Friday, August 23, 2013

Food Source for Penguins at Risk: Warming Antarctic Seas Likely to Impact On Krill Habitats

Aug. 22, 2013 — Antarctic krill are usually less than 6 cm in length but their size belies the major role they play in sustaining much of the life in the Southern Ocean. They are the primary food source for many species of whales, seals, penguins and fish.

Krill are known to be sensitive to sea temperature, especially in the areas where they grow as adults. This has prompted scientists to try to understand how they might respond to the effects of further climate change.

Using statistical models, a team of researchers from the British Antarctic Survey and Plymouth Marine Laboratory assessed the likely impact of projected temperature increases on the Weddell Sea, Scotia Sea and Southern Drake Passage, which is known for its abundance of krill. This region has experienced sea surface warming of as much as 1°C over fifty years. Projections suggest this could rise by another 1°C by the end of the 21st century.

The models are based on equations which link krill growth, sea surface temperature, and food availability. An analysis of the results, published this week in the online journal PLOS ONE, suggests warming, if continued, could reduce the area of growth habitat by up to 20%.

In the early life stages krill require deep water with low acidity and a narrow range of temperatures for their eggs to successfully hatch and develop. The larvae then feed on algae on the underside of sea ice.

The adults require suitable temperatures and enough of the right type of food (larger phytoplankton) to successfully grow and reproduce. Many of these critical environmental features (temperature, acidity, sea ice and food availability) could be affected by climate change.

The projected effects of warming are not evenly spread. The island of South Georgia is located within the area likely to be worst affected. Here the reduction in krill habitat could be as much as 55%. The island is home to a range of animals such as fur seals and macaroni penguins that depend upon krill, and others, such as black-browed albatrosses, which eat substantial amounts of krill as well as fish and squid. The researchers say animals which don't travel far to forage, such as fur seals, would be most affected by the projected changes.

Krill is also being commercially fished, although there is nothing to suggest current levels are unsustainable. In fact, at less than 1% of estimated biomass, catches are much lower than most other commercial fisheries.

But the Antarctic krill fishery took 68% of its total catch between 1980 and 2011 from the area of projected habitat degradation. The scientists suggest improved management systems to ensure the fisheries take into account both growing demand for catches and climate change.

Lead author, Dr. Simeon Hill, a marine biologist at BAS, said: "Each year, growth of Antarctic krill in the Southern Ocean produces new material that weighs twice as much as all the sugar produced in the world. Krill grow fastest in cold water and any warming can slow down or stop growth, reducing the food available for wildlife. Our research suggests that expected warming this century could severely reduce the area in which krill can successfully grow."

Although there is evidence that warming seas pose a threat to Antarctic krill habitats the team of researchers believe this can be mitigated with effective fisheries management systems in place.

Story Source:
The above story is based on materials provided by British Antarctic Survey.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:
  1. Simeon L. Hill, Tony Phillips, Angus Atkinson. Potential Climate Change Effects on the Habitat of Antarctic Krill in the Weddell Quadrant of the Southern Ocean. PLoS ONE, 2013; 8 (8): e72246 DOI: 10.1371/journal.pone.0072246

British Antarctic Survey (2013, August 22). Food source for whales, seals and penguins at risk: Warming Antarctic seas likely to impact on krill habitats. ScienceDaily. Retrieved August 23, 2013, from­ /releases/2013/08/130822091032.htm
Also, a more elaborate report is posted on the National Geographic website: HERE 

Thursday, August 22, 2013

Penguins Thrived in Antarctica During Little Ice Age

Here a colony of penguins on the Fildes Peninsula, which is located off the coast of Antarctica on King George Island, the largest of the South Shetland Islands.
Here a colony of penguins on the Fildes Peninsula, which is located off the coast of Antarctica on King George Island, the largest of the South Shetland Islands.
Credit: Zhouqing Xie
Penguin populations in the Ross Sea of Antarctica spiked during the short cold period called the Little Ice Age, which occurred between A.D.1500 and 1800, new research shows.

The results run contrary to previous studies that found increases in Antarctic penguin populations during warmer climates and decreases during colder climates, suggesting penguin populations living at different latitudes in the Antarctic may respond to climate change differently, scientists said.

"How ecological systems adapt to climate change is a very important and hot topic," said study researchers Liguang Sun and Zhouqing Xie, who are both environmental scientists at the University of Science and Technology of China in Hefei, China. "Our study suggests that it is not simple to answer this question," they told LiveScience in an email.

