More on the Adelie Penguin/Climate Change Dilemma

July 29, 2010 

Thaw deal: Climate change could leave penguins in the dark

By John Platt

 

Few animals can live totally in the dark, and penguins are no exception. But new research shows that climate change could soon rob Adélie penguins (Pygoscelis adeliae) of the sunlight they need to survive, and that could drive them into extinction.
The problem comes from melting sea ice, according to the report in the July 2010 issue of Ecology. As the climate changes and more of Antarctica's Ross Ice Shelf melts, Adélie penguins will be forced farther inland. This will take the birds away from the small amount of sunlight they have during certain parts of the year at current latitudes, leaving them unable to see, hunt or endure.

The study followed two Adélie penguin colonies on Antarctica's Ross Island for three years, using geolocation sensor tags to track them as they migrated. As winter approached, the researchers found that the penguins always stayed in areas where there was a high concentration of sea ice and where there was at least two hours of twilight a day. (As one travels farther south, there are long daylight hours in summer, but as the season advances toward winter, daylight hours grow steadily shorter until in many parts of Antarctica the sun doesn't rise above the horizon at all.) The researchers then used the migration patterns they had observed to conjecture on how those patterns have changed as the Ross Ice Shelf has retreated across the Ross Sea, off the coast of Antarctica, over the past 12,000 years (as illustrated in this animation), and in more recent decades as well as how it could change in the future.

"As sea ice extent in the Ross Sea sector decreases in the near future, as predicted by climate models, we can expect further changes in the migration patterns of the Ross Sea penguins," according to the paper's abstract.

"Ultimately, penguins around Antarctica will face darkness or lack of ice," lead author Grant Ballard of PRBO Conservation Science said in a prepared statement.

"From studying the long-term history of this species in Antarctica, we know that animals are actually very good at adapting to fluctuating conditions in their environment," Ballard said." They do this by changing their migration routes or altering other feeding behaviors. In this case, however, ice conditions are changing so rapidly the penguins may not be able to adapt in time."

The research was funded by the National Science Foundation and the U.S. Antarctic Program.
Photo: Adélie penguins, via Wikipedia

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Ancient penguin DNA raises doubts about accuracy of genetic dating techniques

 An older, but still very valid article:

Ancient penguin DNA raises doubts about accuracy of genetic dating techniques

by on November 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.

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The Fate of the Adelie Penguin

Fear of the dark may lead to penguin extinction

by bjs on July 21, 2010

Will Adélie Penguins, attempting to cope with climate change, go extinct because they can’t find food in the darkness of the Antarctic winter?  A recent paper published in the scientific journal Ecology presents this finding: Adélie Penguins need both ice and light, even just twilight, to find food in the winter.

As climate change causes the winter ice to retract south into the darkness, penguins won’t have what they need to survive and could ultimately face extinction as a result.  Like songbirds needing trees, these penguins rarely stray very far from sea ice.

Researchers from PRBO Conservation Science, H.T. Harvey and Associates, Stanford University, NASA, and the British Antarctic Survey tracked the penguins’ year round movements for the first time using geolocator tags.  Over a three year period they documented the penguins’ need for both ice and light during the winter, as reported in the Ecology paper.

“Penguins living near the Antarctic Peninsula are being forced to migrate southward to find ice in the winter. This is in direct contrast with penguins on the other side of Antarctica at the Ross Sea, and those elsewhere in Antarctica, which still need to migrate northward to find light and favorable ice in the winter. Ultimately penguins around Antarctica will face darkness or lack of ice – they’ll just reach that boundary from different directions,” says Grant Ballard, PhD, of PRBO Conservation Science and lead author of the tracking study.
This is the first study to show the complete migratory and wintering locations of Adélie Penguins. The researchers found that penguins made use of ocean currents to facilitate annual migrations averaging almost 13,000 km (~8,100 miles), and that they travel more than twice as fast on the return trips from their wintering locations to begin breeding than when they depart after breeding.  They also concluded that this migration pattern evolved in relatively recent times, since the last ice age.

