Young penguins dying due to lack of food: study

Kerry Sheridan Yahoo News 11 Apr 11;

WASHINGTON (AFP) – Young penguins in the Antarctic may be dying because they are having a tougher time finding food, as melting sea ice cuts back on the tiny fish they eat, US researchers suggested on Monday.

Only about 10 percent of baby penguins tagged by researchers are coming back in two to four years to breed, down from 40-50 percent in the 1970s, said the study in the Proceedings of the National Academy of Sciences.

Chinstrap penguins, known for their characteristic head markings that resemble a cap with a black line just under the neck, are the second largest group in the area after the macaroni penguins, and are at particular risk because their population is restricted to one area, the South Shetland Islands.

"It is a dramatic change," lead researcher Wayne Trivelpiece, of the National Oceanic and Atmospheric Administration's Antarctic Ecosystem Research Division, told AFP.

"There are still two to three million chinstrap pairs in this region but there were seven to eight million two decades ago," he said.

"There is some concern now. We need to follow these animals and track them."

The 30-year study included chinstrap and Adelie penguins in the West Antarctic and tracked the abundance of their main food source, krill, which are the small shrimp-like crustacean mainly eaten by whales, seals and penguins.

Trivelpiece was a co-author on a study published in 1992 that suggested penguin populations were surging and subsiding according to changes in sea ice -- with the chinstrap doing better in warm years and the Adelie thriving in cold years.

Chinstrap penguins eat and make their nests away from the snow and ice and so are considered ice-avoiding animals, unlike their Adelie counterparts who feed in icy habitats and are seen as more vulnerable when there is less ice.

However, Trivelpiece and his co-authors now believe that krill are the real culprit for the disappearing penguin populations, and the damage affects both types of penguins.

Krill needs ice to survive, and as climate change causes more polar sea ice to melt, the tiny sea creatures cannot breed or feast on phytoplankton in the ice and their numbers fall, taking away an important source of nourishment for penguins.

"Under a scenario of global warming and increasing temperature we had prophesized that Adelies and ice-loving animals like Adelies should decline while chinstraps and ice-avoiding animals should increase," Trivelpiece said.

But shortly after the team's paper was published in the early 90s, the data began to change.

"From that point shortly thereafter onward, we lost those large fluxes and both species started behaving the same way and both started declining dramatically," he said.

"By the time we had enough data to realize what was going on with the youngsters, we realized that the big difference was between the early years when there was a lot of krill around, and the later years when there wasn't."

Over the past three decades, krill biomass has declined 38 to 81 percent, said the study.

"If warming continues, winter sea-ice may disappear from much of this region and exacerbate krill and penguin declines," it said.

The main driver of the decline in krill is climate change, but resurgent numbers of whales -- on the rise after cuts in hunting -- could be increasing the number of predators that eat krill as well, Trivelpiece said.

A large commercial fishery that is using the krill for aquaculture feeds could also be cutting back on the natural numbers, the study noted.

While the penguins are far from the verge of extinction, the researchers have urged the International Union for the Conservation of Nature to assess their status and possibly bump them higher on Red List of vulnerable species.

Penguins suffer as Antarctic krill declines
Mark Kinver BBC News 12 Apr 11;

A number of penguin species found in western Antarctica are declining as a result of a fall in the availability of krill, a study has suggested.

Researchers, examining 30 years of data, said chinstrap and Adelie penguin numbers had been falling since 1986.

Warming waters, less sea-ice cover and more whale and seal numbers was cited as reducing the abundance of krill, the main food source for the penguins.

The findings appear in the Proceedings of the National Academy of Sciences.

Antarctic krill (Euphausia superba) is a shrimp-like creature that reach lengths of about 6cm (2in) and is considered to be one of the most abundant species on the planet, being found in densities of up to 30,000 creatures in a cubic-metre of seawater.

It is also one of the key species in the ecosystems in and around Antarctica, as it is the dominant prey of nearly all vertebrates in the region, including chinstrap and Adelie penguins.

Warming to change

In their paper, a US team of scientists from the National Oceanic and Atmospheric Administration (Noaa) and the Scripps Institution of Oceanography said a number of factors were combining to change the shape of the area's environment.

"The West Antarctic Peninsula (WAP) and adjacent Scotia Sea support abundant wildlife populations, many of which were nearly [wiped out] by humans," they wrote.

