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New maps may reduce tourism impacts on Hawaiian dolphins

Location of the study site in the Hawaiian Archipelago

Over-eager eco-tourists intent on seeing spinner dolphins up close may inadvertently be disturbing the charismatic animals' daytime rest periods and driving them out of safe habitats in bays along Hawaii's coast.

Scientists at Duke and Stony Brook universities have developed a promising new tool that may help to limit repeated human disturbances and help reduce their negative impacts on the dolphins.

"Using the maps produced through this study we can identify the bays where the effects of human activities on spinner dolphins should be monitored most closely, and where immediate conservation actions are required," said David W. Johnston, research scientist at Duke's Nicholas School of the Environment.

The researchers' tool shows that only a small number of bays – 21 out of 99 – in a study area along the western coastlines of the main Hawaiian islands were suitable habitats for resting dolphins. Knowing this, "conservation efforts can be focused on specific areas of importance," Johnston said,

"We may be able to minimize detrimental effects on dolphins by putting restrictions or preventative measures into place in a relatively small number of bays, rather than limiting access to dolphins along the entire coast," said the study's lead author, Lesley H. Thorne, a lecturer in marine science at Stony Brook University, who received her PhD from Duke in 2010. "That benefits tourists and tourism operators as well as the dolphins."

In the study, the researchers used the geographic coordinates and key environmental factors – such as water depth and calmness, the size and proportions of the bays and distances from deep-water foraging grounds – for hundreds of spinner dolphin sightings made in the study area between 2000 and 2010. The results appear August 27 in the online, open-access peer-reviewed journal PLoS ONE. 

Spinners are small dolphins famed for their graceful aerial movements and balletic spins. They are found in tropical and subtropical oceans around the world and some divide their time between daytime rest periods in shallow, protected bays and nighttime foraging in more exposed waters.

Distinguishing between sightings of resting and active dolphins was key to defining critical habitats, Thorne said. While socially active spinner dolphins are more tolerant of humans' presence, resting dolphins will leave the safety of a bay and retreat to less suitable open waters if humans repeatedly disturb them.

"Sleep is essential for most animals," added Johnston. "When deprived of their necessary 'zzzz's,' they gradually show a decreased ability to process information and remain attentive to environmental stimuli. In technical lingo, we call this a 'vigilance decrement'."

Spinner dolphins are no exception to the rule. The researchers say dolphins that experience human harassment every day during their rest periods never fully recover their vigilance decrement. Their ability to forage successfully and detect the presence of nearby predators is also degraded, and their ability to produce sounds to communicate and navigate may also be impaired, he said.

Scientists and conservationists have long worried that spinners' popularity with tourists – and overlap of their resting habitats with popular ocean recreation destinations – may be placing them at risk. Reports of interactions have increased sharply in recent years, but few published studies have examined the detrimental impacts these interruptions may have on the animals, especially at the population level.

"It would be next to impossible to survey spinner populations and human activities in every bay that might be a resting habitat," Thorne said. "We're talking about hundreds of bays in the Hawaiian islands alone."

"Using predictive models, such as the maximum entropy spatial modeling approaches we've produced, is a much more cost-effective method," she said. "This type of modeling has only recently been applied to the study of marine mammals, but our study suggests it may be especially useful."

Thorne and Johnston plan to test their models by conducting similar studies of spinner dolphin distributions and habitat use in the Northwestern Hawaiian Islands and other sites in the Pacific islands region. Results from those studies, they said, could confirm the new models' usefulness.

Johnston and Thorne's co-authors on the PLoS ONE study include Dean L. Urban, professor of landscape ecology at Duke's Nicholas School, and Lars Bejdar, associate professor at Murdoch University, Australia, and adjunct assistant professor at Duke.

The data on spinner dolphin sightings used to develop the models in the study were provided by a team of eight additional co-authors from Murdoch University, the Pacific Islands Photo-Identification Network, the Cascadia Research Collective, the Hawai'i Marine Mammal Consortium, the Hawai'i Association for Marine Education and Research, the Dolphin Institute, the University of Hawai'i (UH) at Hilo, UH at Mānoa, and Marine Mammal Research Consultants.

