OREGON STATE UNIVERSITY

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New study finds “saturation state” directly harmful to bivalve larvae

CORVALLIS, Ore. – The mortality of larval Pacific oysters in Northwest hatcheries has been linked to ocean acidification, yet the rate of increase in anthropogenic carbon dioxide in the atmosphere and the decrease of pH in near-shore waters have been questioned as being severe enough to cause the die-offs.

However, a new study of Pacific oyster and Mediterranean mussel larvae found that the earliest larval stages are directly sensitive to saturation state, not carbon dioxide (CO2) or pH. Saturation state is a measure of how corrosive seawater is to the calcium carbonate shells made by bivalve larvae, and how easy it is for larvae to produce their shells.

It is important to note that increasing CO2 lowers saturation state, the researchers say, and saturation state is very sensitive to CO2; the challenge interpreting previous studies is that saturation state and pH typically vary together with increasing CO2. The scientists utilized unique chemical manipulations of seawater to identify the direct sensitivity of larval bivalves to saturation state.

Results of the study, which was funded by the National Science Foundation, are being reported this week in the journal Nature Climate Change.

“Bivalves have been around for a long time and have survived different geologic periods of high carbon dioxide levels in marine environments,” said George Waldbusser, an Oregon State University marine ecologist and biogeochemist and lead author on the study, “The difference is that in the past, alkalinity levels buffered increases in CO2, which kept the saturation state higher relative to pH.”

“The difference in the present ocean is that the processes that contribute buffering to the ocean cannot keep pace with the rate of anthropogenic CO2 increase,” added Waldbusser, who is in Oregon State’s College of Earth, Ocean, and Atmospheric Sciences. “As long as the saturation state is high, the oysters and mussels we tested could tolerate CO2 concentrations almost 10 times what they are today.”

The idea that early bivalve development and growth is not as physiologically linked to CO2 or pH levels as previously thought initially seems positive. However, the reverse is actually true, Waldbusser noted. Larval oysters and mussels are so sensitive to the saturation state (which is lowered by increasing CO2) that the threshold for danger will be crossed “decades to centuries” ahead of when CO increases (and pH decreases) alone would pose a threat to these bivalve larvae.

“At the current rate of change, there is not much more room for the waters off the Oregon coast to absorb more CO2 without crossing the threshold we have identified with respect to saturation state,” he said. Results of the study help explain commercial hatchery failures and why improving water chemistry in those hatcheries has been successful.

What kept the system more balanced in the geologic past likely included a combination of factors, the researchers say. One factor in past increases of carbon dioxide was high levels of volcanic activity. However, greater volcanic activity also coincides with more tectonic plate activity and uplift, increasing the weathering of rock surfaces – and thus alkalinity in rivers, where it eventually flowed into the ocean to offset the CO2.

Computer models suggest that carbon dioxide is increasing through human activity some 100 to 1,000 times faster than the weathering processes that produce alkalinity can keep up, Waldbusser noted.

The Nature Climate Change study builds on previous research by Waldbusser and colleagues that outlined the mechanisms by which young bivalves create their shells after fertilization. In that study, the researchers found that young oysters and mussels had to build their shells within 48 hours to successfully begin feeding at a rate fast enough to survive, and that rate of shell-building would require a lot of energy. Thus in the presence of acidic water, they had to divert too much energy to shell-building and lacked the energy to swim and get food.

“The hatcheries call it the ‘lazy larvae syndrome’ because these tiny oysters just sink in the water and stop swimming,” Waldbusser said. “These organisms have really sensitive windows to ocean acidification – even more sensitive then we previously thought.”

In this latest study, the researchers used high-resolution images to analyze the development of oyster and mussel shells. They found that the organisms – which are about 1-100th the diameter of a human hair – actually build a complete calcium carbonate shell within six hours, about 12 hours after fertilization.

Throw off the ocean chemistry just a bit however, the researchers say, and a greater proportion of the shells do not develop normally. The ones that do are smaller, leading to potentially weaker organisms that will take longer to get to a size where they can settle into adult life.

“When the water is more saturated and has greater alkalinity it helps offset higher levels of carbon dioxide, ensuring that shell formation can proceed – and also making the shells bigger,” Waldbusser said. “This can have a significant impact on their survivability into the future.”

Shellfish hatcheries are altering their water chemistry based on the OSU research to create more favorable saturation state conditions for young bivalves; however this only helps organisms that can be cultured easily and increasing alkalinity in natural environments is a formidable challenge because of the amount required.

Other Oregon State researchers on the Nature Climate Change study included Burke Hales, Chris Langdon, Brian Haley, Paul Schrader, Elizabeth Brunner, Matthew Gray, Cale Miller and Iria Gimenez.