“From studying the long-term history of this species in Antarctica, we know that animals are actually very good at adapting to fluctuating conditions in their environment.  They do this by changing their migration routes or altering other feeding behaviors. In this case, however, ice conditions are changing so rapidly the penguins may not be able to adapt in time,” says Dr. Ballard.

This study builds on another recent publication in Ecological Monographs by many of the same scientists that indicates major changes in sea ice extent will be underway within our lifetimes given the present climate trajectories.

The Ross Sea is projected to be the last place on Earth where sea ice will persist and where Adélie Penguins and other pack-ice species can exist. The findings reported by these researchers  also underscores the need to designate the Ross Sea as a Marine Protected Area, slow the progression of climate change, and look for adaptation strategies to some of these unforeseen effects of climate change.

This  research, funded and supported by the National Science Foundation and the US Antarctic Program, was conducted at two colonies in the southern Ross Sea, which is south of New Zealand.

Paper citations

Ballard, G., V. Toniolo, D.G. Ainley, C.L. Parkinson, K.R. Arrigo, P.N  Trathan. 2010. Responding to climate change: Adélie penguins confront astronomical and ocean boundaries. Ecology 91(7):2056-2069.
Link to the paper’s abstract: http://www.esajournals.org/doi/abs/10.1890/09-0688.1

Ainley, D.G., J. Russell, S. Jenouvrier, E. Woehler, P. O’b. Lyver, W.R. Fraser, G.L. Kooyman. 2010. Antarctic penguin response to habitat change as earth’s troposphere reaches 2°c above pre-industrial levels. Ecological Monographs 80: 49-66.

About PRBO Conservation Science:

PRBO Conservation Science, founded as Point Reyes Bird Observatory in 1965, works to conserve birds, other wildlife and ecosystems through innovative scientific research and outreach.  We partner with hundreds of governmental and non-governmental agencies as well as private interests to ensure that every dollar invested in conservation yields the most for biodiversity — benefiting our environment, our economy and our communities.  Visit PRBO on the web at www.prbo.org.

Note to reporters:  Our organizational name is PRBO Conservation Science, as written with the acronym (not Point Reyes Bird Observatory Conservation Science).

Petaluma, CA: Press Release for July 21, 2010
Contact:  Grant Ballard, PRBO Conservation Science, gballard@prbo.org, 707 781-2555 ext 340

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Penguins Are Regular Prey for Orcas

Antarctic orcas dine on penguins scientists discover

By Matt Walker Editor, Earth News

The hunt is on

Orcas regularly feed on penguins in Antarctica, scientists have discovered.

Although orcas are known to predate penguins further north, around sub-Antarctic islands, this is the first time they have been seen hunting the birds in Antarctic continental waters.
What is more, the orcas seem to be particularly choosy about which bits of the penguins they eat; being inclined to take only the best cuts of penguin breast meat.
Details are published in Polar Biology.

They seemed to be mainly interested in eating just the breast muscles, rather like humans would do Marine biologist Dr Robert Pitman

Marine biologists Dr Robert Pitman and Dr John Durban of the US National Marine Fisheries Service based in La Jolla, California, made the discovery while researching orca foraging behaviour around the Antarctic peninsula.
"We had expected to see killer whales taking Antarctic minke whales and seals, which we did," Dr Pitman told the BBC.
"But we were quite surprised to find them catching penguins also."
Three type of orca are known to live in Antarctic waters, each differing in size, colouration and the prey they hunt.
Type A orcas are the largest, are black and white and look most like orcas found elsewhere in the world. Type As hunt minke whales.

Unhappy feet: an orca rolls on its side with a gentoo penguin in its mouth

Type B orcas are smaller and have a yellow tinge. They also prey on minke and perhaps humpback whales but tend to prefer to hunt seals.
Type C orcas are also smaller, with different markings, and prefer to live within inshore waters and among the pack ice, and to date have been recorded only feeding on Antarctic toothfish.
Biologists have long questioned whether any of these orcas take penguins, which are also abundant on the continent, but until now there has been no evidence.
That was until Drs Pitman and Durban witnessed several instances of predation on two different species of penguins: chinstraps and gentoos.
The attacks occurred over three separate days, and were instigated by type B orcas, with some evidence that type A orcas may also have hunted and fed on a penguin.