Reference: "Predictive modeling of spinner dolphin (Stenella longirostris) resting habitat in the main Hawaiian Islands," L.H. Thorne, D.W. Johnston, D.L. Urban, J. Tyne, L. Bejder, R.W. Baird, S. Yin, S.H. Rickards, M.H. Beakos, J.R. Mobely Jr., A.A. Pack, M.C. Hill. PLoS ONE, August 24, 2012. DOI: 10.1371/journal.pone.0043167

Contact: Tim Lucas
tdlucas@duke.edu
919-613-8084
Duke University

 

 

George Washington University Computational Biology Director solves 200-year-old oceanic mystery

Keith Crandall finds the connection between 'monster larva' and unique species of shrimp

Plesiopenaeus armatus

The origin of Cerataspis monstrosa has been a mystery as deep as the ocean waters it hails from for more than 180 years. For nearly two centuries, researchers have tried to track down the larva that has shown up in the guts of other fish over time but found no adult counterpart. Until now.

George Washington University Biology Professor Keith Crandall cracked the code to the elusive crustacean's DNA this summer. His findings were recently published in the journal "Ecology and Evolution," and his research was funded by the National Science Foundation and the Gulf of Mexico Research Initiative. In it, Dr. Crandall, the senior author of the paper, explains how "monster larva" and the deep-water aristeid shrimp known as Plesiopenaeus armatus are one in the same: larvae and adult forms of the same species.

Attempts to find the adult incarnation of the larva weren't without significant effort over the span of time. The crustacean's ability to morph into a shrimp bearing no resemblance to its juvenile form was a challenge as externally, the two couldn't be more different.

C. monstrosa, has heavy armor, a thick body and exceptional horn ornamentation. Described as "monstrous and misshapen animal," it is the preferred meal for its predators such as skipjack, yellowfin and blackfin tuna and dolphin. The Plesiopenaeus, resembles a lobster or crab with its red, enclosed exterior and is elusive. It calls the deep sea waters such as the Atlantic Ocean home but finding the specimen to make a match has proven to be difficult for zoologists.

Dr. Crandall said it was not until the late 19th century that researchers started to suspect a link between the Cerataspis and some of the deep sea shrimp. Mid-water oceanic collections in the northern Gulf of Mexico unexpectedly included a single specimen of C. monstrosa for genetic analyses.

"Because previous studies suggested an affinity between Cerataspis and penaeoid shrimp, and more specifically the family Aristeidae, we sampled heavily within these groups," he said. The Crandall lab has been collecting crustacean DNA sequence data for a number of years and therefore had an excellent reference database to compare the Cerataspis DNA.

That's when analysis placed the larva and the deep-sea shrimp as one in the same.

"It's very exciting to have solved a nearly 200-year-old conundrum," said Dr. Crandall. "This was a project that involved having good luck with obtaining the sample, exceptional field knowledge to preserve the specimen and know that it was something special, outstanding state-of-the-art molecular and analytical tools to collect unique data that have only been available in the last 10 years to answer this question and to have an outstanding database of reference sequences to compare against."

The National Oceanic and Atmospheric Administration also supported some of the research by providing financial support for the ship time, ship, crew members and collection resources.

"Larval-adult linkages not only aid in our understanding of biodiversity, they provide insights into the life history, distribution and ecology of an organism," said Dr. Crandall.

Dr. Crandall, a renowned biologist and population geneticist, was named founding director of the George Washington University Computational Biology Institute in June. His responsibilities include defining the scientific vision of the institute and directing the development and implementation of research plans and organizational structures.

In the heart of the nation's capital with additional programs in Virginia, the George Washington University was created by an Act of Congress in 1821. Today, GW is the largest institution of higher education in the District of Columbia. The university offers comprehensive programs of undergraduate and graduate liberal arts study, as well as degree programs in medicine, public health, law, engineering, education, business and international affairs. Each year, GW enrolls a diverse population of undergraduate, graduate and professional students from all 50 states, the District of Columbia, and more than 130 countries.

Contact: Latarsha
lgatlin@gwu.edu
202-994-5631
George Washington University

 

 

Darwin discovered to be right: Eastern Pacific barrier is virtually impassable by coral species

		A coral species that is found in abundance from Indonesia eastward to Fiji, Samoa, and the Line Islands rarely crosses the Eastern Pacific Barrier toward the coast of the Americas, according to a team of researchers led by Iliana Baums, an assistant professor of biology at Penn State University. The research, which will be published in the journal Molecular Ecology, has important implications for climate-change research, species-preservation efforts, and the economic stability of the eastern Pacific region, including the Galapagos, Costa Rica, Panama, and Ecuador. This photo shows Dr. Iliana Baums collecting coral samples in the Pacific Ocean. Credit: Joshua Feingold, Nova Southwestern University

A coral species that is found in abundance from Indonesia eastward to Fiji, Samoa, and the Line Islands rarely crosses the Eastern Pacific Barrier toward the coast of the Americas, according to a team of researchers led by Iliana Baums, an assistant professor of biology at Penn State University. Darwin hypothesized in 1880 that most species could not disperse across the marine barrier, and Baums's study is the first comprehensive test of that hypothesis using coral. The results of the scientific paper, which will be published in the journal Molecular Ecology, has important implications for climate-change research, species-preservation efforts, and the economic stability of the eastern Pacific region, including the Galapagos, Costa Rica, Panama, and Ecuador.