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George Waldbusser, 541-737-8964; waldbuss@coas.oregonstate.edu

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“Big Data” challenge seeks techie solution to science problem

NEWPORT, Ore. – Hatfield Marine Science Center researchers studying the marine food web have literally tens of millions of photographic images of small marine organisms called “plankton” to identify – a task that would take two lifetimes to finish manually.

Their hope is that the data science community can develop a computer algorithm that can do it automatically.

This week, Booz Allen Hamilton, a management and technology consultant firm, and Kaggle, the leading online data science competition community, announced the launch of the inaugural National Data Science Bowl to seek a solution to this “big data” challenge.

They are offering prize money totaling $175,000 to the creators of the top three algorithms – the largest such purse designated for a Kaggle competition benefitting social good. More information on the National Data Science Bowl is available at: http://www.datasciencebowl.com/

The 90-day competition will not only provide the data science community a chance to flex its creativity and brain power, it hopefully will solve a challenge facing marine science researchers who need to process massive amounts of data in hours, not decades. The winning algorithms will be donated to Oregon State University’s Hatfield Marine Science Center in Newport, Ore., for use by the scientific community.

“The National Data Science Bowl was born from the realization that, in order for the data science community to grow and thrive, it must be given opportunities to use its talents to benefit both business and society,” said Josh Sullivan, vice president of Booz Allen Hamilton’s Strategic Innovation Group. “We are extremely honored to partner with leaders such as Kaggle and the Hatfield Marine Science Center for this initiative.”

Robert Cowen, director of OSU’s Hatfield Marine Science Center, admits the task is daunting. In the summer of 2014, center researchers embarked on an 18-day expedition funded by the National Science Foundation to study interactions between larval fishes, their planktonic prey, and their predators in the Straits of Florida. With their specially designed imaging system, the In Situ Ichthyoplankton Imaging System (ISIIS), they collected 32 terabytes of images of plankton, fish and jellyfish.

That is an amount of data equivalent to 9 million MP3 songs, or enough music to listen to nonstop for 52 years.

Plankton are the fundamental biological building blocks of ocean ecosystems, yet scientists don’t know as much about them as they would like, including their diversity, interactions with other marine organisms, what triggers their blooms, and how they respond to climate change.

Advancing scientific knowledge about these tiny organisms begins with identifying and cataloguing them, Cowen pointed out.

“Many economically important animals – including fishes, crabs and other shellfish – are part of the plankton in their early life stages,” he said. “Much of what we study relates to understanding the relationship between larval fishes and their planktonic prey and predators.”

Ultimately, what scientists are interested in “is what drives variation in year-to-year population abundances of key fish species,” said Su Sponaugle, co-principle investigator on the project and a professor in the Department of Integrative Biology at OSU.

Jessica Luo, a doctoral student from the University of Miami’s Rosenstiel School of Marine and Atmospheric Sciences working with Cowen and Sponaugle at the Hatfield Center, said what the researchers need from the data science community is akin to “facial recognition” software for planktonic species.

“At a minimum, we’re aiming for an automatic classification system that can identify organisms to the class or order level, in general groups like fish or shrimps,” she said. “But with distinctly shaped or transparent organisms, we think it might be possible to get down to the genus or even species level. It will be difficult, because plankton are of all different sizes, shapes and orientations, and are moving in all different directions.”

Kelly Robinson, a post-doctoral researcher at the Hatfield Marine Science Center, said scientists would benefit greatly from an automated system that could provide near real-time data of plankton abundance and diversity while aboard ships.

“From a resource management perspective, it is less effective to analyze plankton abundance and diversity from four years earlier if the resource that depends on plankton responds rapidly to environmental change,” she said. “The current process of manually identifying organisms is time-consuming and laborious.  The ocean is changing rapidly and there is an urgency to learn as much as we can about plankton interrelationships to help ensure the health of our marine environments.”

For the competition, participants will be given access to nearly 100,000 underwater images and tasked with developing an algorithm that will identify and monitor them at a scale never before attempted. If successful, it will open up new doors to researchers and vastly improve the ability of resource managers to apply science to decision-making.

“The algorithms resulting from this competition will be applied to millions of images taken in a variety of marine environments, allowing cross-comparison and analysis at an unprecedented scale,” Cowen said.

Media Contact: 
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Bob Cowen, 541-867-0211; Robert.Cowen@oregonstate.edu;

Jessica Luo, 650-387-5700; Jessica.luo@rsmas@miami.edu;

Kelly Robinson, 253-232-3899, Kelly.robinson@oregonstate.edu

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No laughing matter: Nitrous oxide rose at end of last ice age

CORVALLIS, Ore. – Nitrous oxide (N2O) is an important greenhouse gas that doesn’t receive as much notoriety as carbon dioxide or methane, but a new study confirms that atmospheric levels of N2O rose significantly as the Earth came out of the last ice age and addresses the cause.

