What is a marine dead zone? Also known as hypoxia, it is an
area in the ocean with such low oxygen concentration that animal life
suffocates and dies, hence the name dead zone. “Hypoxic zones can occur
naturally, but scientists are concerned about the areas created or enhanced by
human activity (NOAA).
There are many physical, chemical, and biological factors that
combine to create dead zones, but nutrient pollution is the primary cause of
those zones created by humans. Excess nutrients that run off land or are piped
as wastewater into rivers and coasts can stimulate an overgrowth of algae,
which then sinks and decomposes in the water. The decomposition process
consumes oxygen and depletes the supply available to healthy marine life” [NOAA
https://oceanservice.noaa.gov/facts/deadzone.html
].
Scientists predict that the Gulf dead zone will cover about
6,620 square miles of the bottom of the continental shelf off Louisiana and
Texas. The Gulf dead zone is the second largest HUMAN CAUSED one in the world.
Science daily reported that “Efforts to reduce the nitrate loading have not yet
demonstrated success at the watershed scale”
[https://www.sciencedaily.com/releases/2018/06/180607120724.htm
]. The dead zone is present all year long, but is most prevalent during spring
and summer, citing nutrients from the Mississippi River watershed contribute to
the problem.
To read the full report go to Science
Daily story here.
Map showing distribution of
bottom-water dissolved oxygen from July 28 to August 3, west of the Mississippi
River delta. Black lined areas — areas in red to deep red — have very little
dissolved oxygen. (Data: Nancy Rabalais, LUMCON; R Eugene Turner, LSU. Credit:
NOAA)