The Eastern Pacific Barrier (EPB) -- an uninterrupted 4,000-mile stretch of water with depths of up to 7 miles -- separates the central from the eastern Pacific Ocean. In his writings, Darwin had termed this barrier "impassable" and, since Darwin's time, scientists have confirmed that many species of marine animals cannot cross this oceanic divide. However, until now, researchers had not performed a comprehensive analysis of the impact of the barrier on coral species. "The adult colonies reproduce by making small coral larvae that stay in the water column for some time, where currents can take them to far-away places," Baums said. "But the EPB is a formidable barrier because the time it would take to cross it probably exceeds the life span of a larva."

A map of the Pacific Ocean showing where coral samples were collected. Circles of the same color indicate corals that are genetically similar. Clipperton Island has corals that are genetically similar to those found throughout the central Pacific, suggesting that larvae from the central Pacific traveled eastward to populate Clipperton. Blue arrows indicate cool ocean currents; red arrows indicate warm ocean currents. The inset image shows the study species, Porites lobata. Credit: Baums lab, Penn State University

To test whether or not coral larvae are able to travel across the barrier, Baums and her team chose a particularly hearty species called Porites lobata. "Compared with other coral species, Porites lobata larvae seem able to survive for longer periods of time; for example, the weeks that are required to travel across the marine barrier," Baums said. "This species also harbors symbionts in its larvae that can provide food during the long journey. In addition, the adults seem able to brave more extreme temperatures, as well as more acidic conditions. So, if any coral species is going to make it across, it is this one."

Baums and her team hypothesized that coral larvae originating in the central Pacific might be pushed along the North Equatorial Counter Current, which flows from west to east and becomes stronger and warmer in years with an El Niño Southern Oscillation event -- a climate pattern that occurs about every five years. "Coral larvae are not very mobile," Baums said. "So the only way coral larvae originating to the west of the barrier could travel to the east is along an ocean current, and warming of a current like the North Equatorial Counter Current would help larvae survive. If coral have traveled along this current in the past, we should find populations that are genetically similar living from the Galapagos to Costa Rica, Panama, and Ecuador."

The team members collected coral samples of the Porites lobata species from both sides of the Eastern Pacific Barrier and performed genetic tests using special markers called microsatellites -- repeating sequences of DNA that are informative for the purpose of distinguishing among individuals. "We found that Darwin was right: the EPB is a very effective barrier," Baums said. "For the most part, samples we found to the east are genetically dissimilar to those we found to the west. This means that coral larvae originating in the central Pacific simply are not making it across the ocean to the Americas."

The only exception, the team found, was a relatively small population of Porites lobata living near Clipperton Island, which is located just north and west of the Galapagos. The samples collected there were genetically similar to samples found throughout the central Pacific, indicating that the species had migrated there from the west relatively recently. "Interestingly, the coral that are lucky enough to cross the EPB to Clipperton Island stay there and don't go any farther," Baums explained. "In other words, we find that Porites lobata are not migrating south and east to the Galapagos after making it to Clipperton. We believe this is because these coral are adapted to the warmer conditions that their parents enjoyed to the west of the EPB; for example, near the Line Islands, Fiji, and Samoa. "Coral reefs thrive in shallow water in areas where the annual mean temperature is about 64 degrees Fahrenheit," Baums said. "The eastern Pacific tends to be much cooler; in part, because of a process called upwelling -- a phenomenon that occurs when winds stir up cold, deep ocean water, pulling it to the surface. Clipperton Island may provide a similar-enough environment to the Central Pacific, but the Galapagos area simply may be too cool."

The team's findings about the ability of coral to travel across the marine barrier have important implications for the economic stability of the eastern Pacific, the region's species-conservation efforts and, more broadly, for the impact of climate change on tropical ecosystems. The Galapagos, Costa Rica, Panama, and Ecuador all rely heavily on tourism. Tourism, in turn, relies on healthy reefs that divers can visit and the sale of shellfish and lobster -- species that are maintained, in large part, by the presence of coral communities.

