Report: Oceans' deteriorating health nearing 'irreversible' `

A sobering new report warns that oceans face a "fundamental and irreversible ecological transformation" not seen in millions of years as greenhouse gases and climate change already have affected temperature, acidity, sea and oxygen levels, the food chain and possibly major currents that could alter global weather.

The report, in Science magazine, doesn't break a lot of new ground, but it brings together dozens of studies that collectively paint a dismal picture of deteriorating ocean health.

"This is further evidence we are well on our way to the next great extinction event," said Ove Hoegh-Guldberg, director of the Global Change Institute at the University of Queensland in Australia and a co-author of the report.

John Bruno, an associate professor of marine sciences at the University of North Carolina at Chapel Hill and the report's other co-author, isn't quite as alarmist, but he's equally concerned.

"We are becoming increasingly certain that the world's marine ecosystems are reaching tipping points," Bruno said, adding, "We really have no power or model to foresee" the impact.

The oceans, which cover 71 percent of the Earth's surface, have played a dominant role in regulating the planet's climate. However, even as the understanding of what's happening to terrestrial ecosystems as a result of climate change has grown, studies of marine ecosystems have lagged, the report says. The oceans are acting as a heat sink for rising temperatures and have absorbed about one-third of the carbon dioxide produced by human activities.

Among other things, the report notes:

The average temperature of the upper level of the oceans has increased more than 1 degree Fahrenheit over the past 100 years, and global ocean surface temperatures in January were the second-warmest ever recorded for that month.

Though the increase in acidity is slight, it represents a "major departure" from the geochemical conditions that have existed in the oceans for hundreds of thousands, if not millions, of years.

Nutrient-poor "ocean deserts" in the Pacific and Atlantic oceans grew by 15 percent, or roughly 2.5 million square miles, from 1998 to 2006.

Oxygen concentrations have been dropping off the Northwest U.S. coast and the coast of southern Africa, where dead zones are appearing regularly. There is paleontological evidence that declining oxygen levels in the oceans played a major role in at least four or five mass extinctions. Around the globe, the number of dead zones in the ocean are growing. These oxygen-depleted coastal areas are caused by fertilizer and industrial run-off, pollution, sewage and storm water drainage. Once the oxygen has been taken out of the water, nothing can live in it.

Since the early 1980s, the production of phytoplankton, a crucial creature at the lower end of the food chain, has declined 6 percent, with 70 percent of the decline found in the northern parts of the oceans. Scientists also have found that phytoplankton are becoming smaller.

Source:
Silicon Valley Mercury News, "Report: Oceans' deteriorating health nearing 'irreversible' `", accessed July 5, 2010