"This region is also among the fastest warming areas on the planet, with 5-6C increases in mean winter air temperatures and associated decreases in winter sea-ice cover."

They added that analysis of data gathered during 30 years of field studies, and recent penguin surveys, challenged a leading scientific idea, known as the "sea-ice hypothesis", about how the region's ecosystems was changing.

"(It) proposes that reductions in winter sea-ice have led directly to declines in 'ice-loving' species by decreasing their winter habitat, while populations of 'ice-avoiding' species have increased," they explained.

However, they said that their findings showed that since the mid 1980s there had been a decline in both ice-loving Adelies (Pygoscelis adeliae) and ice-avoiding chinstraps (Pygoscelis antarctica), with both populations falling by up to 50%.

As a result, the researchers favoured a "more robust" hypothesis that penguin population numbers were linked to changes in the abundance of their main food source, krill.

"Linking trends in penguin abundance with trends in krill biomass explains why populations of Adelie and chinstrap penguins increased after competitors (fur seals, baleen whales and some fish) were nearly extirpated in the 19th to mid-20th Centuries, and currently are decreasing in response to climate change," they wrote.

The team said that it was estimated that there was in the region of 150 million tonnes of krill for predators after the global hunting era depleted the world's whale population.

During this period, data shows that there was a five-fold increase in chinstrap and Adelie numbers at breeding sites from the 1930s to the 1970s, they reported.

"The large populations of Adelie and chinstrap penguins were not sustained for long, however, and are now declining precipitously."

They added that this was happening as rising temperatures and decreases in sea-ice was altering the physical conditions required to sustain large krill populations.

"We hypothesise that the amount of krill available to penguins has declined because of the increased competition from recovering whale and fur seal populations, and from bottom-up, climate-driven changes that have altered this ecosystem significantly during the past two to three decades."

The US researchers concluded that the penguin numbers and krill abundance were likely to fall further if the warming trend in the region continued.

They wrote: "These conditions are particularly critical for chinstrap penguins because this species breeds almost exclusively in the WAP and Scotia Sea, where they have sustained declines in excess of 50% throughout their breeding range."

Fewer Penguins Survive Warming Antarctic Climate
Deborah Zabarenko PlanetArk 12 Apr 11;

Two of the most well-known penguin species in Antarctica -- chinstraps and Adelies -- are under pressure because a warmer climate has cut deeply into their main food source, shrimp-like creatures called krill.

Fewer of the juvenile penguins survive what scientists call their "transition to independence" because there isn't enough krill to go around, according to a study published on Monday in the Proceedings of the National Academic of Sciences.

The study found only 10 percent of young penguins survive the first independent trip back to their colonies from their winter habitat, said lead author Wayne Trivelpiece, a sea bird expert at the National Oceanic and Atmospheric Administration's Antarctic Ecosystem Research Division.

When the study began, back in the mid-1970s, the chances that a two-to-four-year-old penguin would survive the trip was about 50 percent, Trivelpiece said in a telephone interview.

"What's changed is young penguins surviving their transition to independence," he said. "They're no longer able to do that anywhere near the way they used to do, and we think that's directly related to the fact that there's 80 percent less krill out there now."

Initially, scientists figured one of these two penguin species might actually benefit from climate change, since Adelies love ice and chinstraps avoid it. They theorized that the chinstrap penguins might flourish with less ice and more of the open water they favor.

But this latest research suggests it is less a question of vanishing penguin habitat -- though this is also occurring -- than it is a matter of vanishing habitat for krill.

Krill form the basis of the marine food web, supporting organisms ranging from fish and penguins to whales. Krill feed on phytoplankton -- basically, ice algae -- that grow lushly on the undersides of ice floes.

These tiny crustaceans are specially adapted to graze for the tiny plants among the ice crystals. But in the last few decades, winter ice has formed later in the season and has covered less area and spring melt comes earlier. Without ice, krill's feeding is disrupted and populations fall.

Trivelpiece's research focused on an area that is experiencing some of the most extreme climate warming on the planet: the Antarctic Peninsula and the islands around it.

Mean winter temperatures have risen 9 to nearly 11 degrees F (5-6 degrees C) in that area since the mid-20th century, compared to the rise in world mean temperatures of less than 2 degrees F (about 0.74 C) for all of the 20th century.

The study was funded in part by the Lenfest Ocean Program, which supports research on the global marine environment.