Antarctic Penguins Thrive In Ocean 'Oases'

Elvia Thompson
Headquarters, Washington                   October 7, 2003
(Phone: 202/358-1696)

Krishna Ramanujan 
Goddard Space Flight Center, Greenbelt, Md.
(Phone: 607/273-2561)

Mark Shwartz
Stanford News Service, Calif.
(Phone: 650/723-9296)

RELEASE: 03-315

ANTARCTIC PENGUINS THRIVE IN OCEAN  "OASES"

     NASA satellite data was used for the first time to 
analyze the biology of hot spots along the coast of 
Antarctica. The biological oases are open waters, called 
polynyas, where blooming plankton support the local food 
chain.

The research found a strong association between the well being 
of Adelie Penguin populations in the Antarctic and the 
productivity of plankton in the polynyas. Polynyas are areas 
of open water or reduced ice cover, where one might expect sea 
ice. They are usually created by strong winds that blow ice 
away from the coast leaving open areas, or by gaps appearing 
on the ocean's surface, when flowing ice gets blocked by an 
impediment, like an ice shelf.

The Antarctic waters are rich in nutrients. The lack of ice, 
combined with shallow coastal waters, provides the top layers 
of the ocean with added sunlight, so polynyas offer ideal 
conditions for phytoplankton blooms. Because the ice around 
polynyas is thin in the early spring when the long Austral day 
begins, they are the first areas to get strong sunlight. The 
open waters retain more heat, further thinning ice cover and 
leading to early, intense, and short-lived plankton blooms. 
These blooms feed krill, a tiny, shrimp-like animal, which in 
turn are eaten by Adelie Penguins, seabirds, seals, whales, 
and other animals.

Although relatively small in area, coastal polynyas play a 
disproportionately important role in many physical and 
biological processes in Polar Regions. In eastern Antarctica, 
more than 90 percent of all Adelie Penguin colonies live next 
to coastal polynyas. Polynya productivity explains, to a great 
extent, the increase and decrease in penguin population.

"It's the first time anyone has ever looked comprehensively at 
the biology of the polynyas," said Kevin Arrigo, assistant 
professor of Geophysics at Stanford University, Stanford, 
Calif. "No one had any idea how tightly coupled the penguin 
populations would be to the productivity of these polynyas. 
Any changes in production within these polynyas are likely to 
lead to dramatic changes in the populations of penguins and 
other large organisms," Arrigo said.

The study, which appeared in a recent issue of the Journal of 
Geophysical Research, used satellite-based estimates to look 
at interannual changes in polynya locations and sizes; 
abundance of microscopic free-floating marine plants called 
phytoplankton, which are the base of the polar ocean food 
chain; and the rate at which phytoplankton populations thrive. 
Covering five annual cycles from 1997 to 2002, 37 coastal 
polynya systems were studied.

The largest polynya studied was located in the Ross Sea 
(396,500 square kilometers or 153,100 square miles; almost the 
size of California). The smallest was located in the West 
Lazarev Sea (1,040 square kilometers or 401.5 square miles). 
Most polynyas, at their maximum area in February, were less 
than 20,000 square kilometers (7,722 square miles).

Data from NASA's Sea-viewing Wide Field-of-view Sensor 
(SeaWiFS) and NOAA's Advanced Very High Resolution Radiometer 
(AVHRR) provided weekly measurements of chlorophyll and 
temperature that were used in a computer model to estimate 
phytoplankton productivity. The researchers found, taken 
together, the Ross Sea, Ronne Ice Shelf, Prydz Bay, and 
Amundsen Sea polynyas were responsible for more than 75 
percent of total plankton production.

The researchers were surprised to find how closely connected 
the Adelie Penguins were to the productivity of their local 
polynyas. The more productive polynyas supported larger 
penguin populations. The more abundant krill fed more 
penguins, and the birds had shorter distances to go to forage, 
which reduced exposure to predators and other dangers.

The NASA Oceanography Program, the National Science 
Foundation, and the U.S. Department of Energy funded this 
research. NASA's Earth Science Enterprise is dedicated to 
understanding the Earth as an integrated system and applying 
Earth System Science to improve prediction of climate, 
weather, and natural hazards using the unique vantage point of 
space.

For information about the research and images on the Internet, 
visit:

http://www.gsfc.nasa.gov/topstory/2003/0930penguins.html

For information about Adelie Penguins, on the Internet, visit:

http://www.aad.gov.au/default.asp?casid=1654

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