Determining penguin populations

The researchers and their colleagues have been studying the historical changes in penguin populations in the maritime Antarctic for more than a decade. Previous work had suggested the birds actually thrive when the climate is relatively warm, because cold climates increase sea-ice extent, which makes it difficult for penguins to access their beach colonies and waters that are rich in food (krill).

For the new study, the researchers decided to take a look at how the populations of Adélie penguins (Pygoscelis adeliae) changed over the past 700 years in the Ross Sea
, a region in Antarctica that is at a higher latitude than previous study sites. They analyzed sediment samples from multiple depths for cholesterol and cholestanol, which are biomarkers indicating soil contamination by animal feces (either from seals or penguins in Antarctica). They also analyzed the samples for two organic compounds related to algae and lichens, respectively.

Based on the variation in the markers, the team divided up the timeline into four periods. Seals dominated the study site during Period I, which occurred between A.D. 1280 and 1490 — the researchers determined the biomarkers came from seals rather than penguins because of the presence of seal hairs in the layers of sediment. After A.D. 1490, seal hairs disappeared from the samples, suggesting the animals left the area and never returned, though the researchers aren't sure why.

According to the biomarkers, penguin populations boomed during Period II (1490 to 1670), declined significantly during Period III (1670 to1950) and increased steadily since then in Period IV (1950 to present).

The amounts of vegetation corroborated the penguin data. Antarctic algae require a lot of nutrients from penguin droppings to thrive, whereas penguin trampling endangers lichens: The evidence shows that algae abundances increased and decreased along with the penguin populations, but lichen abundances showed the opposite trend.

On the rise

The researchers note a number of factors affect penguin populations, including temperatures, sea-ice extent, food, wind and snow cover. The summer temperatures during the Little Ice Age were about 2 degrees C (3.6 degrees F) colder than the previous 200 years — this chilly climate promoted more sea-ice extent, which would normally be detrimental to penguins.

However, ice core samples suggest that strong winds broke up the sea ice during Period II, allowing the birds to access their beach colonies. These winds also likely affected snow precipitation, resulting in low snow accumulation that allowed the penguins to build their nests.

Additionally, the penguins could dive into the pockets in the sea ice to eat krill, which were likely abundant because of all the algae growing under the sea ice (krill feed on algae).

Adélie penguin populationsare on the rise again now, because the climate is getting warmer and the Antarctic is experiencing a reduction in sea-ice extent, the researchers said.

The team is currently trying to track the long-term changes in krill populations by measuring nitrogen isotopes, or atoms of nitrogen with a different number of neutrons, in the feathers and bones of penguin remains. They are also interested in seeing if there are any differences in how other penguin species, including Emperor penguins 
 (Aptenodytes forsteri) and Gentoo penguins (Pygoscelis papua), respond to climate change.

"There are many unanswered and interesting questions, which we are expecting to further investigate," the researchers said.

The team detailed their work today (Aug. 22) in the journal (and you can download the paper here) Scientific Reports.


Wednesday, August 14, 2013

Shortening Tails Gave Early Birds a Leg Up

This image shows fossil birds from the time of dinosaurs [left image: Eoenatiornis, right image: Hongshanornis] showing they had diverse types of legs. (Credit: Roger Close)
Aug. 13, 2013 — A radical shortening of their bony tails over 100 million years ago enabled the earliest birds to develop versatile legs that gave them an evolutionary edge, a new study shows.

A team led by Oxford University scientists examined fossils of the earliest birds from the Cretaceous Period, 145-66 million years ago, when early birds, such as Confuciusornis, Eoenantiornis, and Hongshanornis, lived alongside their dinosaur kin. At this point birds had already evolved powered flight, necessitating changes to their forelimbs, and the team investigated how this new lifestyle related to changes in their hind limbs (legs).

The team made detailed measurements of early bird fossils from all over the world including China, North America, and South America. An analysis of this data showed that the loss of their long bony tails, which occurred after flight had evolved, led to an explosion of diversity in the hind limbs of early birds, prefiguring the amazing variety of talons, stilts, and other specialised hind limbs that have helped to make modern birds so successful.

A report of the research is published this week in Proceedings of the Royal Society B.
'These early birds were not as sophisticated as the birds we know today -- if modern birds have evolved to be like stealth bombers then these were more like biplanes,' said Dr Roger Benson of Oxford University's Department of Earth Sciences, who led the research. 'Yet what surprised us was that despite some still having primitive traits, such as teeth, these early birds display an incredibly diverse array of versatile legs.'