An international team of scientists analyzed air extracted from bubbles enclosed in ancient polar ice from Taylor Glacier in Antarctica, allowing for the reconstruction of the past atmospheric composition. The analysis documented a 30 percent increase in atmospheric nitrous oxide concentrations from 16,000 years ago to 10,000 years ago. This rise in N2O was caused by changes in environmental conditions in the ocean and on land, scientists say, and contributed to the warming at the end of the ice age and the melting of large ice sheets that then existed.

The findings add an important new element to studies of how Earth may respond to a warming climate in the future. Results of the study, which was funded by the U.S. National Science Foundation and the Swiss National Science Foundation, are being published this week in the journal Nature.

“We found that marine and terrestrial sources contributed about equally to the overall increase of nitrous oxide concentrations and generally evolved in parallel at the end of the last ice age,” said lead author Adrian Schilt, who did much of the work as a post-doctoral researcher at Oregon State University. Schilt then continued to work on the study at the Oeschger Centre for Climate Change Research at the University of Bern in Switzerland.

“The end of the last ice age represents a partial analog to modern warming and allows us to study the response of natural nitrous oxide emissions to changing environmental conditions,” Schilt added. “This will allow us to better understand what might happen in the future.”

Nitrous oxide is perhaps best known as laughing gas, but it is also produced by microbes on land and in the ocean in processes that occur naturally, but can be enhanced by human activity. Marine nitrous oxide production is linked closely to low oxygen conditions in the upper ocean and global warming is predicted to intensify the low-oxygen zones in many of the world’s ocean basins. N2O also destroys ozone in the stratosphere.

“Warming makes terrestrial microbes produce more nitrous oxide,” noted co-author Edward Brook, an Oregon State paleoclimatologist whose research team included Schilt. “Greenhouse gases go up and down over time, and we’d like to know more about why that happens and how it affects climate.”

Nitrous oxide is among the most difficult greenhouse gases to study in attempting to reconstruct the Earth’s climate history through ice core analysis. The specific technique that the Oregon State research team used requires large samples of pristine ice that date back to the desired time of study – in this case, between about 16,000 and 10,000 years ago.

The unusual way in which Taylor Glacier is configured allowed the scientists to extract ice samples from the surface of the glacier instead of drilling deep in the polar ice cap because older ice is transported upward near the glacier margins, said Brook, a professor in Oregon State’s College of Earth, Ocean, and Atmospheric Sciences.

The scientists were able to discern the contributions of marine and terrestrial nitrous oxide through analysis of isotopic ratios, which fingerprint the different sources of N2O in the atmosphere.

“The scientific community knew roughly what the N2O  concentration trends were prior to this study,” Brook said, “but these findings confirm that and provide more exact details about changes in sources. As nitrous oxide in the atmosphere continues to increase – along with carbon dioxide and methane – we now will be able to more accurately assess where those contributions are coming from and the rate of the increase.”

Atmospheric N2O was roughly 200 parts per billion at the peak of the ice age about 20,000 years ago then rose to 260 ppb by 10,000 years ago. As of 2014, atmospheric N2Owas measured at about 327 ppb, an increase attributed primarily to agricultural influences.

Although the N2O increase at the end of the last ice age was almost equally attributable to marine and terrestrial sources, the scientists say, there were some differences.

“Our data showed that terrestrial emissions changed faster than marine emissions, which was highlighted by a fast increase of emissions on land that preceded the increase in marine emissions,” Schilt pointed out. “It appears to be a direct response to a rapid temperature change between 15,000 and 14,000 years ago.”

That finding underscores the complexity of analyzing how Earth responds to changing conditions that have to account for marine and terrestrial influences; natural variability; the influence of different greenhouse gases; and a host of other factors, Brook said.

“Natural sources of N2O are predicted to increase in the future and this study will help up test predictions on how the Earth will respond,” Brook said.

Media Contact: 
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Adrian Schilt, schilta@science.oregonstate.edu;

Ed Brook, 541-737-8197, brooke@geo.oregonstate.edu

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Photo at left: Taylor Glacier in Antarctica

Scientists prepare for another wave of tsunami debris, possible invasives

NEWPORT, Ore. – Scientists monitoring incoming tsunami debris were taken aback last spring when some 30 fishing vessels from Japan washed ashore along the Pacific Northwest coast – many of them covered in living organisms indigenous to Asia.

Incidence of wayward skiffs and other tsunami debris subsequently declined sharply over the summer because of seasonal shifts in the winds. Now, those winds and currents have returned to their winter-spring pattern and scientists are expecting more items to wash ashore – even though it is nearing four years since a massive earthquake and tsunami shook Japan.

