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Lower oxygen levels in the oceans concern scientists

Posted on Monday, March 8th, 2010 at 5:56 pm by

It has been reported that scientists are worried about the growing number of low-oxygen zones in Oceans around the world. This is just another sign pointing at the changing global climate that threatens the oceans ecosystems.

In several spots off of US Pacific Northwest coast, low-oxygen zones have killed sea stars, eradicated a population of Dungeness crabs, and wreaked havoc on colonies of anemones, leading to an increase in potentially dangerous bacteria. Low Oxygen, known as hypoxia, is prevalent in the deep Atlantic, Pacific and Indian Oceans. Lately, however, this phenomenon seems to be spreading towards the surface. Oceanographer Gregory Johnson, of the National Oceanic and Atmospheric Administration says that “The depletion of oxygen levels in all three oceans is striking.”

Other studies (many of which we have already reported) point out that greenhouse gases are causing the oceans to become more acidic.

The cause for the increase in these low-oxygen levels is that as the surface temperature of the oceans rises, it acts as a cap, preventing the previously free circulation of deeper and shallower water. Water closer to the surface is much higher in oxygen, as it is constantly mixed with the air by waves. This hindered circulation prevents oxygen from traveling deeper into areas where it was previously prevalent. It was previously thought that low-oxygen zones were caused by pollution and agricultural runoff. It is now clear that although these circumstances play a roll in creating such zones, the atmospheric changes are a major contributing factor as well.

The long-term effects of these zones is unclear at this time, but scientists believe that bottom-dwelling species are at the greatest risk, since they are usually slow swimmers, and may be unable to quickly escape.

[Via Yahoo News]

Photograph by Felicia McCaulley

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