|
By Peter Rejcek
There’s an old saying: You are what you eat. But
the krill-based diet of penguins breeding and living on
King George Island off the northern end of the Antarctic
Peninsula first tipped scientists off that food could
provide an altogether different insight.
“It was the penguins that actually keyed us into
to the global change scenario that has become the leading
hypothesis about climate change in the peninsula region,”
explained Wayne Trivelpiece , a scientist with the National
Oceanic and Atmospheric Administration (NOAA) National
Marine Fisheries Service whose research also receives
support from the National Science Foundation (NSF) .
Trivelpiece, along with his wife and co-principal investigator,
Susan Trivelpiece , has compiled more than 30 years of
continuous data on the three types of penguins from a
seabird research program at King George Island —
Adélies, chinstraps and gentoos. During that time,
atmospheric temperatures in the peninsula region have
risen faster than anywhere on the planet, particularly
in the winter, where the average has increased by 5 degrees
Celsius.
“Studying all three [penguins] at once has given
us some real insights into just what happens when we come
across some major changes in environmental features and
climate, which has certainly happened there,” Wayne
Trivelpiece said.
Krill are shrimplike crustaceans that penguins, seals
and other marine denizens feed on. Krill rely on sea ice
in the winter as a habitat, grazing on algae that form
underneath the ice. But the increasing temperatures have
made the formation of sea ice, once predictable and reliable,
uncertain from year to year, according to Wayne Trivelpiece.
That’s directly affected the abundance of krill
and the survival rates of penguins.
In the 1970s and early 1980s, Trivelpiece explained,
the researchers would find krill of many different sizes
and age-classes (from juveniles to old adults) as they
examined the contents of the penguins’ stomachs.
But into the 1980s and ’90s, bird biologists were
fascinated by what they no longer saw — variety.
The diets were now dominated by one age-class or size
of krill each season, Trivelpiece explained. One year
juveniles would dominate, and then each succeeding year
the prey were a little bigger. The cycle would restart
every four to six years.
“As we looked at this over time, there were very
logical and predictable features to the size and age classes
of the krill in the diets,” he explained. “The
major thing that correlated with the krill size changes
was having ice in wintertime or not having ice in wintertime.”
Krill were only being replenished every few years, in
concert with winters that had heavy pack ice in the Antarctic
Peninsula region, meaning lean sources of food for many
marine predators in the intervening seasons. The Adélie
and chinstrap populations, in particular, crashed by the
late 1980s and early 1990s, according to Trivelpiece.
The Adélie population dropped by 50 percent at
King George Island by 1990. Young penguins were no longer
returning to the colony to breed as they had in previous
years. The early years of the study found 40 to 60 percent
survived to return to their breeding colonies; less than
10 percent survive today.
A krill survey in the Antarctic Peninsula region in 2000
estimated the krill population itself has dropped off
by as much as 80 percent since the last survey in the
early 1980s in the region.
“We had a vast change in the probability that young
penguins fledgling off our beaches would be seen again
in the colony two to five years later as breeders,”
Trivelpiece said. “They were basically starving to
death in much greater degree than ever before. That trend
has continued to today.”
Unique collaboration of agencies
Wayne Trivelpiece began working on King George Island
in 1976 for his PhD in zoology out of a tent camp that
first season. Poland established a research station in
Trivelpiece’s study area along Admiralty Bay in 1977,
and until 1985, he and later Susan worked at the Henryk
Arctowski Station as guests and visiting scientists of
the Polish.
In 1985, NSF established a new camp (named Copacabana,
or Copa) a few kilometers from Arctowski to continue the
long-term study of the three Pygoscelis penguins. In 1997,
NOAA incorporated the project into its Antarctic Marine
Living Resources (AMLR) program established by the AMLR
Convention Act of 1984, with the goal of managing the
Southern Ocean resources through an ecosystem approach.
Since that time, NSF and NOAA have been partners in supporting
the research at Copa.
On the Peninsula
The United States passed the AMLR Act in response to an
international treaty, the Convention for the Convention
of the Conservation of Antarctic Marine Living Resources
(CCAMLR) , established in 1982 over the concerns of krill
commercial fishing. The treaty between 25 nations seeks
to manage Antarctic fisheries to preserve species diversity
and stabilize the entire Antarctic marine ecosystem.
About 10 years ago, NOAA invited Wayne Trivelpiece to
supervise the seabird research at Copa and at the newly
constructed NOAA camp on Livingston Island called Cape
Shirreff. NSF and NOAA collaborate on supporting the camps,
with the former opening the two facilities in October
and November with its research vessel the ARSV Laurence
M. Gould . NOAA’s RV Yuzhmorgeologiya, a Russian
vessel, and staff then shutter the camps for the winter
in March.
