OREGON STATE UNIVERSITY

marine science and the coast

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: 
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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.

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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.

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

Anglers, beachcombers asked to watch for transponders from Japan

CORVALLIS, Ore. – Northwest anglers venturing out into the Pacific Ocean in pursuit of salmon and other fish this fall may scoop up something unusual into their nets – instruments released from Japan called “transponders.”

These floating instruments are about the size of a 2-liter soda bottle and were set in the ocean from different ports off Japan in 2011-12 after the massive Tohoku earthquake and tsunami. Researchers from Tattori University for Environmental Studies in Japan have been collaborating with Oregon State University, Oregon Sea Grant, and the NOAA Marine Debris Program on the project.

The researchers’ goal is to track the movement of debris via ocean currents and help determine the path and timing of the debris from the 2011 disaster. An estimated 1.5 million tons of debris was washed out to sea and it is expected to continue drifting ashore along the West Coast of the United States for several years, according to Sam Chan, a watershed health specialist with Oregon State University Extension and Oregon Sea Grant.

“These transponders only have a battery life of about 30 months and then they no longer communicate their location,” Chan said. “So the only way to find out where they end up is to physically find them and report their location. That’s why we need the help of fishermen, beachcombers and other coastal visitors.

“These bottles contain transmitters and they are not a hazardous device,” Chan added. “If you find something that looks like an orange soda bottle with a short antenna, we’d certainly like your help in turning it in.”

Persons who find a transponder are asked to photograph it if possible, and report the location of their find to Chan at Samuel.Chan@oregonstate.edu; or to the NOAA Marine Debris Program regional coordinator in their area at http://marinedebris.noaa.gov/contact-us. They will provide shipping instructions to persons who find the transponders so that the instruments can be returned to the research team.

One of the first transponders discovered in the Northwest washed ashore near Arch Cape, Oregon, in March 2013, about 19 months after it was set adrift. The persons who found it reported it to Chan, who began collaborating with researchers in Japan.

Another transponder was found near the Haida Heritage Site, formerly the Queen Charlotte Islands – the same location where a Harley-Davidson motorcycle floated up on a beach in a shipping container long after being swept out to sea in Japan by the tsunami.

“These transponders have recorded a lot of important data that will help us better understand the movement of tsunami and marine debris throughout the Pacific Ocean,” Chan said. “Everyone’s help in recovering these instruments is greatly appreciated.”

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Sam Chan, 541-737-4828; samuel.chan@oregonstate.edu

OSU part of major grant to study Southern Ocean carbon cycle

CORVALLIS, Ore. – A new six-year, $21 million initiative funded by the National Science Foundation will explore the role of carbon and heat exchanges in the vast Southern Ocean – and their potential impacts on climate change.

The Southern Ocean Carbon and Climate Observations and Modeling program will be headquartered at Princeton University, and include researchers at several institutions, including Oregon State University. It is funded by NSF’s Division of Polar Programs, with additional support from the National Oceanic and Atmospheric Administration and NASA.

The Southern Ocean acts as a carbon “sink” by absorbing as much as half of the human-derived carbon in the atmosphere and much of the planet’s excess heat. Yet little is known of this huge body of water that accounts for 30 percent of the world’s ocean area.

Under this new program known by the acronym SOCCOM, Princeton and 10 partner institutions will create a physical and biogeochemical portrait of the ocean using hundreds of robotic floats deployed around Antarctica. The floats, which will be deployed over the next five years, will collect seawater profiles using sophisticated sensors to measure pH, oxygen and nitrate levels, temperature and salinity – from the ocean surface to a depth of 1,000 meters, according to Laurie Juranek, an Oregon State University oceanographer and project scientist.

“This will be the first combined large-scale observational and modeling program of the entire Southern Ocean,” said Juranek, who is in OSU’s College of Earth, Ocean, and Atmospheric Sciences. “It is a very important region, but difficult to access – hence the use of robotic floats to collect data. However, not everything that we need to know can be measured by sensors, so we’ll need to get creative.”

Juranek's role in this project is to develop relationships between the measured variables and those that can't be measured directly by a sensor but are needed for understanding Southern Ocean carbon dioxide exchanges. These relationships can be applied to the float data as well as to high-resolution models. To do this work she is partnering with colleagues at NOAA's Pacific Marine Environmental Laboratory.

