Image courtesy of Elizabeth Gates for LAT
To marine biologists, dead zones - low-oxygen areas that are unable to support most forms of life - represent one of the gravest manifestations of an ecosystem gone awry. Reported sightings of dead zones have surged over the last few decades as eutrophication incidents have become more common in coastal areas; some of the largest and recurring dead zones have been found along the coast of Oregon and Washington.
A team of marine ecologists at Oregon State University has determined that the increased occurrence of dead zones may be directly tied to global warming. As Kenneth Weiss reports in the Los Angeles Times, the researchers believe that stronger winds, brought about by higher land heat, are prolonging the natural process of upwelling, which brings deep nutrient-rich waters to the surface. Upwelling is a crucial process because it provides the raw nutrients for phytoplankton to grow, creating a rich source of food for filter feeders and small fish and, in turn, larger fish and other organisms higher up the food chain. Off the coast of Oregon, however, it becomes a case of too much of a good thing: Stronger and more persistent winds prolong the process, resulting in a surplus of nutrients and phytoplankton that isn't consumed - as a result, this large amount of food eventually sinks to the seafloor and rots, leading to the formation of low-oxygen, or anoxic, regions.
Worse yet, these dead zones have now spread to the region's prime fishing waters, threatening to extinguish an important sector of Oregon's economy. Jane Lubchenco, one of the lead scientists on the study, predicts that these incidents are only likely to become more frequent as greenhouse gas levels continue to rise, acidifying the oceans and heating up the land.