ORCA INSIGHTS King penguins are the perfect fast food for fur seals, scientists have discovered Watch video of a massive pod of up to 50 orcas filmed for the first time off the coast of Scotland Watch videos of orcas hunting a range of prey

During each attack the orcas chased a penguin, which porpoised out of the water and erratically changed direction under water in a bid to avoid capture.
Surprisingly, when the orcas did catch a penguin, they often refrained from eating the whole bird.
"We were surprised to find killer whales eating 4 to 6kg penguins, and even more surprised to find that they seemed to be mainly interested in eating just the breast muscles, rather like humans would do," says Dr Pitman.
Often the orcas handled their prey with meticulous care, removing skin and feathers to expose the breast muscle, sonetimes working cooperatively to do so.
The breast tissue may be particularly nutritious, but it is still unclear how much nutritional benefit a 3000kg orca would get eating selective cuts of a penguin weighing just a few kilograms.

Juvenile orcas catch and kill a gentoo penguin

"Penguins have enormous breast muscles to power winged flight through the water, but it is still a small part of an already small prey item. It would be like us chasing around after individual peanuts," says Dr Pitman.
"Ours is the first clear documentation of penguin predation in Antarctic waters but we don't know how commonly it occurs."
If it is common, then predation by orcas could have a significant impact on penguin populations in Antarctica.
In the past, biologists have suspected that orcas may have been responsible for a 50% decline in numbers of emperor penguins residing at Adelie Land, eastern Antarctica during the 1970s.
But no penguin remains were found inside the stomachs of orcas in the area.

SOURCES Visit the journal Polar Biology to read more about the penguin-hunting orcas

The observations of Dr Pitman and Durban, however, suggest that these whales may have also been fussy eaters, removing breast tissue and not bones, which would leave little trace in an orca's stomach.

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New Macaroni Study

A Carryover Effect of Migration Underlies Individual Variation in Reproductive Readiness and Extreme Egg Size Dimorphism in Macaroni Penguins

 

Glenn T. Crossin (Simon Fraser University and the Natural Environment Research Council), Phil N. Trathan (Natural Environment Research Council), Richard A. Phillips (Natural Environment Research Council), Alistair Dawson (Natural Environment Research Council), Fabrice Le Bouard (Natural Environment Research Council), and Tony D. Williams (Simon Fraser University)

(176:September)

 

Two eggs over easy? Not really. Macaroni penguins, migration, and the cost of egg size dimorphism

  One of the longest standing mysteries in avian biology has been that of the extreme egg size dimorphism observed in crested penguins. Macaroni penguins spend 6 long winter months at sea, navigating Antarctic Polar Front waters, and in spring they return with great synchrony to breeding colonies to begin egg-laying. But macaroni penguins are unique among birds in that females lay one small A-egg, which never hatches, and then one larger B-egg, which does. Questions about the physiological causes (the "how") and functional significance (the "why") of this intriguing reproductive pattern have been unanswered for over 60 years. Now Canadian and British researchers have provided answers to the "how" question by revealing links between migration, reproductive physiology, and egg size.

The degree of A:B egg size dimorphism varies among individual female penguins. Some females produce an A-egg that is only about half the size of the larger B-egg, while others can produce an A-egg that is almost equal in size to the B-egg. At the same time, it is also known that some females begin egg-laying almost immediately upon their arrival at the colony while others arrive and spend about two weeks there before egg-laying. The researchers hypothesized that variation in egg size dimorphism might be the result of a "physiological conflict" due a conflict between migration and reproduction: some females must have been producing eggs while they were still actively migrating back to the colony, and perhaps these females produce the smallest A-eggs and most dimorphic clutches. Physiological sampling of arriving females confirmed that concentrations of the protein vitellogenin, the primary constituent of developing eggs, were lowest in penguins that had the greatest overlap between migration and egg formation. In other words, these females appeared less "reproductively ready." Migration is thus a key determinant of egg size dimorphism in macaroni penguins, and females who avoid physiological conflict by finishing migration before initiating egg production can produce two eggs more equal in size.

