Tuesday, October 16, 2018 | ePaper

Suffocating oceans creating dead zones

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Life Desk :
Our seas and oceans are gasping for breath with very little oxygen in huge pockets of water.A new study by University of East Anglia researchers confirms the presence of a huge 'dead zone' in the Arabian sea near the Gulf of Oman, with minimally low oxygen level. If this is bad news, it gets worse. The dead zone is dramatically growing in size each year.
Another recent research conducted by scientists from the Global Ocean Oxygen Network (GO2NE) published in the Science says the number of water areas in the earth's ocean waters with zero oxygen has risen four times in the last 50 years because of nutrient pollution and climate change.
In coastal areas such as estuaries and seas, low-oxygen level areas have increased ten times since then. Scientists expect oxygen levels to drop further and even outside these zones due to global warming. 'Dead zones with very little or no oxygen are increasing in number and size all over the world due to pollution and global warming. These dead zones could release toxic gases into the atmosphere killing sea animals and affecting human lives.' The latest findings on our suffocating seas and oceans are alarming because the earth depends on the oceans for nearly half the oxygen required for survival.
"Oxygen is fundamental to life in the oceans," said Denise Breitburg, lead author and marine ecologist with the Smithsonian Environmental Research Center. "The decline in ocean oxygen ranks among the most serious effects of human activities on the Earth's environment."
In dead zones the oxygen levels are so low that marine life can suffocate and die.
Though they are naturally occurring, researches mapping these areas find their size is increasing due to fertilizer waste and sewage running into water bodies coupled with global warming and climate change.
"They are a disaster waiting to happen - made worse by climate change, as warmer waters hold less oxygen, and by fertilizer and sewage running off the land into the seas," says Dr Bastien Queste from UEA's School of Environmental Sciences who also led the study in the Arabian Sea.
 "Of course all fish, marine plants and other animals need oxygen, so they can't survive there. It's a real environmental problem, with dire consequences for humans too who rely on the oceans for food and employment, Dr. Queste adds.
Dead zones are just the tip of the iceberg. Lower oxygen levels can stunt growth in marine animals, affect reproduction and cause disease and death.
 Low oxygen levels can also increase the release of dangerous chemicals like nitrous oxide and hydrogen sulphide into the atmosphere. Nitrous oxide is a greenhouse gas which is about 300 times more powerful than carbon dioxide.
How does nutrient pollution affect human health?
Nutrient pollution is when too many nutrients such as nitrogen and phosphorus run into water bodies causing unnecessary and excessive growth of algae in water bodies. This process is known as eutrophication. Too much algae blocks the sunlight needed for other sea plants to grow. When the algae and sea plants die they decay, and in the process of decay, more oxygen in water is used up, leading to lower levels of oxygen dissolved in water. This, in turn kills fish, shrimps, crabs, oysters and other aquatic animals.
Nutrients can come from the natural weathering of rocks and soil but human-related nutrient pollution is becoming a matter of great concern. Factory effluents, run off from farming and waste water treatment facilities are increasing nutrient pollution and choking coastal waters rapidly in recent times.
Dead zone in the Arabian Sea
East Anglia researchers used underwater robots called Seagliders which collected data in areas in the Arabian Sea which were till now inaccessible for research due to piracy and geopolitical tensions in the Middle East.
The seagliders used were about the size of small human divers but could reach 1000 meters deep below to collect data, travel for over 8 months in this study and cover thousands of kilometers. They communicated via satellite to map the oxygen levels with underwater pictures and trace the ocean dynamics transporting oxygen from one region to another.
The scientists said they expected the presence of some oxygen in the area, but they found an area 'larger than Scotland' with almost no oxygen left.
How do we protect our seas and oceans?
Researchers from all over the world monitoring the health of our earth's waters suggest, people need to work on better septic systems and sanitation methods to protect human health and prevent run offs to keep pollution out of waters. Cutting down on fossil fuel emissions can help reduce air pollution.
Source: Medindia

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