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‘Dead zone’ in the Gulf of Mexico

Topics Covered:

Conservation, environmental pollution and degradation, environmental impact assessment.


‘Dead zone’ in the Gulf of Mexico


What to study?

For prelims and mains: location of Gulf of Mexico, about dead zones and eutrophication.


Context: Scientists from the National Oceanic and Atmospheric Administration and Louisiana State University have predicted that this spring’s record rainfall would produce one of the largest-ever “dead zones” in the Gulf of Mexico.


What are dead zones?

Unoxygenated “dead zones” appear in waterways wherever algae are overfed by runoff from human activities such as urbanization and agriculture – a phenomenon called eutrophication.


What caused dead zone in Gulf of Mexico?

The dead zone in the Gulf of Mexico, fueled by the nutrient-laden water spilling from the mouth of the Mississippi River, is the second-largest in the world.

It blooms every summer, when warming waters accelerate the metabolisms of microorganisms, and it is expected to get even worse as the climate continues to change.


The primary culprits in eutrophication appear to be excess nitrogen and phosphorus—from sources including fertilizer runoff and septic system effluent to atmospheric fallout from burning fossil fuels—which enter waterbodies and fuel the overgrowth of algae, which, in turn, reduces water quality and degrades estuarine and coastal ecosystems.


Effects of Eutrophication:

Eutrophication can also produce carbon dioxide, which lowers the PH of seawater (ocean acidification). This slows the growth of fish and shellfish, may prevent shell formation in bivalve mollusks, and reduces the catch of commercial and recreational fisheries, leading to smaller harvests and more expensive seafood.


What needs to be done?

  • Improvement of the purifying performance of waste water treatment plants, installing tertiary treatment systems to reduce nutrient concentrations;
  • implementation of effective filter ecosystems to remove nitrogen and phosphorus present in the run-off water (such as phyto-purification plants);
  • reduction of phosphorous in detergents;
  • rationalisation of agricultural techniques through proper planning of fertilisation and use of slow release fertilisers;
  • use of alternative practices in animal husbandry to limit the production of waste water.
  • oxygenation of water for restore the ecological conditions, reducing the negative effects of the eutrophic process, such as scarcity of oxygen and formation of toxic compounds deriving from the anaerobic metabolism;
  • chemical precipitation of phosphorous by the addition of iron or aluminium salts or calcium carbonate to the water, which give rise to the precipitation of the respective iron, aluminium or calcium orthophosphates, thereby reducing the negative effects related to the excessive presence of phosphorus in the sediments.


Sources: the Hindu.