Ships return to the southern ocean to enhance understanding of food chain

May 07, 2002

Two National Science Foundation (NSF) research vessels have sailed from Chile toward the wintry waters off the Antarctic Peninsula, where they will examine the interlocking links of a food chain. Tiny shrimp-like animals called krill anchor that food chain, feeding on microscopic plants and animals and forming the basis of a living web that supports some of Earth's largest marine mammals.

The R.V. Laurence M. Gould and the R.V. Nathaniel B. Palmer will serve as the home to about 100 scientists and support personnel for six weeks as they cruise the waters of Marguerite Bay on the Western side of the Peninsula in the second datagathering cruise of the Southern Ocean Global Ecosystem Dynamics (SO GLOBEC) program.

Eileen Hofmann of Old Dominion University, the project's chief scientist, noted that the project last year gathered the most comprehensive set of data currently available on a host of factors such as the distribution and abundance of krill in the Southern Ocean. Next year, the data gathered last season and this will be analyzed for trends and patterns that will allow scientists to grasp how environmental conditions affect life in one of the world's most biologically productive bodies of water.

In a key feature of this year's SO GLOBEC cruise, the ships will return to an area that was studied intensively last spring. This will give scientists an important comparison of conditions over time, said Hofmann.

"Repeating the cruise in the same area this year will tell us quite a bit about year-to-year variability," she said. "We already know from satellite data that the sea ice is more extensive this year, and that's good, because one of the projects' science objectives is to test the extent to which over-wintering krill are dependent on the extent and position of the sea ice."

The Southern Ocean's vast productivity depends on the small but enormously abundant Antarctic krill. Krill feed on microscopic plants and animals and, in turn, are fed upon by whales and fish. Seals, penguins and other sea birds eat the fish. Hofmann said that using data collected last year on where krill are most abundant would allow the scientists to focus their efforts on the most productive areas of study this season.

"We're a lot smarter this year. We know a lot more now about where we might expect to find seals, for example," she said. "Last year we were able to identify what people were calling "hot spots" or places where krill aggregate. There were also lots of whales, seals and birds there. The first time around we had to find these hot spots. This time, we're going to spend more time using those areas for specific studies."

Scientists on this year's cruise, while hoping eventually to grasp the "big picture" of Southern Ocean ecology, also have added measurements to look at the mixing of temperature and salinity in the water at centimeter and millimeter scales. Such mixing occurs on a far larger scale in more temperate waters, another factor that may make the Southern Ocean unique. "We think that's the dominant mixing process in this area," Hofmann said.

At the other extreme of size, biologists of the International Whaling Commission will examine these mammals to see how actions at the microscopic scale eventually affect the Southern Ocean's dominant predators.

As they did last year, the Palmer and the Gould will work together to sample different aspects of the survey area. The Palmer will conduct a wide oceanic survey at points along a fixed grid and will collect data along the grid lines. The Gould will spend four to five days at each of five stations in strategic locations.
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Media contact:
Peter West 703-292-8070; pwest@nsf.gov

National Science Foundation

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