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Why are oceans at risk from global warming? mongabay.com February 17, 2008
The vastness of our oceans may have engendered a sense of complacency about potential impacts from global climate change, said Jane Lubchenco, a marine biologist at Oregon State University and moderator of the panel. The worlds oceans are undergoing profound physical, chemical and biological changes whose impacts are just beginning to be felt. Ocean ecosystems are facing new stresses and new combinations of stress, said Gretchen Hofmann, a molecular physiologist at the University of California, Santa Barbara. The water is warmer, circulation patterns are changing in unpredictable ways, and oceans are becoming acidic. Particularly at risk are coral reefs. Rising temperatures increase the risk of coral bleaching, while elevated carbon dioxide concentrations increase ocean acidity, making it more difficult for corals to form their calcium carbonate structural basis. Coral bleaching occurs when symbiotic algae that provide corals with sustenance are expelled, leaving corals more susceptible to disease and death.
Increasing ocean acidity is also threatening other organisms, including the base of the ocean foot chain: plankton. Ocean acidification harms plants and animals that form shells from calcium carbonate, said Scott Doney of the Woods Hole Oceanographic Institution. Calcifying organisms include not just corals, but many plankton, pteropods (marine snails), clams and oysters, and lobsters. Many of these organisms provide critical food sources or habitats for other organisms and the impact of acidification on food webs and higher trophic levels is not well understood." Newly emerging evidence suggests that larval and juvenile fish may also be susceptible to changes in ocean pH levels. Ocean acidification is rapidly becoming a real problem. The panelists said that changes in ocean circulation are also having an impact. Jack Barth, an oceanographer at Oregon State University, spoke about hypoxia events that have killed marine life in the Pacific Northwest since 2000. One of the things we've observed is how wind patterns have changed and greatly affected upwelling, Barth said. Two decades ago, the winds would last for three or four days, and then subside. Now they persist for 20 to 40 days before settling down. This creates significant impacts on upwelling and biological productivity, but these impacts can swing wildly from one extreme to another and have been difficult to predict. This article is based on a news release from Oregon State University
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