By comparing measurements of the main parts of the legs of early birds -- upper leg, shin, and foot -- to those of their dinosaur relatives Dr Benson and co-author Dr Jonah Choiniere of the University of the Witwatersrand, South Africa, were able to determine whether bird leg evolution was exceptional compared to leg evolution in dinosaurs.

'Our work shows that, whilst they may have started off as just another type of dinosaur, birds quickly made a rather special evolutionary breakthrough that gave them abilities and advantages that their dinosaur cousins didn't have,' said Dr Rogers. 'Key to this special 'birdness' was losing the long bony dinosaur tail -- as soon as this happened it freed up their legs to evolve to become highly versatile and adaptable tools that opened up new ecological niches.'

It was developing these highly versatile legs, rather than powered flight, that saw the evolutionary diversification of early birds proceed faster than was generally true of other dinosaurs.

Story Source:
The above story is based on materials provided by University of Oxford, via EurekAlert!, a service of AAAS.
Note: Materials may be edited for content and length. For further information, please contact the source cited above.

University of Oxford (2013, August 13). Shortening tails gave early birds a leg up. ScienceDaily. Retrieved August 14, 2013, from­ /releases/2013/08/130813201426.htm

Tuesday, August 13, 2013

Protected area -- New ASPA site at Cape Washington conserves penguins, silverfish

Penguins jump out of the water.
Photo Credit: Dr. Paul Ponganis/Antarctic Photo Library
Emperor penguins leap out of the water near their colony at Cape Washington. The colony and a nearby silverfish nursery received special protection under the Antarctic Treaty earlier this year.

One of the world’s largest emperor penguin colonies and the first documented Antarctic silverfish nursery have been given special protection under the Antarctic Treaty System External Non-U.S. government site that governs the international management of the southernmost continent and surrounding region.

A 286-square-kilometer swath in the Ross Sea External U.S. government site, designated as Cape Washington and Silverfish Bay, became the 73rd Antarctic Specially Protected Area (ASPA) External Non-U.S. government site. The designation is given to sites with special environmental, scientific, historic, aesthetic and/or wilderness values. An ASPA requires a special permit to enter.

In the case of Cape Washington and Silverfish Bay, the ASPA encompasses an emperor colony that boasts as many as 20,000 breeding pairs, as well as a nursery and hatchery for silverfish, a herring-sized fish that is a key species in the Ross Sea food web. All but two percent of ASPA No. 173 is marine territory.

“I think it was important to create an ASPA for Cape Washington because it has the second, if not the largest, emperor penguin colony in the world,” said Dr. Paul Ponganis External Non-U.S. government site, “and also because an adjoining section of Terra Nova Bay is the only known nursery site of the Antarctic silverfish.
Map of a region in Antarctica.
Photo Credit: ERA
A map shows the Cape Washington and Silverfish Bay ASPA.
Snowy area punctuated by a few rocky areas.
Photo Credit: Dr. Paul Ponganis/Antarctic Photo Library
What appears to be dirty snow in this aerial photo of Cape Washington is actually the emperor penguin colony.
“Both are valuable biological sites worth preserving and protecting,” he added.

An anesthesiologist and marine biologist, Ponganis has studied Antarctica’s largest penguin species for more than 20 years, research first pioneered in the 1960s by his colleague at the University of California-San Diego’s Scripps Institution of Oceanography, Gerry Kooyman External Non-U.S. government site. [See previous article — A big breath; Study tackles emperor penguin diving physiology, population dynamics and even leopard seals.]

Both Ponganis and Kooyman provided advice and data for the proposed ASPA, which was officially adopted at the 36th Antarctic Treaty Consultative Meeting (ATCM) External Non-U.S. government site in Brussels, Belgium, in May of this year.

The Cape Washington colony competes with Coulman Island, also in the Ross Sea, as the largest emperor penguin colony in the world. The former represents about eight percent of the global emperor population and accounts for roughly a fifth of the Ross Sea population.

Emperor penguins, Aptenodytes forsteri, are the largest of 17 species. They are unique in their breeding habits, incubating a single egg throughout the Antarctic winter. The fat reserves of the male, in combination with a huddle strategy, help protect the males and their eggs through the winter when coastal temperatures can drop below minus 30 degrees Celsius.

