Lack of oxygen a key stressor on marine ecosystems
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An analysis by Professor Bob Diaz of the Virginia Institute of Marine Science (VIMS) and Swedish researcher Rutger Rosenberg shows that the number of “dead zones”—areas of seafloor with too little oxygen for most marine life—has increased by a third between 1995 and 2007. Dead zones are now a key stressor of marine ecosystems and rank with over-fishing, habitat loss, and harmful algal blooms as global environmental problems.
Diaz and Rosenberg record 405 dead zones in coastal waters worldwide, affecting an area of 95,000 square miles, about the size of New Zealand. The largest dead zone in the U.S., at the mouth of the Mississippi, covers more than 8,500 square miles, roughly the size of New Jersey. A dead zone also underlies much of the main-stem of Chesapeake Bay, each summer occupying about 40% of its area and up to 5% of its volume.
Dive deeper to find out
- How and where dead zones form
- How rapidly the number of dead zones has increased through time
- How dead zones affect marine organisms, communities, and ecosystems
- How climate change may affect dead zones, and
- How scientists, policymakers, and citizens are collaborating to reduce dead zones.
Ocean in Google Earth
Users can access Diaz's dead zone data within the newest version of Google Earth by opening the "Layers" pane and navigating to Ocean/State of the Ocean/Dead Zones. The program can be downloaded for free by browsing to http://earth.google.com/ocean. Each dead-zone location in Google Earth (marked by a skeletal fish icon) includes data on the nature of the dead zone (periodic, seasonal, or persistent), its size, the date it was first observed, its impact on fisheries, its impact on deep-water ecosystems, and a reference.
Diaz plans to continue to update his dead-zone database as new information becomes available.