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Researchers studying 17 different activities ranging from fishing to pollution compiled a new map showing how and where people have impacted the seas.
The map was released at the annual meeting of the American Association for the Advancement of Science in Boston and published in Friday's edition of the journal Science.
"Our results show that when these and other individual impacts are summed up, the big picture looks much worse than I imagine most people expected. It was certainly a surprise to me," said lead author Ben Halpern, an assistant research scientist at the National Center for Ecological Analysis and Synthesis at the University of California, Santa Barbara.
The areas most affected include the North Sea, the South and East China Seas, Caribbean Sea, the east coast of North America, the Mediterranean Sea, the Red Sea, the Persian Gulf, the Bering Sea and parts of the western Pacific, the study found. It said the least affected areas are near the poles.
However, the researchers said it is likely that human activities will affect polar regions more and more as climate change warms those areas.
Damage includes reductions in fish and sea animals as well as problems for coral reefs, seagrass beds, mangroves, rocky reefs and shelves and seamounts.
"There were two things we didn't anticipate," Halpern said in a telephone interview. "Every single spot in the oceans was affected by at least one human activity ... we figured there'd be places people just hadn't gotten to yet."
And "more than 40 percent is impacted by multiple different activities," he added. "The oceans are not in good shape."
Yet Halpern did find room for hope.
"There are some areas in fairly good condition. They are small and scattered, but have fairly low impact," he said. "That suggests that with effort from all of us, we can try to protect these patches and use them as a guideline for what we'd like the rest of the ocean to start looking like."
The 19-member research team mapped the varying impacts on the oceans and then through overlays of the maps they were able to compile which areas were most affected.
"This research is a critically needed synthesis of the impact of human activity on ocean ecosystems," David Garrison, biological oceanography program director at the National Science Foundation, said in a statement.
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 Impacts studied by the researchers included the effects of structures such as oil rigs, commercial shipping, species invasion, climate-change impacts including acidification, ultraviolet radiation and sea temperature, various types of fishing and several types of human-related pollution.
In a separate paper in the same issue of Science, researchers reported that oxygen levels in some of the shallow waters along the coast of Oregon dropped to virtually nothing for the first time ever in 2006.
The research team led by Francis Chan at Oregon State University said the cause of this change is not yet completely clear, but the findings show how quickly the distribution of oxygen can change.
In the region upwelling currents bring nutrient-rich but oxygen-poor water onto shallow areas where the nutrients support an abundance of life, but they are also vulnerable to the risk of low-oxygen events.
Halpern's study was funded by the National Center for Ecological Analysis and Synthesis, the National Science Foundation and the David and Lucille Packard Foundation.
Chan's research was funded by the David and Lucille Packard Foundation, the Gordon and Betty Moore Foundation, the National Science Foundation and the National Oceanic and Atmospheric Administration.
In Congress on Thursday, the House voted 352-49 to approve $454 million over the next seven years for two ocean exploration programs at the National Oceanic and Atmospheric Administration. Rep. Jim Saxton, R-N.J., the bill's sponsor, said it would coordinate efforts to study marine ecosystems, organisms and geology.
About 95 percent of the ocean floor remains unexplored, he said. "This vast area teems with undiscovered species and natural and cultural resources."
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[Associated
Press; By RANDOLPH E. SCHMID]
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