Blue mussels have been found on literally every boat that has washed ashore and some 200 different species overall have been documented on tsunami debris, according to John Chapman, an Oregon State University marine invasive species specialist at OSU’s Hatfield Marine Science Center.

“The crustaceans and bivalves are of particular concern because they could introduce new diseases, and compete with, displace or otherwise affect our oyster or mussel populations,” Chapman noted.

Just last week, a tote with numerous mussels washed up at Seal Rock – a sign that debris will still be arriving over the next few months. Of particular concern are boats and large objects that wash ashore carrying a variety of living organisms – including some new species that were not aboard the now-infamous dock that landed on Agate Beach near Newport, Ore., in June of 2012.

“We continue to find new organisms that we have never seen before,” Chapman said. “There isn’t as much diversity aboard the Japanese fishing vessels as there was on the dock, but each new species that we haven’t seen before is a cause for concern.

“No one can predict if these new species may gain a foothold in Northwest waters – and what impacts that may have,” he added.

Chapman and OSU colleague Jessica Miller have examined roughly a dozen boats that have washed ashore from the southern Oregon coast to the central Washington coast. Most of them were similar in style – long, narrow skiffs up to 30 feet in length, with no motors. As they drift from Asia to the West Coast of North America, they pick up a variety of organisms along the way.

“We’ve been surprised at the tenacity of some of these coastal Asian organisms that are arriving on the tsunami debris because the middle of the ocean isn’t the most biologically productive place for coastal species,” Miller said.

Among some of the species the Oregon State biologists have encountered over the past year are bat stars, which are sea stars that look like they have bat wings; striped knifejaw, fish that were found alive in at least one boat; and numerous small crustaceans.

Teams of scientists from around the North Pacific region, including Chapman and Miller, have identified more than 165 species that were aboard the original dock, and another 40-50 species that were found on other debris items, including boats. The rate of incoming debris should be slowing, the researchers say, but the arrival of so many boats last spring suggests that the threat is not over.

Invasive marine species are a problem on the West Coast, where they usually are introduced via ballast water from ships. OSU’s Chapman is well aware of the issue; for several years he has studied a parasitic isopod called Griffen’s isopod that was introduced from Asia. Griffen’s isopod infests mud shrimp in estuaries from California to Vancouver Island and is decimating their populations.

The OSU researchers are working with other scientists on the West Coast, who are attempting to genetically identify all of the species arriving on tsunami debris using genomic sampling – work led by Jon Geller of Moss Landing Marine Laboratory. Geller and his students also are collecting samples of marine life in Northwest coastal and estuary communities to look for evidence that non-native species may have established.

“We’re also doing a lot of old-fashioned looking,” Chapman said. “But new species can be difficult to identify if you aren’t searching for them directly in the first place. So we’ve identified three species that are particularly abundant in Asia, appear highly suited for invading the open coast, and would be readily apparent to searchers looking in the right place.”

These species include a hydroid, Eutima; a fly, Telmatogeton; and an amphipod crustacean, Caprella cristibrachium.

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John Chapman, 541-867-0235;

Jessica Miller, 541-867-0381

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OSU marine ecologist chosen as first U.S. Science Envoy for Oceans

WASHINGTON, D.C. – Building on a new commitment to improved marine protection and management, the U.S. Department of State has chosen Jane Lubchenco as the first Science Envoy for the Oceans.

Officials today named the fourth cohort of the U.S. Science Envoy Program, which was begun by President Obama in 2009. For the first time, one of the eminent scientists involved in the initiative has a specific focus on the world’s oceans.

Lubchenco is the University Distinguished Professor of Marine Biology at Oregon State University and former administrator of the National Oceanic and Atmospheric Administration. She is an international expert on marine ecology, environmental science and climate change.

“This new focus on the oceans is a strong statement by the Secretary of State and President Obama about the importance of our oceans to people around the world,” Lubchenco said. “They understand that science-based understanding, policy and management hold the key to a healthy, productive and resilient ocean, people and communities.”

Three other science envoys were also announced to focus on various nations and areas of expertise, including Geraldine Richmond, presidential chair and professor of chemistry at the University of Oregon.

In this program, these “envoys” travel internationally as private citizens, but will also advise and share their insights with the White House, U.S. Department of State and the U.S. science community about science-based collaboration, innovation and economic growth.

Lubchenco said her appointment builds on progress made earlier this year at the Our Ocean Conference led by Secretary of State John Kerry.

Noting that she was “deeply honored to be named to the position,” Lubchenco said she hopes to work with international colleagues to identify opportunities for science-based policies, building scientific capacity and exchanging findings.

“Around the world, the ocean is changing,” Lubchenco said. “Climate change, ocean acidification, overfishing, habitat destruction and pollution are all critical concerns. But we believe it’s possible to identify smart, science-based approaches that can help cope with many of these challenges.”

