A report by a panel of scientists has suggested that climate change is rapidly transforming the world's oceans by increasing the temperature and acidity of seawater, and altering atmospheric and oceanic circulation.
"The world's oceans are undergoing profound physical, chemical and biological changes whose impacts are just beginning to be felt," said Jane Lubchenco, the Wayne and Gladys Valley Chair of Marine Biology at Oregon State University, who moderated the panel.
According to panelist Gretchen Hofmann, a molecular physiologist at the University of California, Santa Barbara, "Ocean ecosystems are facing new stresses and new combinations of stress."
"The water is warmer, circulation patterns are changing in unpredictable ways, and oceans are becoming acidic," he added.
Rising greenhouse gas emissions are already warming the world's oceans and providing yet a new threat to coral reefs, which already are among the most threatened of all marine ecosystems.
"Even modest warming of a degree or two above normal maximum temperatures can cause a breakdown in the relationship between corals and their symbiotic algae, zooxanthellae," said Nancy Knowlton, a marine biologist with the Smithsonian Institution.
According to Knowlton, "We have already lost some 80 percent of the reef corals in the Caribbean over the last three decades, and losses in the Pacific Ocean also are widespread and severe."
"These reefs already are under threat to overfishing and local pollution and unless drastic action to reduce greenhouse gas emissions is taken soon, these reefs will cease to exist as we know them," she added.
"These same greenhouse gas emissions also are creating dramatic buildup of atmospheric carbon dioxide, which is rapidly making the world's oceans more acidic," said panelist Scott Doney of the Woods Hole Oceanographic Institution.
Current CO2 levels of 380 parts per million already are 30 percent higher than pre-industrial values and many scientific models predict that those rates will triple by the end of the century under the usual scenarios.
"Ocean acidification harms plants and animals that form shells from calcium carbonate," said Doney.
"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," he explained.
For fighting the adverse impacts of global warming on the oceans, the panelists have called for greater investment in ocean observing systems that would allow scientists to better measure changing in the ocean ecosystem, including large-scale circulation and coastal upwelling systems around the world.