We are investigating the impacts of extreme daily fluctuations in oxygen and pH on fish and invertebrates in the Chesapeake Bay. The modeling tools we produce will improve the ability to predict effects of nutrient enrichment and management actions on living marine resources at local and regional scales. In addition, the models will improve ecological and fisheries restoration and water quality monitoring activities.

Why We Care
Low dissolved oxygen is increasingly prevalent and severe, negatively affecting animal growth, reproduction, and survival. Waters are hypoxic when oxygen concentrations are low enough to negatively affect growth, reproduction, or survival of exposed animals. It is caused or worsened by a combination of the geology of an ecosystem, nutrient enrichment, and warming sea temperatures.

Hypoxia conditions are commonly studied on large geographic scales (e.g., the Gulf of Mexico “dead zone” or Chesapeake Bay), thus there is a need for studies that will improve our understanding of hypoxia impacts on smaller scales such as predicting effects on upper trophic level species (e.g., fish, mollusks and crustaceans) across a variety of space and time scales. This is especially true for productive shallow water systems that may negatively affect fish and shellfish within the shallow habitats and the productive areas where deep and shallow water habitats converge. Accompanying day-night swings in pH (a scale used to measure acidity) may increase the impacts of hypoxia, and the combination of these factors may lead to more severe effects than predicted by lab experiments that examine effects of low oxygen in isolation.

What We Are Doing
We will determine the relationship between diel-cycling pH and hypoxia in shallow water habitats within the Chesapeake Bay system and characterize how often economically and ecologically important fish and shellfish species experience these conditions in the field. We will also test the individual and interactive effects of these stressors on juvenile growth, mortality and reproduction of finfish and oysters. Another response we will look for is whether pH and hypoxia fluctuations affect the occurrence of protozoan parasite Perkinsus matinus infections (“Dermo”) in oysters.

We will use the data we collect to refine models that predict effects of diel-cycling hypoxia and pH fluctuations on fish and oysters under conditions experienced in Chesapeake Bay. Spatially (location) oriented food web models will be used to predict, under a range of management scenarios, how shallow water diel-cycling oxygen and pH–affected systems might recover from lost production resulting from seasonal bottom-water hypoxia and estimate the sustainable fishing yields of affected commercial fisheries species living in Chesapeake Bay.

This work is part of the Coastal Hypoxia Research Program (CHRP). The project team is led by Dr. Denise Breitburg of the Smithsonian Institution’s Environmental Research Center with co-investigators from the University of Delaware, Louisiana State University, Maryland Department of Natural Resources, NOAA Fisheries, and U.S. EPA.

What We Are Finding
The project is producing a group of management-relevant data and predictive modeling tools that will improve the ability to predict effects of nutrient enrichment and management actions on living marine resources at local and regional scales. In addition, the models will improve ecological and fisheries restoration and water-quality monitoring activities, especially as appropriate for shallow water habitats that serve as critical nursery areas. Close collaboration among the investigators, the project’s special management partnership team, and other regional managers will help ensure the usefulness of the research and transfer of the research results into ecosystem and living resource management and restoration plans.