Science might help transform small-scale fisheries that are essential to the livelihoods and food security of millions of people into more sustainable and profitable fisheries, Lubchenco said. Marine protected areas could more effectively serve as “fish banks” to replenish fisheries, while also protecting habitats and biodiversity. And various steps could be taken to buffer against the forces of climate and other environmental changes.

“We haven’t yet decided on specific projects or regions,” Lubchenco said, “but we’re going to explore all the ways in which science can help create a healthy ocean, healthy people and a prosperous economy.

Lubchenco, who does research in the Department of Integrative Biology of the OSU College of Science, also said the new position will fit well with the Marine Studies Initiative at OSU, and provide opportunities for faculty and students to become more involved in new research and initiatives.

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 Jane Lubchenco, Lubchenco@oregonstate.edu

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Science study links greenhouse gases to African rainfall

CORVALLIS, Ore. – Scientists may have solved a long-standing enigma known as the African Humid Period – an intense increase in cumulative rainfall in parts of Africa that began after a long dry spell following the end of the last ice age and lasting nearly 10,000 years.

In a new study published this week in Science, an international research team linked the increase in rainfall in two regions of Africa thousands of years ago to an increase in greenhouse gas concentrations. The study was funded by the National Science Foundation and the U.S. Department of Energy.

The findings are critical, researchers say, because they provide new evidence that increases in carbon dioxide and other greenhouse gases could have a significant impact on the future climate of Africa.

“This study is important not only because it explains a long-standing puzzle, but it helps to validate model predictions of how rising greenhouse gas concentrations might change rainfall patterns in a highly populated and vulnerable part of the world,” said Peter Clark, an Oregon State University paleoclimatologist and co-author on the study.

The study was led by the National Center for Atmospheric Research (NCAR). It used computer simulations and analysis of geologic records of past climate.

The researchers focused on the era following the last ice age. When ice sheets covering North America and northern Europe began retreating after the last glacial maximum some 21,000 years ago, there was a long dry spell in central Africa that lasted until about 14,700 years ago, when rainfall increased abruptly. Scientists have long been puzzled by the regime shift, which turned deserts into grasslands and earned the African Humid Period moniker.

Rainfall actually increased in two separate regions of Africa – one north of the equator, the other south. Some previous studies had suggested that the shift may have been triggered by changes in the Earth’s orbit, but lead author Bette Otto-Bliesner said orbital patterns alone could not explain increased rainfall of that extent in both regions.

As the Earth emerged from the ice age, atmospheric levels of carbon dioxide and methane increased significantly – almost to pre-industrial levels – by 11,000 years ago. As the planet continued warming, ice sheets melted and the influx of fresh water from North America and northern Europe began weakening the Atlantic Meridional Overturning Circulation, which brings warm water up from the tropics and keeps Europe temperate.

This weakening of the Atlantic ocean current simultaneously moved precipitation southward toward the southernmost part of Africa, and suppressed rainfall in east Africa and northern equatorial Africa during the long dry spell, the researchers say.

When the ice sheets stopped melting, the circulation strengthened and brought precipitation back to the north. This change, coupled with the orbital shift and warming of both the atmosphere and oceans by greenhouse gases, triggered the African Humid Period.

“This study provides yet another demonstration of the sensitivity of the Earth’s climate to small changes in atmospheric greenhouse gases,” said Clark, a professor in OSU’s College of Earth, Ocean, and Atmospheric Sciences.

The science team recreated records of past moisture conditions by examining fossils, former lake levels and other geologic data, and simulated past climate with a power climate model developed by NCAR.

”The future impact of greenhouse gases on rainfall in Africa is a critical socioeconomic issue,” Otto-Bliesner said. “Africa’s climate seems destined to change, with far-reaching implications for water resources and agriculture in ways that may generate new conflicts.”

The study focused on the Sahel region of Africa to the north, including Niger, Chad and northern Nigeria; and the southeastern equatorial region of Africa, including the Democratic Republic of Congo, Rwanda, Burundi, Tanzania and Kenya.

Media Contact: 
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Peter Clark, 541-737-1247; clarkp@geo.oregonstate.edu

PNAS study: Ocean biota responds to global warming

CORVALLIS, Ore. – As the Earth warmed coming out of the last ice age, the rate of plankton production off the Pacific Northwest coast decreased, a new study has found, though the amount of organic material making its way to the deep ocean actually increased.

This suggests that during future climate warming, the ocean may be more efficient than previously thought at absorbing carbon dioxide from the atmosphere – at least in some regions – but raises new concerns about impacts on marine life.

Results of the study are being published online today in Proceedings of the National Academy of Sciences.

