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24. Dead zones

• Dead zones are large areas in the ocean that have low oxygen concentration.

• The marine life in these areas mostly suffocates and dies or if they are mobile like the fish then,
they leave the area.

• Though at many times, dead zones occur naturally, scientists are also of the opinion that they are
created due to increased human activity.

• The main cause of the zones created by humans is nutrient pollution. Excess nutrients (nitrogen and
phosphorus) can result in the overgrowth of algae, which later decomposes in the water consuming
excess oxygen, depleting the supply available for the marine life.

Dead zones can be found in virtually every oceanic body, the largest encompassing almost the whole
bottom of the Baltic Sea.

Another large dead zone is located in the Gulf of Mexico. Other dead zones occur off the western coasts
of North and South America and off the coast of Namibia and western coast of India.

Global warming triggered by climate change is predicted to lead to an expansion of these dead zones.
However, it is not certain whether the climate change would lead to the removal of the last traces of
oxygen from the bay as well.