Monday, March 8, 2010

Oxygen Levels in Earth's Ocean Getting Lower - Marine Life Dying

Oxygen levels in the Earth's oceans are apparently getting lower. Years after year, scientists have seen how certain deep areas of the seas, which normally have low oxygen, are getting bigger and moving into areas that are not known to suffer from hypoxia (lack of oxygen). The change is very evident in the Pacific Northwest coast. Already, in areas off the Washington and Oregon coast, an almost complete lack of oxygen in the water has left marine life, mostly crabs, dead with their carcasses littering the ocean floor. Such mass kills include fish in other areas of the world. Scientists believe the changes are part of the global climate change.

The "dead" hypoxic water in oceans usually lie deep and far from the continental shelf. But now, they are moving closer to shore and getting nearer the surface, where marine plants and animals typically thrive. Oceanographer Gregory Johnson, of the National Oceanic and Atmospheric Administration (NOAA) in Seattle, describes the depletion of oxygen levels in the oceans as striking. Scientists estimate the decline of oxygen in certain areas of the world to be at least one-third of what used to be the levels used to be 50 years ago. 

Marine scientist Francis Chan says the Earth's oceans can expect to experience more depletion if the planet continues to warm up. Warmer waters ted to stay put near the surface and prevents the usual temperature-difference circulation of water from the deep ocean to the surface. It's like water in an aquarium that's not agitated by bubbles. The less agitation, the less oxygen is dissolved in the water. In the opinion of some people, not much can be done about the depletion since the affected areas are too widespread and there's no control over the marine life that can come into contact with them. 

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