In addition to its role in absorbing carbon and heat, the Southern Ocean delivers nutrients to lower-latitude surface waters that are critical to ocean ecosystems around the world, said program director Jorge Sarmiento, Princeton's George J. Magee Professor of Geoscience and Geological Engineering and director of the Program in Atmospheric and Oceanic Sciences. And as levels of carbon dioxide increase in the atmosphere, models suggest that the impacts of ocean acidification are projected to be most severe in the Southern Ocean, he added.

"The scarcity of observations in the Southern Ocean and inadequacy of earlier models, combined with its importance to the Earth's carbon and climate systems, means there is tremendous potential for groundbreaking research in this region," Sarmiento said.

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Laurie Juranek, 541-737-2368; ljuranek@coas.oregonstate.edu

Study: Pacific Northwest shows warming trend over past century-plus

CORVALLIS, Ore. – The annual mean temperature in the Pacific Northwest has warmed by about 1.3 degrees Fahrenheit since the early 20th century – a gradual warming trend that has been accelerating over the past 3-4 decades and is attributed to anthropogenic, or human, causes.

The study is one of the first to isolate the role of greenhouse gases associated with regional warming, the authors say. It was published in a recent issue of the Journal of Climate, a publication of the American Meteorological Society.

“The amount of warming may not sound like a lot to the casual observer, but we already are starting to see some of the impacts and what is particularly significant is that the rate of warming is increasing,” said Philip Mote, director of the Oregon Climate Change Research Institute at Oregon State University and a co-author on the study.

“Just a 1.3-degree increase has lengthened the ‘freeze-free’ season by 2-3 weeks and is equivalent to moving the snowline 600 feet up the mountain,” Mote added. “At the rate the temperature is increasing, the next 1.3-degree bump will happen much more quickly.”

In their study, the researchers looked at temperatures and precipitation from 1901 to 2012 in the Northwest, which includes Washington, Oregon, Idaho, western Montana, and the northwestern tip of Wyoming. They examined four different factors to determine the influence of human activities, including greenhouse gases and aerosols; solar cycles; volcanic eruptions; and naturally occurring phenomena including El Niño events and the Pacific Decadal Oscillation.

Using what is called a “multilinear regression” approach, they were able to tease out the influences of the different factors. Volcanic activity, for example, led to cooler temperatures in 1961, 1982 and 1991. Likewise, El Niño events led to warming in numerous years.

“Natural variation can explain much of the change from year to year, but it cannot account for this long-term warming trend,” noted David Rupp, a research associate with the Oregon Climate Change Research Institute and co-author on the report. “Anthropogenic forcing was the most significant predictor of, and leading contributor to, the warming.”

Among the study’s findings:

  • The Northwest experienced relatively cool periods from 1910-25 and from 1945-60, and a warm period around 1940 and from the mid-1980s until the present.
  • The warmest 10-year period has been from 1998 to 2007, and very few years since 1980 have had below average annual mean temperatures.
  • The most apparent warming trend is in the coldest night of the year, which has warmed significantly in recent decades.
  • The only cooling trend the study documented was for spring temperatures the last three decades and is tied to climate variability and increasing precipitation during those spring months.

“The spring has been robustly wetter,” Mote said, “and that has brought some cooler temperatures for a couple of months. But it has been drier in the fall and winter, and the warming in fall and winter has been steepest since the 1970s.”

Lead author John Abatzoglou of the University of Idaho said that the study ties the warming trend to human activities.

“Climate is a bit like a symphony where different factors like El Niño, solar variability, volcanic eruptions and manmade greenhouse emissions all represent different instruments,” Abatzoglou said. “At regional scales like in the Northwest, years or decades can be dominated by natural climate variability, thereby muffling or compounding the tones of human-induced warming.

“Once you silence the influence of natural factors,” he said, “the signal of warming due to human causes is clear – and it is only getting louder.”

The researchers also explored but were unable to find any link between warming in the Northwest over the past century and solar variability.

A major concern, the authors say, is that the warming seems to be increasing.

“Climate is complex and you can get significant variations from year to year,” Mote said. “You have to step back and look at the big picture of what is happening over time. Clearly the Northwest, like much of the world, is experiencing a warming pattern that isn’t likely to change and, in fact, is accelerating.

“At this rate, the chance of the temperature only going up 1.3 degrees in the next century is close to zero.”

The study was funded by the U.S. Department of Agriculture and the National Oceanic and Atmospheric Administration.

