Featured Image Credit: Peter Bondo Christensen
By Sarah Sharkey
“Dead zones” are patches of low-oxygen waters that are threatening marine ecosystems around the world. Basically, without a higher oxygen concentration more fish die.
According to the U.S. National Oceanic and Atmospheric Administration (NOAA), the dead zone in the Gulf of Mexico this year is the third largest recorded since 1985. The dead zone is the result of a combination of runoff from municipal wastewater and agricultural fertilizers.
Extra nutrients sounds like a good thing at first right? Well, all of these extra nutrients stimulate algae blooms which eventually die off. As they decompose and sink to the bottom of the ocean they absorb most of the oxygen in the water around them, which creating a dead zone.
With the higher stream levels of this past year, more nutrients will be making it to the ocean. This input of too many nutrients have experts predicting that the dead zone will grow to the size of New Jersey this year.
There is another type of oxygen low ocean area, one that persist year round. Oxygen-deficient zones occur naturally in equatorial waters of the eastern ocean basins. These zones are natural and weren’t really considered a real problem until recently.
With the increase of carbon dioxide in the air due to anthropogenic activities, oxygen-deficient zones are expected to expand. These expansions presumably will have negative effect on marine life.
We haven’t really heard a lot about deoxygenation. Woods Hole Oceanographic Institution scientist, Mak Saito, said, “We’ve heard about the warming effects for a long time. And we’ve heard about the acidification effects for about a decade or so now. But deoxygenation is one of the newer problems we’re realizing is out there.”
Less oxygen means less fish. This means less food and lost livelihoods.
Scientists are currently trying to figure out exactly how deoxygenation will play out in our oceans. The more they can learn, the better prepared we will be in the future.