Ocean 'Dead Zones' Are Releasing One of The Worst Greenhouse Gases
ENVIRONMENT 05 July 2021
By BRETT JAMESON, THE CONVERSATION
In October 2019, I set sail with a team of scientists aboard the Canadian Coast Guard Vessel John P. Tully in the northeast Pacific Ocean, off the coast of Vancouver Island.
Battling rough seas and lack of sleep, we spent the better part of a week working shoulder-to-shoulder in a small stand-up refrigerator, analyzing seafloor sediments to learn more about the effects of low-oxygen conditions on deep-sea environments.
When organisms die, they sink through the water column, consuming oxygen in the sub-surface ocean as they decompose. This leads to bands of oxygen-depleted water called oxygen minimum zones, or "dead zones".
These harsh environments are uninhabitable for most organisms. Although they occur naturally in some areas, dead zones often appear after fertilizer and sewage wash downstream into coastal areas, sparking algal blooms, which then die off and decompose.
One of our studies from that expedition suggested that the sediments below oxygen-depleted waters are a significant source of nitrous oxide (N2O). This gas is released into the atmosphere when deep water rises to the surface in a process known as upwelling.
Nitrous oxide, more commonly known as "laughing gas", is a potent greenhouse gas, 300 times more powerful than carbon dioxide.
Global emissions of N2O are increasing as a result of human activities that stimulate its production.