Media Contact: 
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Phil Mote, 541-913-2274, philip.mote@coas.oregonstate.edu

David Rupp, 541-737-5222, David.Rupp@oregonstate.edu

John Abatzoglou, jabatzoglous@uidaho.edu, 208-885-6239

Study provides new look at ancient coastline, pathway for early Americans

CORVALLIS, Ore. – The first humans who ventured into North America crossed a land bridge from Asia that is now submerged beneath the Bering Sea, and then may have traveled down the West Coast to occupy sites in Oregon and elsewhere as long as 14,000 to 15,000 years ago.

Now a new study has found that the West Coast of North America may have looked vastly different than scientists previously thought, which has implications for understanding how these early Americans made this trek.

The key to this new look at the West Coast landscape is a fresh approach to the region’s sea level history over the last several thousand years. Following the peak of the last ice age about 21,000 years ago, the large continental ice sheets began to retreat, causing sea levels to rise by an average of about 430 feet. When the ice was prominent and sea levels were lower, large expanses of the continental shelf that today are submerged were then exposed.

As the melting progressed and sea levels rose, likely archaeological sites along the coast were submerged.

Most past models have assumed that as the massive North American ice sheets melted, global sea levels rose in concert – a phenomenon known as “the bathtub model.” But the authors of this new study, which was just published in the Journal of Archaeological Science, say sea level rise does not happen uniformly.

“During the last deglaciation, sea level rise was significantly influenced by the weight of the large ice sheets, which depressed the land under and near the ice sheets,” said Jorie Clark, a courtesy professor at Oregon State University and lead author on the study. “As the ice sheets melted, this land began to rise. At the same time, the weight of the water melting from the ice sheets and returning to the oceans also depressed the ocean basins.

“This exchange of mass between ice sheets and oceans led to significant differences in sea level at any given location from the assumption of a uniform change,” she added.

The implications of this new approach are significant. The researchers ran models of what the sea level may have looked like over the last 20,000 years – based on knowledge of ice sheet dimensions and the topography of the ocean floor – and concluded that parts of the West Coast looked radically different than previous reconstructions based on a model of uniform sea level rise.

The central Oregon shelf, for example, was thought to be characterized by a series of small islands some 14,000 years ago. However, the models run by Clark and her colleagues suggest that much of the continental shelf was exposed as a solid land mass, creating an extensive coastline. In some areas, the change in estimated sea level may have been as much as 100 feet.

 “There has been new evidence that the peopling of the Americas happened earlier than was long thought to be the case, which has put a lot of focus on coastal paleogeography,” said Clark, who is in OSU’s College of Earth, Ocean, and Atmospheric Sciences. “This new look at sea level changes helps explain how that earlier introduction into the Americas could be possible.”

 “It is also important for predicting where coastal villages that are now submerged on the continental shelf may be located.”

 Other authors on the study were Jerry Mitrovica of Harvard University, and Jay Alder of the U.S. Geological Survey.

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Jorie Clark, 541-737-1575; clarkjc@geo.oregonstate.edu

OSU researchers tagging whales off southern California

NEWPORT, Ore. – Oregon State University researchers are tagging blue and fin whales off the coast of southern California this summer to study their movements, some of which include preferred feeding grounds near areas of heavy ship traffic.

The project, which is being funded by the U.S. Navy, will build on a previous study by OSU researchers that documented the seasonal distribution of blue whales, including their appearance near established shipping lanes off Santa Barbara. That analysis was based on satellite tracking of 171 blue whales for up to 13 months during a 15-year stretch from 1993 to 2008.

It was published last month in the journal PLOS ONE. Since that publication, six major shipping companies voluntarily agreed to slow their ships near Santa Barbara to lessen the chance of striking endangered blue whales, and to reduce pollution.

“No one wants to see whales hit by ships, and it is clear from the analysis that there has been some historic overlap of blue whale feeding areas and shipping lanes,” said Bruce Mate, director of Oregon State University’s Marine Mammal Institute, which is conducting the tagging project. “The goal of the new Navy-funded project is to better understand the seasonal occurrence of blue and fin whales in southern California and determine if that overlap is still taking place for these protected species.”

An OSU team led by Ladd Irvine began tagging the whales last month and thus far has successfully deployed 21 tags. The researchers hope to attach 24 long-term satellite tracking tags – a dozen each for blue whales and fin whales – and another eight more sophisticated tags that will track the whales’ underwater feeding habits. They hope to attach four of these Advanced-Dive-Behavior tags on blue whales and four on fin whales.

