Tuesday, November 17, 2009

Penguins and Sea Lions Help Produce New Atlas

Southern elephant seals were fitted with GPS collars to help provide data for the new atlas. (Credit: Valeria Falabella/Wildlife Conservation Society)

Penguins and Sea Lions Help Produce New Atlas

ScienceDaily (Nov. 16, 2009) — Recording hundreds of thousands of individual uplinks from satellite transmitters fitted on penguins, albatrosses, sea lions, and other marine animals, the Wildlife Conservation Society (WCS) and BirdLife International have released the first-ever atlas of the Patagonian Sea -- a globally important but poorly understood South American marine ecosystem.

The atlas contains the most accurate maps ever assembled for this ecosystem revealing key migratory corridors that span from coastlines to deep-sea feeding areas off the continental shelf hundreds of miles away.

Data for the atlas was gathered by a team of 25 scientists working over a 10-year period -- many of them supported by the National Research Council of Argentina (CONICET). The team tracked 16 species of marine animals, which produced some 280,000 individual uplinks of data over the Patagonian Sea, a huge area ranging from southern Brazil to southern Chile.

Called Atlas of the Patagonian Sea: Species and Spaces, the 300-page book was edited by Valeria Falabella and Claudio Campagna of the Wildlife Conservation Society, and John Croxall of Birdlife International.

The atlas, which is in English and Spanish, will be used to help inform potential policy decisions in the region such as managing fisheries and charting transportation routes of oil tankers. This vast region, which spans 3 million square kilometers (1.1 million square miles), is becoming increasingly threatened by burgeoning development and overfishing.

"This unprecedented atlas was essentially written by the wildlife that live in the Patagonian Sea," said Dr. Claudio Campagna who runs the Wildlife Conservation Society's "Sea and Sky" initiative. "The atlas helps fill in many gaps of knowledge and should serve as a blueprint for future conservation efforts in this region."

"This is an exceptional collaborative achievement; now that we know where some of the region's most important marine areas are, they need to receive appropriate protection and management," said John Croxall, Chair of BirdLife's Global Seabird Programme.

The atlas underscores the need to establish a new network of marine protected areas that would include open-sea environments that are linked to key coastal areas. Many of the species tracked travel vast distances between coastal breeding grounds and feeding areas. For example, satellite data revealed that southern elephant seals travel more than 10,000 kilometers (6,200 miles) during an average season at sea, and an additional 10,000 kilometers in repeated vertical dives for food.

"The Patagonian Sea is a remarkable intersection of global physics, marine biodiversity, and climate and economic change," said Dr. Steven E. Sanderson, President and CEO of the Wildlife Conservation Society. "The Atlas of the Patagonian Sea will advance conservation of this region and can serve as a roadmap for the creation and management of future marine protected areas -- of which there are precious few worldwide."

The list of species tracked for the atlas includes five species of albatross, three species of petrel, four varieties of penguin, two fur seal species, the South American sea lion, and the southern elephant seal.

The completion of the Atlas of the Patagonian Sea is due in large part to the generosity and long-standing support of the Liz Claiborne and Art Ortenberg Foundation for the WCS "Sea and Sky" initiative. Additionally, WCS's conservation work in this region has been supported by the Mitsubishi Foundation for the Americas and Mr. and Mrs. James M. Large, Jr.
Adapted from materials provided by Wildlife Conservation Society, via EurekAlert!, a service of AAAS.

Wildlife Conservation Society. "Penguins and sea lions help produce new atlas." ScienceDaily 16 November 2009. 17 November 2009 .

Thursday, November 12, 2009

News: Penguin DNA

Adelie penguins have survived in Antarctica for thousands of years and are invaluable for genetic research. (Credit: Image courtesy of Oregon State University)

Ancient Penguin DNA Raises Doubts About Accuracy Of Genetic Dating Techniques

ScienceDaily (Nov. 10, 2009) — Penguins that died 44,000 years ago in Antarctica have provided extraordinary frozen DNA samples that challenge the accuracy of traditional genetic aging measurements, and suggest those approaches have been routinely underestimating the age of many specimens by 200 to 600 percent.

In other words, a biological specimen determined by traditional DNA testing to be 100,000 years old may actually be 200,000 to 600,000 years old, researchers suggest in a new report in Trends in Genetics, a professional journal.

The findings raise doubts about the accuracy of many evolutionary rates based on conventional types of genetic analysis.

"Some earlier work based on small amounts of DNA indicated this same problem, but now we have more conclusive evidence based on the study of almost an entire mitochondrial genome," said Dee Denver, an evolutionary biologist with the Center for Genome Research and Biocomputing at Oregon State University.

"The observations in this report appear to be fundamental and should extend to most animal species," he added. "We believe that traditional DNA dating techniques are fundamentally flawed, and that the rates of evolution are in fact much faster than conventional technologies have led us to believe."