The ocean absorbs carbon dioxide like a sponge; scientists say that about one-third of all CO2   emitted historically by burning fossil fuels is now in the ocean. “This is a good news/bad news situation,” said Alan Mix, an Oregon State University oceanographer and co-author on the study. “It helps to slow the rise of CO2 in the atmosphere, but it makes the ocean more acidic.”

A major uncertainty has been how life in the ocean will respond to increasing CO2   and global warming. Growth of phytoplankton (microscopic plants such as diatoms) near the sea surface converts carbon dioxide into organic matter. When the plankton die, their organic remains either decompose in the surface ocean, or sink into the abyss.

This sinking of plankton effectively pumps CO2   out of the atmosphere. The so-called “biological pump” stores carbon in the deep sea, which is one way that biology influences global climate.

“It has been assumed that the amount of organic material that sinks to the sea floor would parallel that produced through photosynthesis near the sea surface,” said Mix, who is in OSU’s College of Earth, Ocean, and Atmospheric Sciences. “Surprisingly, our study found that even as plant growth decreased, past warming actually enhanced the biological export of carbon to the deep sea, at least in the northeast Pacific.”

Lead author Cristina Lopes, a visiting scientist at Oregon State who is based at the Instituto Português do Mar e da Atmosfera (IPMA, Portuguese Sea and Atmosphere Institute) in Portugal, and colleague Michal Kucera at the Center for Marine Environmental Sciences at Germany’s University of Bremen, calculated the productivity of marine plankton during the last major global warming event leading to the end of the last ice age. They did so by examining fossil diatoms buried in sediment off the coast of Oregon.

A breakthrough came from applying neural network methods now used by financial and insurance industries. “Inspired by brain research, we adapted these machine learning methods to analyze the fossil record for a new view of how the ocean works,” Kucera said.

The researchers found that during the ice age, the carbon trapped in plankton off Oregon was mostly recycled rather than exported to the deep ocean. As the ice age waned and the ocean warmed, plant growth decreased while carbon export increased.

“This counterintuitive effect was driven by a shift in ecosystems to one dominated by large diatoms,” Lopes said. “Those diatoms bloomed, then sank fast when they died.”

The researchers say their findings don’t necessarily mean that the ocean can continue to absorb increasing amounts of CO2   indefinitely, but that computer models of the ocean’s carbon cycle will need to take into account that plant productivity and carbon export are not always linked.

Evidence that export of carbon to the deep sea increases in some regions during long-term warming may help to slow down global climate change, but it may make some other impacts worse, the researchers point out. For example, as the extra sinking organic matter decomposes, it consumes oxygen dissolved in seawater – and loss of oxygen in the ocean is a growing concern.

Low-oxygen “dead zones” have appeared off the coast of Oregon several times in recent years.

“If these connections between warming and enhanced carbon export that we’ve found in past climate changes are triggered in the future, we can expect those marine dead zones to show up more frequently,” Mix said.

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Alan Mix, 541-737-5212, amix@coas.oregonstate.edu

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New study shows three abrupt pulse of CO2 during last deglaciation

CORVALLIS, Ore. – A new study shows that the rise of atmospheric carbon dioxide that contributed to the end of the last ice age more than 10,000 years ago did not occur gradually, but was characterized by three “pulses” in which C02 rose abruptly.

Scientists are not sure what caused these abrupt increases, during which C02 levels rose about 10-15 parts per million – or about 5 percent per episode – over a period of 1-2 centuries. It likely was a combination of factors, they say, including ocean circulation, changing wind patterns, and terrestrial processes.

The finding is important, however, because it casts new light on the mechanisms that take the Earth in and out of ice age regimes. Results of the study, which was funded by the National Science Foundation, appear this week in the journal Nature.

“We used to think that naturally occurring changes in carbon dioxide took place relatively slowly over the 10,000 years it took to move out of the last ice age,” said Shaun Marcott, lead author on the article who conducted his study as a post-doctoral researcher at Oregon State University. “This abrupt, centennial-scale variability of CO2 appears to be a fundamental part of the global carbon cycle.”

Some previous research has hinted at the possibility that spikes in atmospheric carbon dioxide may have accelerated the last deglaciation, but that hypothesis had not been resolved, the researchers say. The key to the new finding is the analysis of an ice core from the West Antarctic that provided the scientists with an unprecedented glimpse into the past.

Scientists studying past climate have been hampered by the limitations of previous ice cores. Cores from Greenland, for example, provide unique records of rapid climate events going back 120,000 years – but high concentrations of impurities don’t allow researchers to accurately determine atmospheric carbon dioxide records. Antarctic ice cores have fewer impurities, but generally have had lower “temporal resolution,” providing less detailed information about atmospheric CO2.

