Low-oxygen zones in oceans spreading by Zuzana Zelenakova

Low-oxygen zones in oceans that are normally found in deeper water are spreading to the coastal areas. Scientists are worried, because such a development threatens offshore sea animals and entire ecosystems. Marine species living in these areas are forced either to die or move somewhere else. The problem is most visible in the area of the United States´ Pacific Northwest coast, however, scientists all over the world have been noticing the same phenomenon for quite some time. "The depletion of oxygen levels in all three oceans is striking," said Gregory Johnson , an oceanographer with the National Oceanic and Atmospheric Administration in Seattle , referring to the Pac! ific, Atlantic and Indian oceans. According to scientists, low-oxygen areas are spreading quite quickly and might decline by about one-third in next 50 years. Lisa Levin of the Scripps Institution of Oceanography in La Jolla, California, says that larger animals such as marlin, tuna, or sailfish will be forced to relocate into shallower water, where they will become a lot easier prey. "That may be good for fishermen, but it also makes it a lot easier for fishermen to fish these species out of the ocean,” she says. Many experts believe the main reason behind this trend is current climate-change, or global warming to be more precise. The more greenhouse gases oceans absorb, the more acidic they become. "If the Earth continues to warm, the expectation is we will have lower and lower oxygen levels," said Francis Chan , a senior marine researcher at Oregon State University. He further explains that warm waters floating above deeper and colder currents make it more diffic! ult for cold water to rise and mix with the oxygenated surface! level. In addition, the fact is warm water contains less oxygen. Some species simply move away from the low-oxygen waters, "But for those whose stress response is to hunker down and wait, they will die," says Chan.

related story (sgx16703): http://news.yahoo.com/s/mcclatchy/20100307/sc_mcclatchy/3444...

by Zuzana Zelenakova for SigEx Ventures (http://sigexventures.com)

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