After migrating throughout the southern latitudes for more than six months, macaroni penguins arrive each spring at a breeding colony in Bird Island, South Georgia. The inset shows the dimorphism of A-eggs and B-eggs, which is the result of a physiological conflict imposed by migration. (photograph by Glenn Crossin ©)

 

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Penguin courtship tests devotion

AAP

14/07/2010

PHIL REID/Dominion Post

CALL OF THE WILD: Adelie penguin mating calls 'sound like a cross between a donkey and a stalled car'.

 

New Zealand academics have shown the female penguins in some species use courtship to decide which males are likely to be devoted dads, with fatter males their more probable choice.
Auckland University researcher Dr Emma Marks said in a study in published a science journal, Behaviour, that penguin calls hold clues to a male's paternal potential.
Adelie penguins team-parent to successfully raise a family in Antarctica: males and females take turns incubating the eggs and guarding the chicks while their mate hunts.
Males claimed a territory and built a nest, and when the females arrived, the males threw their heads back, pointing their beaks to the sky, and emitting a series of hoarse trills and squawks.
"They're not musical calls - they sound like a cross between a donkey and a stalled car," Dr Marks said in a statement from the National Evolutionary Synthesis Centre in North Carolina, USA.
The courtship calls told females how fat a male was and what kind of father he'd be, said her co-author, Associate Professor Dianne Brunton of Massey University. Fatter males made better fathers because they had good energy reserves and were less likely to leave the nest and desert their chicks.
"A fat male is a good choice for a female because males do so much of the offspring care," said Prof Brunton. "They're able to incubate the eggs for longer and use up their fat stores, while skinny males aren't able to do that."
Dr Marks spent three months of her summer near Scott Base, with half a million Adelie penguins.
She weighed dozens of males and recorded their calls, then noted how successful they were at attracting mates and raising chicks.
The researchers found that steady frequency over the longest part of the call - an extended chattering in the middle of the male's display - best predicted male buffness and mating success.
"It's as if females are listening to the stability of the call," said Dr Marks.
Males with more consistent pitch were snatched up. These males were also heavier and more successful at raising chicks.
"The fat surrounding the male's voice box changes what his call sounds like," said Prof Brunton.
"We don't yet know the physiological mechanism for call production, but body fat appears to stabilise their calls," Dr Marks said.
After choosing a mate the female laid two eggs and returned to feed at sea, leaving the male on the nest until she returned to take the next shift. Father penguins could lose more than 20 percent of their body weight over breeding season, the researchers said.

 

"It's a pretty arduous task, especially for the males," said Dr Marks. "If a male doesn't have enough fat to last these fasts, he may have to abandon the eggs ... it's imperative that the female pick a male in good condition."

Source

To lure a female to his nest, a male flaps his flippers, points his beak to the sky, and emits a series of loud trills and squawks. (Credit: Photo by Emma Marks)

Penguin Males With Steady Pitch Make Better Parents

ScienceDaily (July 12, 2010) — How does a female penguin choose a mate? Courtship calls help females decide which males are likely to be devoted dads, says a study in the journal Behaviour.

