A new study suggests nearly all ocean dead zones will increase in size by the end of the century as a result of climate change.
Dead zones are regions where the water has an extremely low oxygen content, causing any sea creatures that wander into them to die, the Smithsonian reported. Dead zones do occasionally form naturally, but can also be triggered by runoff from farms and cities carrying nutrients such as nitrogen and phosphorous. These nutrients then feed large blooms of algae, which decompose and suck up all of the oxygen in the process.
These dead zones, or "hypoxic" areas, have doubled in size every decade since the 1960, mainly because of a steady increase in nutrient runoff. Researchers predicted that climate change will only exacerbate the growing problem. To make their findings the researchers looked at 400 dead zones across the globe; about 94 percent of these regions will experience a warming of about 3.6 degrees Fahrenheit by the end of the century.
"Temperature is perhaps the climate-related factor that most broadly affects dead zones," researchers Andrew Altieri of the Smithsonian Tropical Research Institute in Panama and Keryn Gedan of the University of Maryland, College Park, and the Smithsonian Environmental Research Center in Maryland wrote in the paper that appears today in the journal Global Change Biology.
Warmer surface waters are less likely to mix with the colder water below, making it more likely to run out of oxygen. As temperatures increase marine creatures such as fish and crabs also need more oxygen to survive.
"That could quickly cause stress and mortality and, at larger scales, drive an ecosystem to collapse," the researchers wrote.
Other aspects of climate change, such as an earlier arrival of the summer season, can also influence dead zones. Early-onset summers can cause hypoxia to start developing prematurely as well as expanding to cover larger regions.In the future, the expansion of dead zones can be reduced by cutting down on nutrient pollution.
"Climate change can have a variety of direct and indirect effects on ocean ecosystems, and the exacerbation of dead zones may be one of the most severe," the researchers wrote.
