Many environmental groups are warning that oceans of the world are in great danger. In the past 50 years, the number of water with zero oxygen(氧气) in the open ocean has increased more than four times. In the near coast water bodies, including the river mouth and seas, low-oxygen areas have increased more than 10 times since 1950.Scientists discover that oxygen continues dropping ever outside these zones as the Earth warms. To stop the drop, the world needs to control in both climate change and nutrient(养分) 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, results and solutions to low oxygen worldwide, in both the open ocean and the near coast waters. About half of the oxygen on Earth comes from the ocean. However, mixed effects of nutrient loading and climate change are greatly increasing the number and size of "dead zones" in the open ocean and the near coast waters, where oxygen is too low to support most sea life.
In the 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 fishes 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 and lead to disease or even death. Low oxygen also can cause the release of dangerous chemicals. Although a few animals can grow well in dead zones, overall biodiversity(多样性)falls.