However, a new core from West Antarctica, drilled to a depth of 3,405 meters in 2011 and spanning the last 68,000 years, has “extraordinary detail,” said Oregon State paleoclimatologist Edward Brook, a co-author on the Nature study and an internationally recognized ice core expert. Because the area where the core was taken gets high annual snowfall, he said, the new ice core provides one of the most detailed records of atmospheric CO2.

“It is a remarkable ice core and it clearly shows distinct pulses of carbon dioxide increase that can be very reliably dated,” Brook said. “These are some of the fastest natural changes in CO2 we have observed, and were probably big enough on their own to impact the Earth’s climate.

“The abrupt events did not end the ice age by themselves,” Brook added. “That might be jumping the gun a bit. But it is fair to say that the natural carbon cycle can change a lot faster than was previously thought – and we don’t know all of the mechanisms that caused that rapid change.”

The researchers say that the increase in atmospheric CO2 from the peak of the last ice age to complete deglaciation was about 80 parts per million, taking place over 10,000 years. Thus, the finding that 30-45 ppm of the increase happened in just a few centuries was significant.

The overall rise of atmospheric carbon dioxide during the last deglaciation was thought to have been triggered by the release of CO2 from the deep ocean – especially the Southern Ocean. However, the researchers say that no obvious ocean mechanism is known that would trigger rises of 10-15 ppm over a time span as short as one to two centuries.

“The oceans are simply not thought to respond that fast,” Brook said. “Either the cause of these pulses is at least part terrestrial, or there is some mechanism in the ocean system we don’t yet know about.”

One reason the researchers are reluctant to pin the end of the last ice age solely on CO2 increases is that other processes were taking place, according to Marcott, who recently joined the faculty of the University of Wisconsin-Madison.

“At the same time CO2 was increasing, the rate of methane in the atmosphere was also increasing at the same or a slightly higher rate,” Marcott said. “We also know that during at least two of these pulses, the Atlantic Meridional Overturning Circulation changed as well. Changes in the ocean circulation would have affected CO2 – and indirectly methane, by impacting global rainfall patterns.”

“The Earth is a big coupled system,” he added, “and there are many pieces to the puzzle. The discovery of these strong, rapid pulses of CO2 is an important piece.”

Media Contact: 
Source: 

Shaun Marcott, smarcott@wisc.edu;

Ed Brook, 541-737-8197, brooke@geo.oregonstate.edu

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(Feature photo at left) - Donald Voigt from Penn State looks at an ice core in January 2012 during the WAIS Divide project. Photo courtesy of Gifford Wong, Dartmouth

 

 

 

 

 

 

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OSU scientists have examined air bubbles trapped in a new ice core that are providing them with some of the clearest indications of atmospheric conditions during the last ice age.

Study: Could sleeper sharks be preying on protected Steller sea lions?

NEWPORT, Ore. – Pacific sleeper sharks, a large, slow-moving species thought of as primarily a scavenger or predator of fish, may be preying on something a bit larger – protected Steller sea lions in the Gulf of Alaska.

A new study found the first indirect evidence that this cold-blooded shark that can grow to a length of more than 20 feet – longer than a great white shark – may be an opportunistic predator of juvenile Steller sea lions.

Results of the study have just been published in the journal Fishery Bulletin. The findings are important, scientists say, because of management implications for the protected Steller sea lions.

For the past decade, Markus Horning of the Marine Mammal Institute at Oregon State University has led a project in collaboration with Jo-Ann Mellish of the Alaska SeaLife Center to deploy specially designed “life history transmitters” into the abdomens of juvenile Steller sea lions. These buoyant archival tags record data on temperature, light and other properties during the sea lions’ lives and after the animals die the tags float to the surface or fall out ashore and transmit data to researchers via satellite.

From 2005-11, Horning and his colleagues implanted tags into 36 juvenile Steller sea lions and over a period of several years, 17 of the sea lions died. Fifteen transmitters sent data indicating the sea lions had been killed by predation.

“The tags sense light and air to which they are suddenly exposed, and record rapid temperature change,” said Horning, who is in OSU’s Department of Fisheries and Wildlife. “That is an indication that the tag has been ripped out of the body, though we don’t know what the predator is that did this.

“At least three of the deaths were different,” he added. “They recorded abrupt temperature drops, but the tags were still dark and still surrounded by tissue. We surmise that the sea lions were consumed by a cold-blooded predator because the recorded temperatures aligned with the deep waters of the Gulf of Alaska and not the surface waters.

“We know the predator was not a killer whale, for example, because the temperatures would be much higher since they are warm-blooded animals.” Data collected from the transmitters recorded temperatures of 5-8 degrees Celsius.

That leaves a few other suspects, Horning said. However, two known predators of sea lions – great white sharks and salmon sharks – have counter-current heat exchanges in their bodies that make them partially warm-blooded and the tags would have reflected higher temperatures.

By process of elimination, Horning suspects sleeper sharks.

