Explanation:

'Dead Zone'
The Bay of Bengal (BoB) hosts a 'dead zone' of around 60,000 square kilometers almost devoid of oxygen, a new multi-national study has shown.

• Less oxygen dissolved in the water is often referred to as a “dead zone” because most marine life either dies, or, if they are mobile such as fish, leave the area.
• 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.
• Dead zones occur in many areas of the country, particularly along the East Coast, the Gulf of Mexico, and the Great Lakes, but there is no part of the country or the world that is immune. The second largest dead zone in the world is located in the U.S., in the northern Gulf of Mexico.
• Until now, there have been only three major identified dead zones – two in the eastern tropical Pacific (off Peru/Chile and Mexico) and one in the Arabian Sea. Bay of Bengal is the new in the list.