The findings, researchers say, are primarily a challenge to the techniques used to determine the age of a sample by genetic analysis alone, rather than by other observations about fossils. In particular, they may force a widespread re-examination of determinations about when one species split off from another, if that determination was based largely on genetic evidence.

For years, researchers have been using their understanding of the rates of genetic mutations in cells to help date ancient biological samples, and in what's called "phylogenetic comparison," used that information along with fossil evidence to determine the dates of fossils and the history of evolution. The rates of molecular evolution "underpin much of modern evolutionary biology," the researchers noted in their report.

"For the genetic analysis to be accurate, however, you must have the right molecular clock rate," Denver said. "We now think that many genetic changes were happening that conventional DNA analysis did not capture. They were fairly easy to use and apply but also too indirect, and inaccurate as a result."

This conclusion, researchers said, was forced by the study of many penguin bones that were well preserved by sub-freezing temperatures in Antarctica. These penguins live in massive rookeries, have inhabited the same areas for thousands of years, and it was comparatively simple to identify bones of different ages just by digging deeper in areas where they died and their bones piled up.

For their study, the scientists used a range of mitochondrial DNA found in bones ranging from 250 years to about 44,000 years old.

"In a temperate zone when an animal dies and falls to the ground, their DNA might degrade within a year," Denver said. "In Antarctica the same remains are well-preserved for tens of thousands of years. It's a remarkable scientific resource."

A precise study of this ancient DNA was compared to the known ages of the bones, and produced results that were far different than conventional analysis would have suggested. Researchers also determined that different types of DNA sequences changed at different rates.

Aside from raising doubts about the accuracy of many specimens dated with conventional approaches, the study may give researchers tools to improve their future dating estimates, Denver said.

Collaborators on the research included scientists from OSU, Griffith University in Australia, the University of Auckland in New Zealand, Massey University in New Zealand, University of North Carolina in Wilmington, the Scripps Research Institute, and Universita' di Pisa in Italy.

The studies were supported by the National Science Foundation, National Geographic Society, and other agencies.
Adapted from materials provided by Oregon State University.

Oregon State University. "Ancient Penguin DNA Raises Doubts About Accuracy Of Genetic Dating Techniques." ScienceDaily 10 November 2009. 12 November 2009 <http://www.sciencedaily.com­ /releases/2009/11/091110135411.htm>.

Monday, November 2, 2009

Changing Diet

Cape Adare is home to the largest Adélie penguin colony in Antarctica. Until about 200 years ago, when humans decimated whale and seal populations, the penguins subsisted mainly on fish. But the ensuing surplus of krill created by the dearth of top predators caused a shift in diet. Photo Credit: Steve Emslie

Photo Credit: Michael Polito
Adélie penguins march along Brown Bluff at the northern end of the Antarctic Peninsula.

Changing diet
Krill surplus 200 years ago may have caused penguins to shift prey preferences
By Peter Rejcek, Antarctic Sun Editor
Posted October 30, 2009

Most of us have heard the oft-repeated phrase, “You are what you eat.” Turns out it’s not just a way for your mother to nag you about your poor eating habits.

By studying the tissue remains of penguins in Antarctica, scientists are not only learning more about the modern diet of the continent’s iconic seabird but also what was on the menu thousands of years ago. And that information can provide insight into past climate and penguin behavior, as well as how the species could respond to future climate changes.

Steve Emslie External Non-U.S. government site, a marine ornithologist in the Department of Biology and Marine Biology External Non-U.S. government site at the University of North Carolina Wilmington External Non-U.S. government site, and his team are in the midst of a five-year grant from the National Science Foundation (NSF) External U.S. government site to determine how changes in climate and penguin prey dynamics have influenced the seabird population.

Much of their work involves collecting tissue samples, such as eggshells and feathers, from existing penguin colonies and long-extinct ones around the Antarctic Peninsula and the Ross Sea regions. Then they analyze the samples in the lab, looking at the ratios of carbon and nitrogen stable isotopes, which can provide important clues to what’s been on the dinner plate throughout the year.

“It’s mainly based on the fact that you are what you eat,” explained Emslie, who will return to McMurdo Station External U.S. government site and Ross Island this summer season to continue his fieldwork as the principal investigator (PI) on the project. “Whenever you eat something, you’re absorbing the carbon and nitrogen isotopes that are stored in that food. That ratio of carbon and nitrogen isotopes will be a part of your tissues as long as you’re eating that food.”

For example, shifts in carbon isotope ratios can indicate if a bird feeds inshore or in the marine environment. Nitrogen isotope ratios indicate how far up or down an animal feasts on the food chain.

“We look at that as a way to assess diet and how it has shifted through time as well with the Pygoscelis penguins, and also through space by the different colonies in the different regions of the Antarctic,” Emslie said.