“The two agencies recognized the scientific and
applied values of the long-term study and that it was
unique in that respect. It appealed to both of them,”
Wayne Trivelpiece says of the agreement. “We couldn’t
do our program at all without NSF’s help. We couldn’t
get anyone in to our field camps early in the year because
we don’t have our own ship until January. I think
this is a really great marriage for both of the agencies.”
More signs of climate change
For many years, however, the Trivelpieces were NSF grantees.
Much has changed in the last four decades, and there are
more visible signs of climate change in the Antarctic
Peninsula region than what scientists are finding in the
bellies of penguins.
The researchers spend many of their days hiking to penguin
colonies and skua nests. Two big chinstrap colonies about
15 kilometers away used to require crossing a pair of
glaciers. Two large lakes now sit in front of the glaciers.
“Those glaciers have receded so much that one has
become quite dangerous to cross,” noted Susan Trivelpiece,
who arrives on the island each year in October. “NSF
has given us canoes to transit in front. That’s worked
out well.”
Wayne Trivelpiece said the melting glaciers should be
physical proof to many climate skeptics that the world
is warming on a grand scale. “We are now canoeing
across these mile-wide lakes where 80-foot glacier cliffs
used to stand,” he said.
A better strategy for survival
It’s not all bad news on King George Island. While
the Adélies and chinstrap penguins struggle for
survival, the gentoos, recognized by the wide white stripe
extending like a bonnet across the top of its head, are
thriving. Other researchers in the region, including Bill
Fraser and Ron Naveen, have identified similar trends.
[See stories: Local extinction and Losing count.]
Wayne Trivelpiece said the gentoos, larger than the Adélies
and chinstraps, enjoy a more varied diet, relying less
on krill than its smaller cousins do.
“These animals have done well,” he said. “They’ve
hung in there, and seemingly increasing in numbers now,
taking up some of the slack, if you will, of the Adélies
and chinstraps.”
Diet alone doesn’t explain the gentoos’ success.
They’re also the only species that doesn’t migrate
in the winter to distant oceanic or pack ice habitats.
Instead, as homebodies, they remain in the same hunting
grounds but in much smaller colonies, usually with only
a few hundred birds. Adélies and chinstraps can
congregate in the hundreds of thousands.
The birds also mature differently, with Adélie
and chinstrap chicks expected to forage on their own at
about seven weeks of age. In contrast, gentoo adults support
their young for up to 12 weeks, including the final couple
of weeks when chicks go to sea where they can feed with
adults.
“This may allow young gentoos to learn a little
bit about what’s going on out there, and still be
sustained by being fed at night at their colonies,”
Trivelpiece said.
Keeping krill in stock
The data on the penguins are important for managing commercial
krill fisheries, one of the primary goals of CCAMLR and
AMLR. At this point, Wayne Trivelpiece said, climate change
is the primary cause in the decline of krill due to the
reduction of sea ice.
A May 2008 article by news agency Reuters said the annual
commercial krill catch is only about 100,000 tons, well
within what CCAMLR considers sustainable. That’s
down significantly from the 1980s peak of 500,000 to 600,000
tons when the former Soviet Union fished the waters, according
to Trivelpiece.
But there are signs the fishery could see more intense
activity in the next few years. Krilloil is rich in omega-3
fatty acids, a popular dietary supplement found in not
only pills but also milk and other foods. Fisheries also
harvest the small crustaceans for special enzymes that
can be used by surgeons to clean wounds, according to
Reuters, while the pinkish remains after processing can
be used as meal for salmon fish farms.
“The potential of the krill story is that the competition
for protein of whatever form is becoming more and more
acute,” Denzil Miller, Executive Secretary of CCAMLR,
based in Hobart in southern Australia, told Reuters.
“I think in the next two to three years we are going
to see a lot of changes in the way governments and the
international community addresses problems of expectation
around food security,” he added.
In addition, a Norwegian company has created a new way
to harvest and process krill continuously, Reuters reported.
Previously, it was hard to catch and then later process
large amounts of krill because the enzymes inside them
break down quickly, spoiling much of the catch.
CCAMLR currently has a 4 million-ton catch limit for
Scotia Sea. Trivelpiece said one of the key pieces of
conservation CCAMLR is working on is to divide that up
into smaller management areas based on the four main island
groups in the region. That will help ensure that the entire
quota is not taken within the area adjacent to the islands
where the penguins and seals would compete with humans
for the krill.
“The fishery can’t concentrate their fishing
in all in one area, where everybody believes if they were
to do that it would adversely affect the predators,”
he explained. “We’re trying to get all of this
in place now, while the krill fishery is what all of us
consider pretty modest.”
-
Antarctic
Sun
|