OSU’s recently published 15-year analysis was the most comprehensive study of blue whales movements ever conducted. It tracked the movement of blue whales off the West Coast to identify important habitat areas and environmental correlates, and subsequently to understand the timing of their presence near major ports and shipping traffic.

“The main areas that attract blue whales are highly productive, strong upwelling zones that produce large amounts of krill – which is pretty much all that they eat,” said Irvine, who was lead author on the PLOS ONE study. “The whales have to maximize their food intake during the summer before they migrate south for the winter, typically starting in mid-October to mid-November. It appears that two of their main foraging areas are coincidentally crossed by shipping lanes.”

An estimated 2,500 of the world’s 10,000 blue whales spend time in the waters off the West Coast of the Americas and are known as the eastern North Pacific population. Blue whales can grow to the length of a basketball court, weigh as much as 25 large elephants combined, and their mouths could hold 100 people, though their diet is primarily krill – tiny shrimp-like creatures less than two inches in length.

At a distance, fin whales look a lot like blue whales. They are the second largest of the whales and reach 75 feet in length – the size of two buses. The tall, columnar blows of fin whales look much like that of blue whales. Fin whales have a taller, sickle-shaped dorsal fin, a lower right lip that is white, and feed on schooling fish as well as krill.

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Bruce Mate, 541-867-0202; bruce.mate@oregonstate.edu

Science study: Sunlight, not microbes, key to CO2 in Arctic

CORVALLIS, Ore. – The vast reservoir of carbon stored in Arctic permafrost is gradually being converted to carbon dioxide (CO2) after entering the freshwater system in a process thought to be controlled largely by microbial activity.

However, a new study – funded by the National Science Foundation and published this week in the journal Science – concludes that sunlight and not bacteria is the key to triggering the production of CO2 from material released by Arctic soils.

The finding is particularly important, scientists say, because climate change could affect when and how permafrost is thawed, which begins the process of converting the organic carbon into CO2.

“Arctic permafrost contains about half of all the organic carbon trapped in soil on the entire Earth – and equals an amount twice of that in the atmosphere,” said Byron Crump, an Oregon State University microbial ecologist and co-author on the Science study. “This represents a major change in thinking about how the carbon cycle works in the Arctic.”

Converting soil carbon to carbon dioxide is a two-step process, notes Rose Cory, an assistant professor of earth and environmental sciences at the University of Michigan, and lead author on the study. First, the permafrost soil has to thaw and then bacteria must turn the carbon into greenhouse gases – carbon dioxide or methane. While much of this conversion process takes place in the soil, a large amount of carbon is washed out of the soils and into rivers and lakes, she said.

“It turns out, that in Arctic rivers and lakes, sunlight is faster than bacteria at turning organic carbon into CO2,” Cory said. “This new understanding is really critical because if we want to get the right answer about how the warming Arctic may feedback to influence the rest of the world, we have to understand the controls on carbon cycling.

“In other words, if we only consider what the bacteria are doing, we’ll get the wrong answer about how much CO2 may eventually be released from Arctic soils,” Cory added.

The research team measured the speed at which both bacteria and sunlight converted dissolved organic carbon into carbon dioxide in all types of rivers and lakes in the Alaskan Arctic, from glacial-fed rivers draining the Brooks Range to tannin-stained lakes on the coastal plain. Measuring these processes is important, the scientists noted, because bacteria types and activities are variable and the amount of sunlight that reaches the carbon sources can differ by body of water.

In virtually all of the freshwater systems they measured, however, sunlight was always faster than bacteria at converting the organic carbon into CO2.

“This is because most of the fresh water in the Arctic is shallow, meaning sunlight can reach the bottom of any river – and most lakes – so that no dissolved organic carbon is kept in the dark,” said Crump, an associate professor in Oregon State’s College of Earth, Ocean, and Atmospheric Sciences. “Also, there is little shading of rivers and lakes in the Arctic because there are no trees.”

Another factor limiting the microbial contribution is that bacteria grow more slowly in these cold, nutrient-rich waters.

“Light, therefore, can have a tremendous effect on organic matter,” University of Michigan’s Cory pointed out.

The source of all of this organic carbon is primarily tundra plants – and it has been building up for hundreds of thousands of years, but doesn’t completely break down immediately because of the Arctic’s cold temperatures. Once the plant material gets deep enough into the soil, the degradation stops and it becomes preserved, much like peat.