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Antarctic penguins come on land for just a few short months each summer to breed and raise their chicks. Raising a family in the coldest place on earth is no small feat. Adelie penguins pull it off by tag-team parenting, the researchers explained. Males and females take turns incubating the eggs and guarding the chicks while their mate forages for food.
Males arrive first to claim a territory and build a nest. When the females arrive, the males serenade prospective mates by throwing their heads back, pointing their beaks to the sky, and emitting a series of hoarse trills and squawks.
"They're not musical calls -- they sound like a cross between a donkey and a stalled car," said author Emma Marks of the University of Auckland. Penguin calls may not be music to our ears, but to penguin females they hold clues to a male's paternal potential, Marks and colleagues report.
After choosing a mate the female lays two eggs and returns to sea, leaving the male alone to tend the egg until she returns to take the next shift. For the first two weeks penguin dads do the bulk of babysitting duty without breaking to eat. By relying on stored fat reserves, father penguins can lose more than 20% of their body weight over the course of the summer breeding season, the researchers said.
"It's a pretty arduous task, especially for the males," said Marks. "If a male doesn't have enough fat to last these fasts, he may have to abandon the eggs and go to sea before the female can make it back. So it's imperative that the female pick a male in good condition," she added.
The researchers wanted to know how courtship calls help a penguin female choose the father of her chicks. "We knew that females preferred some males over others. But we didn't know what traits females were using to choose a good mate," said co-author Dianne Brunton of Massey University in New Zealand.
"If she chooses a male with a particular kind of call, does she have a better chance of successfully raising chicks?" Marks asked.
To find out, Marks traveled to Antarctica's remote Ross Island, summer home to half a million Adelie penguins. Over the course of the next three months she weighed dozens of males and recorded their calls with a handheld microphone. She also noted how successful they were at attracting mates and raising chicks.
When the researchers examined the calls, they found that steady frequency over the longest part of the call -- an extended chattering in the middle of the male's display -- best predicts male buffness and breeding success. "It's as if females are listening to the stability of the call," said Marks.
Males with more consistent pitch were snatched up more quickly. These males were also heavier and more successful at raising chicks, the researchers found. "The fat surrounding the male's voice box changes what his call sounds like," said Brunton. "We don't yet know the physiological mechanism for call production, but body fat appears to stabilize their calls," Marks added.
By listening to male courtship calls, a female can tell how fat a male is and what kind of father he'll be, Brunton explained. Fatter males make better fathers because they have the energy reserves to endure long fasts, so are less likely to leave the nest and desert their chicks.
"A fat male is a good choice for a female because males do so much of the offspring care," said Brunton. "They're able to incubate the eggs for longer and use up their fat stores, while skinny males aren't able to do that."
The researchers also wondered if males were always honest about their potential as caring fathers, or merely bluffing to attract a mate. "What if the guy calls, and it turns out he's a skinny bird pretending to be a fat bird, making himself sound better than he really is?" said Marks.
"Females can't judge how fat a male is just by looking at him," said Brunton. "How fat he looks depends on how he's standing and how fluffed up his feathers are."
A male who lies about his paternal commitment might increase his chances of passing on his genes, said co-author Allen Rodrigo, Director of the National Evolutionary Synthesis Center in Durham, North Carolina. For that reason, females are likely to be on the lookout for the most honest indicators of paternal potential, he explained.
As penguin dads lost weight over the chick-rearing season, their calls changed too, Marks found. "So a skinny male is unlikely to be able to pretend he's a big fat male. He can't fake it," said Marks.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by National Evolutionary Synthesis Center (NESCent), via EurekAlert!, a service of AAAS.

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Journal Reference:

1. Emma J. Marks, Allen G. Rodrigo, Dianne H. Brunton. Ecstatic display calls of the Adélie penguin honestly predict male condition and breeding success. Behaviour, 2010; 147 (2): 165 DOI: 10.1163/000579509X12512863752751

National Evolutionary Synthesis Center (NESCent). "Penguin Males With Steady Pitch Make Better Parents." ScienceDaily 12 July 2010. 13 July 2010 /releases/2010/07/100712102806.htm>.

 

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Adelies, Fish, and Climate Change

National Science Foundation
Office of Polar Programs

4201 Wilson Boulevard
Suite 755, Arlington, VA 22230

 

Photo Credit: Joseph Torres

A tabular iceberg in Antarctic Sound, a body of water at the far northern end of the Antarctic Peninsula, the only place where researchers found a relatively healthy population of silverfish.

