Antarctic penguin colony repeatedly decimated by volcanic eruptions

One of the largest colonies of gentoo penguins in Antarctica was decimated by volcanic eruptions several times during the last 7,000 years according to a new study. An international team of researchers, led by British Antarctic Survey (BAS), studied ancient penguin guano and found the colony came close to extinction several times due to ash fall from the nearby Deception Island volcano. Their results are published in Nature Communications.

Gentoo penguins climbing slopes to the nesting colony on Ardley Island 
[Credit: Stephen Roberts]

Ardley Island, near the Antarctic Peninsula, is currently home to a population of around 5,000 pairs of gentoo penguins. Using new chemical analyses of penguin guano extracted in sediment cores from a lake on the island, the researchers unraveled the history of the penguin colony.

Climate conditions around Ardley Island have been generally favourable for penguins over the last 7,000 years and the team had expected the local population to show minor fluctuations in response to changes in climate or sea ice. The surprising result was that the nearby Deception Island volcano had a far greater impact than originally anticipated.

Lead author Dr Steve Roberts from BAS says: "When we first examined the sediment cores we were struck by the intense smell of the guano in some layers and we could also clearly see the volcanic ash layers from nearby Deception Island. By measuring the sediment chemistry, we were able to estimate the population numbers throughout the period and see how penguins were affected by the eruptions.

Volcanic ash layers in lake sediment cores extracted from Kiteschee Lake on Fildes Peninsula. The ash layers shown are 
associated with comparatively small eruptions from Deception Island in the last c. 2000-3000 years. The largest 
eruptions preserved in our lake sediment records from Fildes Peninsula and Ardley Island occurred at c. 7,000 years 
ago and c. 5,500-4,500 years ago and deposited over a metre of airfall and reworked ash in some lake sediment cores 
[Credit: Stephen Roberts and Emma Pearson]

On at least three occasions during the past 7,000 years, the penguin population was similar in magnitude to today, but was almost completely wiped out locally after each of three large volcanic eruptions. It took, on average, between 400 and 800 years for it to re-establish itself sustainably."

Dr Claire Waluda, penguin ecologist from BAS says: "This study reveals the severe impact volcanic eruptions can have on penguins, and just how difficult it can be for a colony to fully recover. An eruption can bury penguin chicks in abrasive and toxic ash, and whilst the adults can swim away, the chicks may be too young to survive in the freezing waters. Suitable nesting sites can also be buried, and may remain uninhabitable for hundreds of years."

The techniques developed in this study will help scientists to reconstruct past changes in colony size and potentially predict how other penguin populations may be affected elsewhere. For example, the chinstrap penguins on Zavodovski Island, which were disturbed by eruptions from the Mt Curry volcano in 2016.

Waluda continues: "Changes in penguin populations on the Antarctic Peninsula have been linked to climate variability and sea-ice changes, but the potentially devastating long-term impact of volcanic activity has not previously been considered."

Source: British Antarctic Survey [April 11, 2017]

byUnknown

in Antarctic, Earth Science, Ecosystems, Natural Heritage, Wildlife

April 11, 2017

Antarctic penguin colony repeatedly decimated by volcanic eruptions

One of the largest colonies of gentoo penguins in Antarctica was decimated by volcanic eruptions several times during the last 7,000 years a...

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Scientists publish study on glacial carbon cycle

Two Montana State University researchers have played a major role in discovering how microbial communities in melting glaciers contribute to the Earth's carbon cycle, a finding that has global implications as the bulk of Earth's glaciers shrink in response to a warming climate.

The Cotton Glacier stream in the McMurdo Dry Valleys region of Antarctica, where MSU researchers 
Heidi Smith and Christine Foreman sampled glacier runoff in 2012, in shown in this aerial photo 
[Credit: Christine Foreman]

Heidi Smith, a postdoctoral researcher, and Christine Foreman, associate professor of chemical and biological engineering, both of the Center for Biofilm Engineering in MSU's College of Engineering, were co-authors of a paper published in the prestigious journal Nature Geoscience.

Titled "Microbial formation of labile organic carbon in Antarctic glacial environments," the article was co-authored by researchers at the University of Colorado at Boulder, the U.S. Geological Survey, Stockholm University in Sweden and the Max Planck Institute for Marine Microbiology in Germany.

The paper challenges the prevailing theory that microorganisms found in glacial meltwater primarily consume ancient organic carbon that was once deposited on glacial surfaces and incorporated into ice as glaciers formed.

"We felt that there was another side to the story," said Smith, the paper's lead author. Smith earned a Ph.D. in ecology and environmental sciences in MSU's Department of Land Resources and Environmental Sciences in 2016, with Foreman as her adviser.

"What we showed for the first time is that a large proportion of the organic carbon is instead coming from photosynthetic bacteria" that are also found in the ice and that become active as the ice melts, Smith said. Like plants, those bacteria absorb carbon dioxide and in turn provide a source of organic matter.

The research team made the discovery after sampling meltwater from a large stream flowing over the surface of a glacier in the McMurdo Dry Valleys region of Antarctica in 2012.

Afterward, Smith spent two months at the Max Planck Institute for Marine Microbiology in Bremen, Germany, with support from the National Science Foundation's flagship interdisciplinary training program, the Integrative Graduate Education and Research Traineeship. There, she worked with colleagues to track how different carbon isotopes moved through the meltwater's ecosystem, allowing the team to determine the carbon's origin and activity.

The researchers ultimately found that the glacial microbes utilized the carbon produced by the photosynthetic bacteria at a greater rate than the older, more complex carbon molecules deposited in the ice, because the bacterial carbon is more "labile," or easily broken down. The labile carbon "is kind of like a Snickers bar," meaning that it's a quick, energizing food source that's most available to the microbes, Smith said.

Moreover, the researchers found that the photosynthetic bacteria produced roughly four times more carbon than was taken up by the microbes, resulting in an excess of organic carbon being flushed downstream. "The ecological impact of this biologically produced organic carbon on downstream ecosystems will be amplified due to its highly labile nature," Foreman said.

Although individual glacial streams export relatively small amounts of organic carbon, the large mass of glaciers, which cover more than 10 percent of the Earth's surface, means that total glacial runoff is an important source of the material. Marine organic carbon underpins wide-ranging ecological processes such as the production of phytoplankton, the foundation of the oceans' food web.

As glaciers increasingly melt and release the organically produced, labile carbon, "we think that marine microbial communities will be most impacted," Smith said. "We hope this generates more discussion."

In a "News and Views" commentary accompanying the article in Nature Geoscience, Elizabeth Kujawinski, a tenured scientist at Woods Hole Oceanographic Institution, called the team's work "an elegant combination" of research methods.

Taken together with another study published in the same issue of Nature Geoscience, about microbial carbon cycling in Greenland, Smith's paper "deflates the notion that glacier surfaces are poor hosts for microbial metabolism," according to Kujawinski. The two studies "have established that microbial carbon cycling on glacier surfaces cannot be ignored," she added.

Source: Montana State University [April 04, 2017]

byUnknown

in Antarctic, Biology, Climate Change, Ecosystems, Environment, Natural Heritage

April 04, 2017

Scientists publish study on glacial carbon cycle

Two Montana State University researchers have played a major role in discovering how microbial communities in melting glaciers contribute to...

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