“The level of thawing only gets to be a foot deep or so, even in the summer,” Crump said. “Right now, the thaw begins not long before the summer solstice. If the seasons begin to shift with climate change – and the thaw begins earlier, exposing the organic carbon from permafrost to more sunlight – it could potentially trigger the release of more CO2.”

The science community has not yet been able to accurately calculate how much organic carbon from the permafrost is being converted into CO2, and thus it will be difficult to monitor potential changes because of climate change, they acknowledge.

“We have to assume that as more material thaws and enters Arctic lakes and rivers, more will be converted to CO2,” Crump said. “The challenge is how to quantify that.”

Some of the data for the study was made available through the National Science Foundation’s Arctic Long-Term Ecological Research project, which has operated in the Arctic for nearly 30 years.

Other authors on the study are Collin Ward and George Kling of the University of Michigan.

Media Contact: 
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Byron Crump, 541-737-4369; bcrump@coas.oregonstate.edu;

Rose Cory, 734-615-3199, rmcory@umich.edu

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Byron Crump, OSU

 

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Rose Cory, Michigan

OSU research helps Chinese crested terns make comeback

CORVALLIS, Ore. – A collaborative project between researchers in Oregon and Asia last year helped establish a new breeding colony for one of the world’s most endangered seabirds – the Chinese crested tern – which then had a global population estimated at fewer than 50 birds.

This summer, at least 43 of the critically endangered birds arrived at the colony on the island of Tiedun Dao in Zhejiang Province, forming at least 20 breeding pairs. By early August, 13 young birds had fledged.

“It is a remarkable success story,” said Dan Roby, a professor of wildlife ecology at Oregon State University, who helped establish the new breeding colony. “The lessons that we learned in Oregon through luring Caspian terns to new breeding colonies away from the Columbia River translated quite well to the Chinese crested terns.”

Once thought to be extinct, there were no recorded sightings of Chinese crested terns from the 1930s until 2000, when a few birds were rediscovered on the Matsu Islands. Until last year, there were only two known breeding colonies for this species of tern – both in island archipelagos close to China’s southeast coast.

Both of these colonies have been susceptible to illegal egg collection for food, as well as to typhoons that can devastate seabird breeding colonies, Roby pointed out. The effort to establish a new colony was the first step toward creating a network of island sanctuaries where Chinese crested terns and other seabird species of conservation concern could raise their young, he added.

To establish a new colony, a project team including students and faculty from OSU’s Department of Fisheries and Wildlife worked with colleagues in China to clear part of Tiedun Dao of brush, then planted 300 tern decoys on the island and used solar-powered recorders to broadcast vocalizations of both Chinese crested terns and greater crested terns, which are more numerous and not endangered.

“When greater crested terns establish a breeding colony, sometimes it lures in Chinese crested terns as well,” Roby said. “We just didn’t expect it to happen so quickly.”

The China project was designed to recapture the success that Roby and the Army Corps of Engineers had in establishing new breeding colonies in Oregon for Caspian terns far away from the Columbia River, where they had been decimating juvenile salmon migrating downstream. They established new colonies in southeast Oregon and successfully lured thousands of birds to the new sites.

The technique of clearing vegetation, planting decoys and luring birds through playback of vocalizations was developed by Stephen Kress of the National Audubon Society.

Even though the new breeding colony for Chinese crested terns was successful, it wasn’t without peril, according to Simba Chan, senior conservation officer of BirdLife International’s Asia Division, who stayed on Tiedun Dao from early May to early August to monitor the colony. During that time, the endangered birds and their chicks endured attempted predation by peregrine falcons, attempted poaching by an egg collector, and three typhoons.

Chan and his colleagues collected a lot of data about the birds’ behavior that will help inform the management of the birds as well as the design of future colonies.

Chinese crested terns are highly efficient at finding and catching forage fish and adept at defending their nest sites during territorial disputes with their neighbors. Crested terns breed in very dense colonies with six to seven nesting pairs per square meter. The decline and near-extinction of Chinese crested terns in the 20th century was likely due to their restricted breeding range and widespread overharvest of seabird eggs.

“Having a new, productive breeding site away from the other two known colonies gives the species a far better chance to recover,” Roby said.

The project was supported by numerous international groups.

Media Contact: 
Source: 

Dan Roby, 541-737-1955; Daniel.roby@oregonstate.edu

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