Aquatic dead zones contributing to climate change

University of Maryland Center for Environmental Science: The increased frequency and intensity of oxygen-deprived “dead zones” along the world’s coasts can negatively impact environmental conditions in far more than just local waters. In the March 12 edition of the journal Science, University of Maryland Center for Environmental Science oceanographer Dr. Lou Codispoti explains that the increased amounts of nitrous oxide (N2O) produced in low-oxygen (hypoxic) waters can elevate concentrations in the atmosphere, further exacerbating the impacts of global warming, and contributing to ozone “holes” that cause an increase in our exposure to harmful UV radiation.

“As the volume of hypoxic waters move towards the sea surface and expand along our coasts, their ability to produce the greenhouse gas nitrous oxide increases,” explains Dr. Codispoti of the UMCES Horn Point Laboratory. “With low-oxygen waters currently producing about half of the ocean’s net nitrous oxide, we could see an additional significant atmospheric increase if these ‘dead zones’ continue to expand.”

Although present in minute concentrations in Earth’s atmosphere, nitrous oxide is a highly potent greenhouse gas and is becoming a key factor in stratospheric ozone destruction. For the past 400,000 years, changes in atmospheric N2O appear to have roughly paralleled changes in carbon dioxide CO2 and have had modest impacts on climate, but this may change. Just as human activities may be causing an unprecedented rise in the terrestrial N2O sources, marine N2O production may also rise substantially as a result of nutrient pollution, warming waters and ocean acidification. Because the marine environment is a net producer of N2O, much of this production will be lost to the atmosphere, thus further intensifying its climatic impact….

The Atchafalaya River Delta at the Gulf of Mexico, shot by the US Army Corps of Engineers