Donald Scavia received funding from the National Science Foundation, the National Oceanic and Atmospheric Administration, the Environmental Protection Agency, the Erb Family Foundation, the Joyce Foundation, and the University of Michigan's Graham Sustainability Institute.
Scientists have identified a dead zone as large as Florida in the Gulf of Oman, which connects the Arabian Sea to the Persian Gulf. Around the world there are more than 400 current dead zones in oceans and lakes, where water contains so little oxygen that aquatic life can’t survive.
Dead zones form when aquatic organisms consume dissolved oxygen faster than it can be supplied. This typically happens when warmer water sits on top of colder water, or freshwater sits on top of saltier water - for example, where a river meets the sea. In either case the water on top is less dense and floats. The layers don’t mix much, so very little oxygen from the atmosphere reaches the lower layers.
But the biggest driver is nutrient pollution – excess inputs of nitrogen and phosphorus. These nutrients stimulate algae growth. They come from municipal and industrial wastewater treatment plants, and increasingly from fertilizer runoff from industrial-scale agriculture.
As my research has shown, large-scale dead zones are resistant to change. But nutrient reductions in the Chesapeake Bay are starting to improve conditions there. Communities around Lake Erie dramatically reduced its dead zone and toxic algae blooms in the 1970s by reducing phosphorus inputs. Now, however, these issues are resurfacing there – evidence that this problem is an ongoing challenge.