like fertilizing crops and lawns, sewage treatment effluents, or generating power, and encourage the growth of algae that ultimately use up the oxygen in the water.
Testa’s computer-based modeling system allows scientists to plug environmental data into a linked set of equations to simulate the effects of nutrient loading on the Bay. When Testa ran these simulations, the model showed that nitrogen causes more harm to the Bay than phosphorus, and that downstream areas are more sensitive to nitrogen loading.
The model helps scientists understand how environmental processes impact both long and short-term changes in dissolved oxygen and will guide management efforts to reduce hypoxia in the Chesapeake Bay. Testa’s work shows that by reducing the amount of nitrogen entering the water and targeting the areas where the most harm occurs, policymakers and the public can help the Bay breathe better.
