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In This Issue

• Results Revealed from Decade-Long Quest to Tally All Marine Life
• Arctic Sea Ice in "Death Spiral"
• Groundwater Use Increasing Sea Level Rise

Science in the News

Results Revealed from Decade-Long Quest to Tally All Marine Life

South of Easter Island, researchers studying hydrothermal vents discovered a species of crab so unusual it warranted classification in an entirely new family. The discovery was just one of many found during the decade-long Census of Marine Life. A. Fifis Ifremer 2006

Researchers have identified nearly 20,000 additional species as a result of the decade-long Census of Marine Life, which concluded Monday. The total number of species now known to live in the ocean is nearly 250,000, but scientists say that may only be a fraction of the total that remains to be discovered.

The team of 2,700 researchers from 80 nations released their final findings on October 4 after a study that brought them out to sea for 9,000 days during more than 540 expeditions. Initiated in 2000 by Fred Grassle of Rutgers University and Jesse Ausubel of the Alfred P. Sloan Foundation, the Census grew to involve more than ten times its original 250 collaborators and resulted in the publication of more than 2,600 scientific papers—almost one every 1.5 days. The initiative increased the estimate of known marine species from approximately 230,000 to nearly 250,000, provided images of creatures never seen before and mapped areas of high and low diversity of marine life.

Among the team’s findings was that coastal species showed maximum diversity in the tropical Western Pacific, whereas high diversity of species frequenting the open ocean peaked in the mid-latitudes in all ocean areas. On the seafloor, the quantity of life peaks toward polar regions, along continental margins where cool currents well up toward the surface, and where equatorial currents diverge. They also found that by weight, up to 90 percent of marine life is microbial, with the weight of Earth’s marine microbes equaling about 35 elephants for every living person. The Census also documented decline. For example, by analyzing indirect observations from oceangoing vessels since 1899, Census researchers discovered that the food-producing phytoplankton near the surface has declined around the world.

“Setting out to draw baselines of the diversity, distribution, and abundance of species, the first Census of Marine Life documented a changing ocean, richer in diversity, more connected through distribution and movements, more impacted by humans, and yet less explored than we had known,” said Ausubel in a press release.

“The Census enlarged the known world. Life astonished us everywhere we looked,” added Miriam Sybuet, vice-chair of the Census' Scientific Steering Committee. “In the deep sea we found luxuriant communities despite extreme conditions. The discoveries of new species and habitats both advanced science and inspired artists with their extraordinary beauty.”

The Census revealed what remained to be discovered almost as much as it provided new information on species diversity and distribution. While they upped the total of known species to 250,000, Census scientists estimate that the ocean may play host to as many as a million species in total, leaving three-quarters as yet undiscovered. For more than 20 percent of the ocean’s volume, the Census database still has no records at all, and for vast areas very few. As a consequence, researchers are already discussing the possibility of launching a second census.

For Further Information: Full information about the Census of Marine Life is available at www.coml.org. A summary of the Census findings may be downloaded at http://dl.dropbox.com/u/3960397/FINAL%20highlights%20summary.pdf.

Science Briefs

Arctic Sea Ice in "Death Spiral"

The Arctic sea ice minimum in 2010 was the third-lowest on record. The white area shows the extent of sea ice in the Arctic on September 19 this year. The orange line delineates the average extent from 1979 to 2000. National Snow and Ice Data Center

Sea ice in the Arctic Ocean is in a “death spiral,” says Mark Serreze, director of the U.S. National Snow and Ice Data Center (NSIDC), following NSIDC's publication of data showing that in September of this year Arctic sea ice cover reached the third-lowest level ever recorded.

NSIDC announced that Arctic sea ice cover reached its lowest extent of the year on September 19, at which point it began to expand with the onset of winter. This year's “sea ice minimum” measured 1.78 million square miles (4.6 million square kilometers), 193,000 square miles (500,000 square kilometers) below 2009, the previous third-lowest extent.

Arctic Ocean sea ice extent has been declining on average since NSIDC began using satellite imagery to monitor it in 1979. For the first 12 years, the downward trend was relatively steady. However, in 2002, sea ice extent declined precipitously, recovered only marginally in 2003 and 2004, and fell to a new low in 2005. In 2007, it fell sharply again, to 1.65 million square miles (4.28 million square kilometers), 23 percent lower than 2005. It recovered slightly in 2008 and 2009 before falling again this year.

The biggest difference between 2010 and the record low extent of 2007 is that far more sea ice was in the East Siberian Sea this past year than three years ago. However, in some areas of the Arctic Ocean—parts of the Beaufort Sea and particularly the East Greenland Sea, for example—sea ice levels were actually lower than in 2007.

According to NSIDC, of even greater long-term concern than the extent is the age and thickness of the ice that remains. In 1987, 57 percent of the ice was at least five years old, and a quarter of that ice was at least nine years old. By 2007, only 7 percent was at least five years old, and in 2009, only 19 percent was more than two years old, the least amount of this age in the satellite record. Younger ice is thinner, which requires less energy to melt in the summer and leaves a less substantial base for winter ice growth. Therefore Arctic sea ice may reach a tipping point at which summer sea ice cover may melt entirely.

For Further Information: NSIDC's most recent announcements on Arctic sea ice are available at http://nsidc.org/arcticseaicenews/. A full analysis of the 2010 sea ice minimum will be posted in early October.

Groundwater Use Increasing Sea Level Rise

Saltwater inundation from rising sea levels threatens many coastal freshwater marshes, such as this one at Alligator River in North Carolina. James Shelton/Marine Photobank

In recent decades, the rate at which humans worldwide are pumping dry the vast underground stores of water that billions depend on has more than doubled, say scientists who have conducted an unusual, global assessment of groundwater use. People are drawing so much water from below that they are adding enough of it to the ocean (mainly by evaporation, then precipitation) to account for about 25 percent of the annual sea level rise across the planet, the researchers find.

In a paper to be published in an upcoming edition of the journal Geophysical Research Letters, Marc Bierkens of Utrecht University and colleagues found that the rate at which global groundwater reserves are shrinking has more than doubled between 1960 and 2000, increasing the amount lost from 30 to 68 cubic miles (126 to 283 cubic kilometers) of water per year. Because the total amount of groundwater in the world is unknown, it’s hard to say how fast the global supply would vanish at this rate. But if water were siphoned as rapidly from the Great Lakes, they would go bone-dry in around 80 years.

The highest rates of depletion occur in some of the world’s major agricultural centers, including northwest India, northeastern China, northeast Pakistan, California’s central valley, and the midwestern United States. Most water extracted from underground stocks ends up in the ocean, the researchers note. The team estimates the contribution of groundwater depletion to sea level rise to be 0.03 inches (0.8 millimeters) per year, which is about a quarter of the current total rate of sea level rise of 0.12 inches (3.1 millimeters) per year. That’s approximately equivalent to the amount sea-level rise caused by the melting of glaciers and icecaps outside of Greenland and Antarctica, and it exceeds or falls into the high end of previous estimates of groundwater depletion’s contribution to sea level rise, the researchers add.

Source: Bierkens, M.F.P. et al. In press. A worldwide view of groundwater depletion. Geophysical Research Letters.

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