Photo Credit: Erica Hudson The crew of the research vessel Nathaniel B. Palmer prepares to deploy a net off the stern of the ship. The net is used to capture silverfish, an important species in the Antarctic food web that appears to be vanishing along parts of the peninsula. Fishy business Climate change may be to blame for disappearance of Antarctic silverfish  By Peter Rejcek, Antarctic Sun Editor Posted July 9, 2010 Adélie penguins across parts of the northwestern Antarctic Peninsula don’t appear to be getting a balanced diet these days. What’s missing? A sardine-sized fish called Pleuragramma antarcticum, more commonly referred to as the Antarctic silverfish. Once upon a time, as the story goes, Antarctic silverfish swam by the thousands in places like Arthur Harbor at the northern end of the peninsula. “That doesn’t happen anymore,” said Joseph Torres , a professor in the College of Marine Science at the University of South Florida . Torres led a diverse team of biologists, oceanographers, geneticists and others to the region earlier this year to find out exactly what’s happened to the silverfish. Photo Credit: Joel Bellucci Antarctic silverfish It’s been about 15 years since any significant numbers of silverfish were found in the Adélie diet in the area around Palmer Station on Arthur Harbor, according to Bill Fraser, whose work in the region dates back to the 1970s and is part of the Palmer Long Term Ecological Research program funded by the National Science Foundation (NSF) . The NSF also funded the silverfish expedition. The scientists traveled aboard the research vessel Nathaniel B. Palmer , steaming about 1,200 kilometers along the western side of the peninsula, starting south at Charcot Island to the northern tip at Joinville Island, stopping at several key penguin colonies along the way. “What we wanted to do was contrast the different regions in terms of how many silverfish they had and what the diet of the penguins there was like,” Torres explained. “We were curious if the penguin diets reflected what the community was like out there.” Expected results The scientists used two methods to search for the disappearing silverfish. They towed nets from the ship along the relatively shallow waters of the continental shelf near where penguin colonies forage for food. And Fraser’s seabird researchers visited key penguin colonies on various islands. They examined the stomach contents of nearly 60 birds, as well as attached satellite tags on some penguins to monitor their foraging habits. They found silverfish where they expected to find them — in the south, where sea ice and a colder climate persist. They didn’t find them where they expected not to find them — around Palmer Station farther to the north, where ambient winter temperatures are up about 6.5 degrees Celsius since the 1950s and sea ice is a fading memory. Photo Credit: Joseph Torres An Adélie penguin near Rothera Research Station. Like other parts of the polar food web — such as Adélie penguins and shrimp-like krill — the silverfish rely on sea ice for parts of their lifecycle. For example, the sea ice offers cover when the eggs hatch in November, Torres noted. Without it, he added, “the larvae are exposed to predation in the open water.” Based on the preliminary results of the net tows and diet samples, Fraser said, “I think we can pretty substantially confirm that the silverfish have, in fact, disappeared from a very specific region of the Antarctic Peninsula, which happens to be the region that has experienced the most rapid winter sea ice loss over the last three decades.” On the other hand, silverfish still account for a substantial part of the the penguin diet for birds at Charcot and Avian Island to the south. While still awaiting more definitive analysis, Fraser said he estimated that Pleuragramma made up about half of the meals for birds on Avian and upwards of 80 percent for the most southerly Adélies at Charcot. Outclassed But the story is more complicated — and possibly grimmer — than the scientists first suspected. While they found Antarctic silverfish in the south, they saw fish dominated by only one age class, a cohort they estimate to be about 9 or 10 years old. The absence of a younger age class, a new generation, is worrisome, according to Torres. “It tells me that the population isn’t getting any new recruits,” he said. “What we’re looking at is a population that is not a healthy one.” In fact, the only bright spot was around Joinville Island in the extreme north, where currents from the Weddell Sea bring in new silverfish from the still healthy populations on the eastern side of the peninsula. But thickening sea ice and blustery weather that dropped the wind chill to minus 50 degrees centigrade made for challenging working conditions there. “The ocean was freezing too fast. We were really limited in terms of what we could do and where we could go,” Fraser said.

