Seabird researchers discover new penguin colony on Charcot Island
Posted June 18, 2010
The mission: Find out as much as possible about the ecology of an Adélie penguin colony that boasts more than 60,000 breeding pairs. And do it in five days.
That’s the task that Kristen Gorman and her field teammate Shawn Farry faced in January when the ARSV Laurence M. Gould dropped them off at Avian Island, just south of the Antarctic Circle on the western side of the Antarctic Peninsula.
It’s been a regular stop on the Palmer Longer Term Ecological Research (PAL LTER) cruise each year since 1999 under the program’s seabird component led by Bill Fraser with the Polar Oceans Research Group in Montana.
The idea is for the two biologists to replicate the same work done by Fraser’s main field team, which tracks and monitors penguins and other seabirds around Palmer Station, about 400 kilometers to the north.
“They go nonstop while they’re there. It’s a vignette of Palmer work, only picked up and plunked down on Avian and done in five days,” said Donna Patterson-Fraser, one of the field team members working out of Palmer Station on Anvers Island. Their fieldwork lasts for months, beginning around October when the Adélies and other birds return to the islands around the station to breed and raise their young.
The birders, as everyone at the station calls them, work nearly every day, traveling by small inflatable boats to nearly 20 islands, most within a few kilometers of Palmer. The daily tasks vary, but they include censusing the different bird populations, weighing and measuring chicks, and sampling the diet of the penguins.
The Avian Island visit by the Gould, as part of a 28-day ocean voyage, coincides with the time that the chicks are maturing into adults. “We’re comparing the health of the chicks at both ends of the spectrum,” Patterson-Fraser said.
Around Palmer Station, where the climate is rapidly warming, the Adélie penguins are dying out. The penguins and their primary prey, krill, are both under stress, especially as their preferred habitat, sea ice, disappears from the region.
On the other hand, the ecosystem around Avian Island is still relatively healthy farther south. Chicks on Avian average about 300 grams heavier than their northern counterparts do.
“It’s a totally incredible place,” Gorman said of Avian Island, home also to southern giant petrels and blue-eyed shags. “It’s probably one of the most important breeding colonies for Adélie penguins along the peninsula region.”
A slim and athletic thirty-something, Gorman is working on her PhD in Antarctica. This is her fifth trip to the Ice in as many years. Her specific research involves comparing the breeding success of the Adélies against their subantarctic cousins, gentoos and chinstraps, which have migrated onto some of the islands around Palmer Station.
She wants to know how breeding performance is related to nutrition and foraging — why those southern chicks are fatter. In addition to diet sampling — literally looking at a penguin’s last meal — she also collects tissue samples from the birds, eggs and nests for later lab analysis.
Scientists can look at the ratios of carbon and nitrogen stable isotopes from the organic samples and determine what else might be on the menu. In other words, you are what you eat: An animal absorbs the carbon and nitrogen isotopes that are stored in its food. That ratio of carbon and nitrogen isotopes remains a part of its tissues as long as it’s eating that particular food.
“We’re sort of able to combine body condition with the ecology of the animals,” Gorman said. “It gives us this nice contrast between breeding populations of penguins that are experiencing lower sea ice in the north to medium to higher sea ice conditions to the south.”
Such high-tech methods for diet reconstruction complement more hands-on techniques involving sediment traps placed under pebbly penguin nests. The trap, a wooden frame with a mesh screen, captures penguin guano all season. The researchers remove the traps and wash the gooey, poo-covered rocks, eventually sifting the material to find fish ear bones (otoliths), squid beaks and other evidence of diet.
“That’s one of our most favorite events,” Gorman said, laughing.
Gorman and Farry camp on Avian for five days, using a dilapidated Chilean hut, which got a new tarp roof this year, as shelter. Meanwhile, the scientists still aboard the Gould sail off to conduct their own experiments, looking at other parts of the polar food web and the physical and chemical properties of the ocean.
Some of their work directly supports the birders on Avian. For instance, a team from Rutgers University releases a robotic glider from an inflatable Zodiac, programmed to “fly” through the penguins’ foraging areas based on satellite tags placed on the birds. The gliders are capable of measuring ocean properties like temperature, salinity and fluorescence, which offer clues to the sort of conditions that exist where birds feed.
“That’s another way we have a nice interaction between the people on shore and the people on the boat,” noted Hugh Ducklow , principal investigator for the PAL LTER program and chief scientist for the 2010 cruise.
Said Gorman, “In terms of ocean properties where they are foraging, that’s a huge unknown. That’s where the glider comes in. It’s able to characterize those water masses quite well.”
Avian Island used to mark the farthest south for the PAL LTER program. Two years ago, the scientists extended the grid south 325 kilometers to Charcot Island, where summer sea ice still persists, unlike at the north end of their study grid. This sort of spatial trip back through time, moving north to south, offers a window into what conditions around Palmer were like before the PAL LTER program began in 1990. (Fraser’s seabird studies date back to 1975.)
Among their new discoveries, the scientists found a deep marine canyon near Charcot, similar to ones associated with penguin colonies at Avian Island and Anvers Island. Not too surprisingly, they found a small Adélie colony on the rocky, steep shores of Charcot.
“These penguin hotspots tend to be associated with this bathymetry that brings upwelling and nutrients to the region so that they have this predictable foraging area while they’re raising chicks on land,” Gorman said. “The fact that we find Adélies on Charcot isn’t that surprising.”
The birders have extended their monitoring program to the Charcot colony, a rough-looking bunch that appears to exist at the edge of even Adélie tolerance to sea ice. Sea ice is an important part of Adélie ecology, but too much sea ice means a long haul to open water for foraging. It appears the Charcot colony relies on a polynya, an area of open water in the sea ice, to forage.
The polynya itself is of interest to the PAL LTER team, as it’s also probably related to the deep canyon, which funnels not only nutrients but also slightly warmer deep ocean water onto the continental shelf, creating a sort of oasis in an ice-covered desert.
“It’s interesting because we don’t know much about it at all,” Gorman said of the Charcot region. “Everything that we’re learning is new.”
NSF-funded research in this story: Bill Fraser, Polar Oceans Research Group, Award No. 0823101 (includes Oscar Schofield, Deborah Steinberg and Hugh Ducklow).Return to main Palmer LTER story: Back in Time