In the past 50 years, the amount of water in the open ocean with zero oxygen has increased more than four times. In coastal water bodies, including the river mouth and seas, low-oxygen sites have increased more than 10 times since 1950. Scientists expect oxygen to continue dropping even outside these zones as the Earth warms. To stop the decline, the world needs to control in both climate change and nutrient pollution.
Oxygen is a must to life in the oceans. The drop in ocean oxygen is among the most serious effects of human activities on the Earth’s environment.
This is the first time for the scientists to take such a deep look at the causes, consequences and solutions to low oxygen worldwide, in both the open ocean and in coastal waters. About half of the oxygen on Earth comes from the ocean. However, combined effects of nutrient loading and climate change are greatly increasing the number and size of “dead zones” in the open ocean and coastal waters, where oxygen is too low to support most sea life.
In areas traditionally called “dead zones”, like those in Chesapeake Bay and the Gulf of Mexico, oxygen drops to levels so low that many animals have trouble in breathing and die. As fish run away from these zones, their living areas become smaller and smaller. But the problem goes far beyond “dead zones”. Even smaller oxygen drops can hold up the growth in animals, reproduction and lead to disease or even death. Low oxygen also can cause the release of dangerous chemicals. While some animals can thrive in dead zones, overall biodiversity falls.
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