The Oregon State pinniped specialist acknowledges that the evidence for sleeper sharks is indirect and not definitive, thus he is planning to study them more closely beginning in 2015. The number of sleeper sharks killed in Alaska as bycatch ranges from 3,000 to 15,000 annually, indicating there are large numbers of the shark out there. The sleeper sharks caught up in the nets are usually comparatively small; larger sharks are big enough to tear the fishing gear and are rarely landed.

“If sleeper sharks are involved in predation, it creates something of a dilemma,” said Horning, who works out of OSU’s Hatfield Marine Science Center in Newport, Ore. “In recent years, groundfish harvests in the Gulf of Alaska have been limited in some regions to reduce the potential competition for fish that would be preferred food for Steller sea lions.

“By limiting fishing, however, you may be reducing the bycatch that helps keep a possible limit on a potential predator of the sea lions,” he added. “The implication could be profound, and the net effect of such management actions could be the opposite of what was intended.”

Other studies have found remains of Steller sea lions and other marine mammals in the stomachs of sleeper sharks, but those could have been the result of scavenging instead of predation, Horning pointed out.

The western distinct population of Steller sea lions has declined to about 20 percent of the levels they were at prior to 1975.

Media Contact: 
Source: 

Markus Horning, 541-867-0270, markus.horning@oregonstate.edu

Scientists discover carbonate rocks are unrecognized methane sink

CORVALLIS, Ore. – Since the first undersea methane seep was discovered 30 years ago, scientists have meticulously analyzed and measured how microbes in the seafloor sediments consume the greenhouse gas methane as part of understanding how the Earth works.

The sediment-based microbes form an important methane “sink,” preventing much of the chemical from reaching the atmosphere and contributing to greenhouse gas accumulation. As a byproduct of this process, the microbes create a type of rock known as authigenic carbonate, which while interesting to scientists was not thought to be involved in the processing of methane.

That is no longer the case. A team of scientists has discovered that these authigenic carbonate rocks also contain vast amounts of active microbes that take up methane. The results of their study, which was funded by the National Science Foundation, were reported today in the journal Nature Communications.

“No one had really examined these rocks as living habitats before,” noted Andrew Thurber, an Oregon State University marine ecologist and co-author on the paper. “It was just assumed that they were inactive. In previous studies, we had seen remnants of microbes in the rocks – DNA and lipids – but we thought they were relics of past activity. We didn’t know they were active.

“This goes to show how the global methane process is still rather poorly understood,” Thurber added.

Lead author Jeffrey Marlow of the California Institute of Technology and his colleagues studied samples from authigenic compounds off the coasts of the Pacific Northwest (Hydrate Ridge), northern California (Eel River Basin) and central America (the Costa Rica margin). The rocks range in size and distribution from small pebbles to carbonate “pavement” stretching dozens of square miles.

“Methane-derived carbonates represent a large volume within many seep systems and finding active methane-consuming archaea and bacteria in the interior of these carbonate rocks extends the known habitat for methane-consuming microorganisms beyond the relatively thin layer of sediment that may overlay a carbonate mound,” said Marlow, a geobiology graduate student in the lab of Victoria Orphan of Caltech.

These assemblages are also found in the Gulf of Mexico as well as off Chile, New Zealand, Africa, Europe – “and pretty much every ocean basin in the world,” noted Thurber, an assistant professor (senior research) in Oregon State’s College of Earth, Ocean, and Atmospheric Sciences.

The study is important, scientists say, because the rock-based microbes potentially may consume a huge amount of methane. The microbes were less active than those found in the sediment, but were more abundant – and the areas they inhabit are extensive, making their importance potential enormous. Studies have found that approximately 3-6 percent of the methane in the atmosphere is from marine sources – and this number is so low due to microbes in the ocean sediments consuming some 60-90 percent of the methane that would otherwise escape.

Now those ratios will have to be re-examined to determine how much of the methane sink can be attributed to microbes in rocks versus those in sediments. The distinction is important, the researchers say, because it is an unrecognized sink for a potentially very important greenhouse gas.

“We found that these carbonate rocks located in areas of active methane seeps are themselves more active,” Thurber said. “Rocks located in comparatively inactive regions had little microbial activity. However, they can quickly activate when methane becomes available.

“In some ways, these rocks are like armies waiting in the wings to be called upon when needed to absorb methane.”

The ocean contains vast amounts of methane, which has long been a concern to scientists. Marine reservoirs of methane are estimated to total more than 455 gigatons and may be as much as 10,000 gigatons carbon in methane. A gigaton is approximate 1.1 billion tons.

By contrast, all of the planet’s gas and oil deposits are thought to total about 200-300 gigatons of carbon.

Media Contact: 
Source: 

Andrew Thurber, 541-737-4500, athurber@coas.oregonstate.edu