![Ocean dead zone in Gulf of Mexico [Image credit: Gabriella Ibarra via Flickr]](https://staticr1.blastingcdn.com/media/photogallery/2018/1/5/660x290/b_502x220x82/ocean-dead-zone-in-gulf-of-mexico-image-credit-gabriella-ibarra-via-flickr_1763099.jpg "Ocean dead zone in Gulf of Mexico [Image credit: Gabriella Ibarra via Flickr]")
ocean Dead Zones are growing larger. A recent study published in the journal Science states that the amount of ocean dead zones has quadrupled over the past fifty years. The main reasons cited involve changing concentration of nutrients and rising ocean temperatures. Rising heat content of Earth’s oceans can clearly be seen in publicly available data. Dead zones will have economic and societal consequences. Some solutions have been proposed.
Rising ocean temperatures, a major factor in dead zones
Since at least 1950, oxygen concentrations have been decreasing in both open ocean and coastal waters.
This loss of oxygen is referred to as deoxygenation.
By analyzing measurements of ocean oxygen levels at various sites around the globe, scientists have determined that oxygen-minimum zones (dead-zones) have expanded by several million square kilometers over the past fifty years. Furthermore, coastal areas now have oxygen concentrations that have fallen far enough to alter the chemistry of ocean water and limit the potential of aquatic life to survive there. Could this be a factor in the mass die-offs of marine life we have witnessed washing ashore in recent years?
As the paper published on Sciencemag.org states, the primary factor causing this deoxygenation is rising ocean temperatures. All one needs to do in order to see the dramatic rise in ocean heat content over the past century is to examine data provided by the National Oceanic and Atmospheric Administration (NOAA).
This data is available to the public and can be accessed by anyone willing to investigate the matter for themselves.
The visual graphic of oceanic heat content appears minimal up until the mid-twentieth century. And in the past twenty years or so, it soars off the charts.
Dead zones also caused by pollution
Another factor noted in the paper involves changing nutrient concentrations caused by pollution such as sewage runoff.
The paper states that “In the longer term, these conditions are unsustainable and may result in ecosystem collapses, which ultimately will cause societal and economic harm.”
There’s no question that ongoing “biological annihilation” (as a different scientific paper published in 2017 put it) will have dramatic effects on the global economy as a whole.
Deoxygenation of oceans will have the most immediate and obvious impact upon coastal communities that rely upon tourism. Taxi drivers, restaurants, and hotels may suffer under the pressures of fewer tourists visiting areas plagued by deoxygenation.
Still, The Independent reports that something can be done. According to one of the study’s authors, Dr. Lisa Levin, a biological oceanographer at Scripps Institution of Oceanography, utilizing improved sewage treatment has helped to raise oxygen levels off the shores of the Eastern US. She doesn’t mention how rising ocean heat content can be improved. Strange, considering the paper cites this as being the primary factor driving ocean deoxygenation.
In short, a hotter, more acidic, deoxygenated ocean leads to an increase in ocean dead zones. An increase in ocean dead zones leads to less marine biodiversity, decreased economic activity related to tourism, and a planet less hospitable to life overall.