In a study published two years ago in the journal Proceedings of the National Academy of Sciences, Emslie and collaborator William Patterson suggested that the krill-centric diet of today’s Adélie penguin is a recent phenomenon, a shift that occurred maybe 200 years ago. Their suggestion is based on a change in the nitrogen stable isotope ratio in penguin tissue.

Two hundred years ago is about the time when whalers began decimating the waters around Antarctica of krill-eating whales and seals, creating what Antarctic scientists in the 1960s and 1970s labeled as a “krill surplus,” Emslie said.

“It makes sense,” he said. “Krill per gram are just as rich in protein as fish but during a krill swarm, you can gather a lot more food a lot more quickly than you could in a school of fish. We think that’s probably why they did that switch — when krill became more abundant — even though fish were probably still available.”

Now the scientists are testing the idea further by looking at gentoos, another Pygoscelis penguin, a mostly subantarctic bird that is pushing its way across the northern end of the Antarctic Peninsula as the climate there warms and the Adélie population declines.

“We’re not sure it will show up because gentoos are known to eat a lot more fish and squid in their diet anyway compared to Adélies,” Emslie said.

The scientists know the shift in diet for the Adélies in the Ross Sea region is relatively recent because tissue samples dating back at least 40,000 years from extinct colonies in the region suggest a diet richer in fish. “Surprisingly, there weren’t any noticeable shifts [in diet] between warm and cold [periods] that are known from ice core records,” Emslie said.

“That was kind of a surprise as to why there would be a sudden shift in diet historically that wasn’t related with these climate intervals,” he said, referring to the krill surplus that resulted from whaling.

Emslie said it’s difficult to pin down an exact date on when Adélies began to prefer krill, but it was certainly happening by the beginning of the 20th century based on an analysis of Adélie eggs stored in explorer Robert F. Scott’s Hut on Cape Evans that were collected from a nearby colony sometime between 1911-1917.

“They became a nice historical sample to run isotope analysis on to see if the dietary switch had occurred by the early 1900s, and the data suggest that it had,” Emslie said. “On the peninsula you would expect it to occur first because it was hit hard first by the sealers and whalers.”

Research suggests modern Adélie diet not as krill-centric as scientists once thought

Michael Polito External Non-U.S. government site, a graduate student in Emslie’s lab External Non-U.S. government site and co-principal investigator on the project, has been working around the Antarctic Peninsula collecting penguin tissue samples from extant, or existing, colonies. By comparing the data from the stable isotope analysis to what other penguin researchers have found by physically looking at the stomach contents of the penguins, Polito hopes to refine the isotope methodology.

“They’re both useful, especially when you can use them together you can get more information than you could get just by one method alone,” he said.

For instance, it’s possible to determine the exact species of fish from stomach contents, but underestimate the mass of fish consumed, as fish digest rapidly in a penguin’s stomach, Polito said. In contrast, the stable isotope method can’t readily determine what fish species the penguins are eating, but it can provide a good estimate on how much fish the penguins consume versus krill and other prey in the ocean.

In addition, stomach content data are limited to when the penguins are on land rearing their chicks. The isotope method can also provide information about penguin diets outside of the breeding season.

And based on early results, it appears the Adélies aren’t always as reliant on krill as one might suppose from looking at what’s in their bellies during the austral summer.

“We’re definitely finding that the isotopes in general do predict a higher composition of fish in the diet than the stomach content do. It still looks like during the chick-rearing period krill are still dominant,” Polito said. “Based on the isotope data, fish appear to be relatively more important to penguins during the pre-breeding period than the breeding period.”

That finding is important but puzzling. Researchers working along the Antarctic Peninsula have reported that Adélie colonies are disappearing, their fate apparently linked to the diminishing sea ice in the region from warming temperatures. Krill also use sea ice as a key habitat. Hence, the Adélies face a double climate whammy — loss of their sea ice habitat and loss of a primary prey.

But if fish still remain a staple, why are Adélie numbers declining so dramatically? Scientists don’t really have an answer at this point. Emslie noted that part of the problem is that fish have become highly depleted as well from fisheries. “That means they have no other choices left,” he said of the Adélies.

Polito’s work to improve the isotope methodology also involves determining what other variables may be at work influencing the carbon and nitrogen ratios. For example, it turns out the size of the krill — from the juvenile stage to the adulthood — might affect their stable isotope ratio.

“Once we know how variable krill is and why it’s variable, that’s going to allow us to predict with greater accuracy the penguin diet itself.

“The modern work that we do is really designed to gain more insight about the past as well as the future,” Polito added. “We want to know how penguins respond to changes in their environment, be it climate or food availability.”