No colony is more successful at breeding than the one at Cape Washington, which averages about 95 percent of chicks successfully fledged, according to one six-year study. Colonies in East Antarctica average around a 60 to 70 percent success rate.

About 20 kilometers west of Cape Washington is Silverfish Bay, where the first documented nursery and hatching area for Antarctic silverfish (Pleuragramma antarcticum) is located.

According to the ASPA description, recent research has shown that the concentration of spawning can extend all the way across the embayment to Cape Washington, with the first “ground-breaking” studies on the life history of this species taking place at the site.

One of the biggest challenges in designing the Cape Washington and Silverfish Bay ASPA involved protecting the site while still allowing access for tourists and personnel from nearby research stations, according to Colin Harris, director of Environmental Research & Assessment (ERA) External Non-U.S. government site. ERA helps prepare environmental documents and assessments on behalf of the National Science Foundation (NSF) External U.S. government site, which manages the U.S. Antarctic Program (USAP) External U.S. government site.

“Initially, we encountered considerable opposition to the proposal for this reason,” Harris explained by e-mail. “The boundaries needed to be designed in accordance with the environmental and scientific values, although this meant that visitors without a permit would be excluded from the breeding locality of the emperors.”

The compromise involved establishing a boundary that allows visitors to access sea ice in the vicinity of the main colony to view penguins but does not grant access to the core of the breeding area, which is usually centered about one kilometer northwest of the cape.

There are two research stations within the immediate vicinity. One is Mario Zucchelli External Non-U.S. government site, an Italian station that operates only during the summer months, from October to February. Nearby is also a summer-only German research station, Gondwana.

Photo Credit: Joel Bellucci
Antarctic silverfish
South Korea is currently building a year-round facility in the region that will house up to 60 in the summer after construction is complete next year. The Chinese have announced plans to establish a station on nearby Inexpressible Island.

In addition, the emperor colony has drawn a modest number of tourists for the last 20 years. Over the last decades, the site has averaged about 200 people each year. Nearly 35,000 tourists visited Antarctica in 2012-13, most visiting the Antarctic Peninsula, on the others side of the continent.

The size of the Cape Washington and Silverfish Bay ASPA is relatively modest compared to other specially protected areas, according to Harris.

“It was recognized that the emperors forage far beyond this limit, extending right across the Ross Sea, so it was decided to focus on the breeding area of the emperors, as well as the ‘nursery’ area of the silverfish in the context of the concentration of human activities in the vicinity,” he explained.
The Cape Washington ASPA also affords protection to a number of species that nest or forage within the ASPA.

A south polar skua colony of about 50 pairs of birds is located on the ice-free slopes of Cape Washington, overlooking the emperor colony. Snow petrels have been recorded as breeding in niches in the Cape Washington cliffs.

Leopard seal head pokes out of the water.
Photo Credit: Dr. Paul Ponganis/Antarctic Photo Library
A leopard seal prowls for prey near Cape Washington.
Adélie penguins have also been observed along the ice edge and within the emperor colony during summer months, while Wilson’s storm petrels are frequently observed along the ice edge from mid- to late-November. Southern giant petrels have been seen flying overhead.

Large pods of killer whales, with groups of up to 100 individuals, are regularly observed foraging around Cape Washington. Other whales spotted in the area include minke whales and Arnoux’s beaked whales.
Three species of seal — Weddell, leopard and crabeater — are also commonly seen in the area.

The United States has put forth 15 ASPAs over the years. Last year, the Antarctic Treaty nations adopted the first sub-aerial ASPA, Lower Taylor Glacier and Blood Falls ASPA 172 Link to PDF file, also proposed by the United States. [See previous article — Environmental precedent: Blood Falls becomes first subglacial ASPA to protect scientific values.]

Blood Falls External U.S. government site hosts a subglacial ecosystem that is home to a unique microbial community, which scientists believe has evolved over hundreds of thousands of years to subsist on a chemical soup of sulfur and iron compounds in the absence of oxygen and light. It’s the sort of conditions that might exist on another planet or moon, making it a valuable natural laboratory to study exobiology.
ASPA No. 173 will protect yet another natural laboratory where scientists can continue to study Antarctica’s unique ecosystem.

“I think the value of the Cape Washington ASPA is the recognition of the biological value of its larger emperor penguin colony and  the silverfish nursery, and, consequently, the value of ensuring preservation and protection of the region in the future,” Ponganis said.