Most attention about oxygen-depleted water in the Chesapeake Bay is focused on the "dead zone" that forms in deep water each year. But most oxygen-related fish kills actually take place in shallow waters, where recent research has shown there are often rapid swings in oxygen levels from day to night.

The National Oceanic and Atmospheric Administration gave a team of researchers a five-year grant estimated at nearly $1.6 million to improve predictions of the impact of low-oxygen water on commercially and ecologically important species such as oysters, summer flounder, striped bass and white perch.

The research team, led by Denise Breitburg of Smithsonian Environmental Research Center in Edgewater, MD, also includes scientists from the University of Delaware and Louisiana State University.

Results of the study will help officials pinpoint key areas for habitat and fisheries restoration, and better protect shallow water habitat that serves as critical nursery areas. "Finding out when and where low oxygen 'swings' occur will help state and federal agencies make important management decisions related to the Bay's coastal and marine ecosystems," said Peyton Robertson, director of the NOAA Chesapeake Bay Office.

When the oxygen level is low, it can compromise the growth, reproduction and immune responses of fish and other species. Although low-oxygen conditions can occur naturally, they are often worsened by excess nutrients, which spur algae blooms. The algae draws oxygen from the water as they die and decompose.

The researchers also plan to study acidification of the Chesapeake Bay, which is also linked to low-oxygen conditions and may exacerbate the impact on fish and oysters.

"This research will enhance our efforts to accelerate the restoration of the Chesapeake Bay and contribute to the re-establishment of fisheries that have suffered steep declines during the past decades," said Sen. Benjamin Cardin, D-MD. "The Bay provides thousands of jobs to the region, and we have a responsibility to improve the health of this treasured resource for generations to come."