NSF-funded research in this story: Steven Emslie, Michael Polito and William Patterson, University of North Carolina Wilmington, Award No. 0739575


Penguins on the Edge

Scientists use screens to sift through dirt on Beaufort Island, searching for remains of ancient penguin colonies. Ornithologist Steve Emslie has found remains as old as 40,000 years on Beautfort Island.

A scientist examines molt layers in a glacial moraine on Beaufort Island.

Penguins on the edge
Location of ancient colonies follow the ebb and flow of Antarctic ice
By Peter Rejcek, Antarctic Sun Editor
Posted October 30, 2009

Location, location, location. For marine ornithologist Steve Emslie External Non-U.S. government site, the long-abandoned homes of Adélie penguins in Antarctica are markers in time that help define how far the continent’s ice sheets advanced and retreated for the last 45,000 years.

“The whole pattern of the colonies coming in and out of the Ross Sea fits really nicely with the forward and backward movement of the ice sheet,” said Emslie, the principal investigator on a National Science Foundation External U.S. government site grant to study how population dynamics of the three Pygoscelis penguin species in Antarctica relate to changes in prey availability and climate.

Scientists have a pretty good idea of what the climate in Antarctica was like over the last 45 millennia thanks largely to the atmospheric record from ice cores. Less well known is the location of the ice sheet edge as the atmosphere alternately warmed and cooled.

By locating and dating Adélie penguin colonies, mainly in the Ross Sea region, Emslie has been able to interpret how the ice moved. That’s because penguins re-establish their seasonal colonies in the same ice-free areas every year unless conditions force them to move.

For instance, in a study published in Geology in 2007, Emslie and his colleagues, geologists Larry Coats and Kathy Licht, determined from the existence of former colonies along the Victoria Land coast that open water existed in the southern Ross Sea from about 40,000 to 27,000 years ago. Then the ice began to advance, reaching as far as Coulman Island, about 300 kilometers north of the current edge of the Ross Ice Shelf External U.S. government site.

The climate pendulum began to swing the other away about 13,000 years ago with the start of the warmer Holocene. As the ice retreated back south, the penguins returned and re-colonized the coast, especially the Scott Coast in the southern Ross Sea, Emslie said.

Then, about 2,000 years ago, a cold snap or perhaps the presence of too much sea ice, caused the penguins to leave their colonies for a thousand years, most apparently retreating to Cape Adare far to the north, where radiocarbon dates indicate that occupation began there at that time.

“Cape Adare is now the largest Adélie penguin colony in the Antarctic, but it is definitely not the oldest,” Emslie noted.

Even after ice conditions became more favorable for the Adélies to return south, they didn’t, except for some apparently intrepid birds that founded the large colonies around Ross Island today, according to Emslie.

“So far, the data indicate that Adélie penguins, even though they’re super abundant on Ross Island today, that only occurred in the last 500 years,” he said. “They still have not reoccupied the Scott Coast, probably because of persistent annual sea ice that blocks access to that shoreline.”

Emslie and members of his research team, including a geologist from China, will revisit previous sites at Cape Bird and Cape Crozier to collect more tissue samples such as feathers, eggshells and even mummified bodies. The scientists use the organic material for radiocarbon dating — measuring the radioactive decay of radioisotope carbon-14 — to determine the age of the remains.
Molt layers in a glacial moraine.
Photo Credit: Steve Emslie
A scientist examines molt layers in a glacial moraine on Beaufort Island.

The field plan also calls for searching for more remains on Beaufort Island, which hosts the oldest samples, dating back more than 40,000 years.

Emslie’s group is one of very few using the historical location of animals like penguins to interpret ice conditions in the past. Another team, led by Brenda Hall External Non-U.S. government site with the University of Maine External Non-U.S. government site, has done similar work in the region using abandoned elephant seal colonies. [See previous article: Cradle to grave.]

Any differences? Well, it sounds like it’s much easier to locate lost penguin colonies than elephant seal colonies, where there are no definite signs to mark the remains, requiring the researchers to get down on hands and knees to search for bits of tissue from skin and hair.

Not so with Adélie penguin colonies, where the birds stack pebbles into little mounds to make a nest.

“Once you have an eye for what an abandoned colony looks like, they stand out pretty well. You can often see them from a distance away,” Emslie said. “I scan large areas with binoculars and tell whether or not abandoned sites are possible.”

Then it’s a matter of digging into the ground in tightly controlled increments, screening for samples. “You excavate them like an archaeological site,” he explained.

“There’s no other place in the world where you can have such good preservation of the same species through time that is also a good indicator of environmental change like the Adélie penguin. There’s nothing in the Arctic that we can use like that,” Emslie said.

“I think it’s pretty remarkable, pretty unique to be able to do this in the Antarctic with these preserved, ancient colonies, some as old as 40,000 years looking like they were abandoned yesterday.”