National Science Foundation
Office of Polar Programs

4201 Wilson Boulevard
Suite 755, Arlington, VA 22230

 

Otoliths                                                                                                                                                

 

The researchers are keenly interested in figuring out where the Charcot and Avian silverfish populations come from. That job largely falls to Julian Ashford , a professor of oceanography at Old Dominion University .
Ashford employs a technique called Inductively Coupled Plasma Mass Spectrometry, or ICPMS, that can not only tell him about where the fish were spawned, but what environmental conditions existed from year-to-year during the animal’s lifetime. All he and his team need for the analysis is an otolith — a small ear bone.

Photo Credit: Penguinscience.com

Fish otoliths. The small, rounded ones are from Antarctic silverfish.

The otolith is made mainly of calcium carbonate, like corals, which is different than most bones of the body, which are made of calcium phosphate. Juvenile fish lay down new layers of bone every day, while older fish create new layers every year, corresponding to winter and summer. Ashford said scientists can count the rings of an otolith to determine the fish’s age, just like a tree ring.
Trace elements found in the calcium matrix, on the other hand, can offer clues to the kind of conditions that existed throughout the critter’s lifetime. For example, the chemical element strontium can indicate water temperature.
“What you’re getting is a kind of environmental record that’s related to chronology, and the fish are constantly putting that down throughout their life history,” Ashford said.

Photo Credit: Joseph Torres

The research vessel Nathaniel B. Palmer tied up at the pier of Rothera Research Station off the Antarctic Peninsula.

The researchers can follow the chemical tracers in the otoliths like breadcrumbs, mapping the fish’s route through different parts of the water column and different regions. So, for example, separate populations of silverfish that were spawned in different areas will have a different signature from each other.
“They’ll be recording water peculiar to their spawning area,” Ashford said. “It’s terribly important to know what proportion of fish you have in a particular area is self-recruiting from a local population and how many are migrating in from other populations.”

Common source

Ashford said he suspects the Charcot and Marguerite populations share a common source based on the demographics. The chemistry work from the otoliths will confirm those suspicions.
Previous research has shown that krill are also dominated by certain age classes, likely related to environmental cycles, particularly sea ice.
“It may be that similar events are driving the Pleuragramma,” Ashford noted.
Another team of collaborators from Italy collected tissue samples at the same time Ashford extracted his otolith specimens. The Italians will analyze the silverfish’s genetic characteristics and compare them to other silverfish from around the Southern Ocean, according to Torres.

Photo Credit: Joseph Torres

Fur seals are among the predators that prey on silverfish.

“We have two lines of evidence being worked up now to see where they came from and who they are most closely related to. That’s a pretty nifty thing,” he said.
The results from the cruise will establish an important baseline for researchers to track the future progress of the Antarctic silverfish along the Antarctic Peninsula, Torres added.
“When this fish is missing from the smorgasbord for penguins and other seabirds, [the predators] tend to decline in numbers,” he said. “The silverfish is the only Antarctic coastal pelagic fish that is accessible to all predators. It is extremely important.”
NSF-funded research in this story: Joseph Torres, University of South Florida, Award No. 0741348 ; Julian Ashford, Old Dominion University, Award No. 0741362 ; and Bill Fraser, Polar Oceans Research Group, Award No. 0741351 .

Source 

Penguins Matter

For the past several years, I have maintained 3 online blogs that constantly keeps the concern for penguins in the online community's minds, if not their hearts. I helped an agency with their efforts to sue the federal government for their neglect in protecting penguins by obtaining 500 signatures whose support and intent were unmistakeable. And I have preached to the uninitiated of the necessity to preserve our southernmost neighbors and their environment, for if those penguins become extinct, we surely will follow.

Please vote for me so that I can continue my work and relay to you all what the eye sees and the mind interprets upon that vast country known as Antarctica and its precious inhabitants.


Thank you!


Go HERE to register and vote, please... I do need your help.


Lin (aka wiinterrr)