"The take-home message is that coral populations in the eastern Pacific need to be protected," Baums said. "That is, in the event of any large-scale coral crisis, we cannot count on coral populations in the eastern Pacific being replenished by larvae from the west." Baums explained that, especially as the Earth's surface continues to warm, such a crisis to coral reefs is not unlikely. During the El Niño Southern Oscillation events that occurred from 1982 to 1983 and from 1997 to 1998, some of the reefs experienced a 90-percent loss. Although they ultimately were able to bounce back, a stronger El Niño event might spell extinction for some coral species.

In addition to Baums, other researchers who contributed to the study include Jennifer Boulay and Nicholas R. Polato at Penn State and Michael E. Hellberg at the Louisiana State University.

The research was funded by the National Science Foundation.

Contact: Barbara Kennedy
science@psu.edu
814-863-4682
Penn State

 

 

Arctic sea ice reaches lowest extent ever recorded, says CU-Boulder research team

		The extent of Arctic sea ice reached a record low in the satellite record on Aug. 26 and is expected to continue dropping for the next several weeks, according to a University of Colorado Boulder research team. Credit: NSIDC, University of Colorado Boulder

The blanket of sea ice floating on the Arctic Ocean melted to its lowest extent ever recorded since satellites began measuring it in 1979, according to the University of Colorado Boulder's National Snow and Ice Data Center.

On Aug. 26, the Arctic sea ice extent fell to 1.58 million square miles, or 4.10 million square kilometers. The number is 27,000 square miles, or 70,000 square kilometers below the record low daily sea ice extent set Sept. 18, 2007. Since the summer Arctic sea ice minimum normally does not occur until the melt season ends in mid- to-late September, the CU-Boulder research team expects the sea ice extent to continue to dwindle for the next two or three weeks, said Walt Meier, an NSID scientist.

"It's a little surprising to see the 2012 Arctic sea ice extent in August dip below the record low 2007 sea ice extent in September," he said. "It's likely we are going to surpass the record decline by a fair amount this year by the time all is said and done."

On Sept. 18, 2007, the September minimum extent of Arctic sea ice shattered all satellite records, reaching a five-day running average of 1.61 million square miles, or 4.17 million square kilometers. Compared to the long-term minimum average from 1979 to 2000, the 2007 minimum extent was lower by about a million square miles -- an area about the same as Alaska and Texas combined, or 10 United Kingdoms.

While a large Arctic storm in early August appears to have helped to break up some of the 2012 sea ice and helped it to melt more quickly, the decline seen in in recent years is well outside the range of natural climate variability, said Meier. Most scientists believe the shrinking Arctic sea ice is tied to warming temperatures caused by an increase in human-produced greenhouse gases pumped into Earth's atmosphere.

CU-Boulder researchers say the old, thick multi-year ice that used to dominate the Arctic region has been replaced by young, thin ice that has survived only one or two melt seasons -- ice which now makes up about 80 percent of the ice cover. Since 1979, the September Arctic sea ice extent has declined by 12 percent per decade.

The record-breaking Arctic sea ice extent in 2012 moves the 2011 sea ice extent minimum from the second to the third lowest spot on record, behind 2007. Meier and his CU-Boulder colleagues say they believe the Arctic may be ice-free in the summers within the next several decades.

"The years from 2007 to 2012 are the six lowest years in terms of Arctic sea ice extent in the satellite record," said Meier. "In the big picture, 2012 is just another year in the sequence of declining sea ice. We have been seeing a trend toward decreasing minimum Arctic sea ice extents for the past 34 years, and there's no reason to believe this trend will change."

The Arctic sea ice extent as measured by scientists is the total area of all Arctic regions where ice covers at least 15 percent of the ocean surface, said Meier.

Scientists say Arctic sea ice is important because it keeps the polar region cold and helps moderate global climate -- some have dubbed it "Earth's air conditioner." While the bright surface of Arctic sea ice reflects up to 80 percent of the sunlight back to space, the increasing amounts of open ocean there -- which absorb about 90 percent of the sunlight striking the Arctic -- have created a positive feedback effect, causing the ocean to heat up and contribute to increased sea ice melt.

Earlier this year, a national research team led by CU embarked on a two-year effort to better understand the impacts of environmental factors associated with the continuing decline of sea ice in the Arctic Ocean. The $3 million, NASA-funded project led by Research Professor James Maslanik of aerospace engineering sciences includes tools ranging from unmanned aircraft and satellites to ocean buoys in order to understand the characteristics and changes in Arctic sea ice, including the Beaufort Sea and Canada Basin that are experiencing record warming and decreased sea ice extent.

NSIDC is part of CU-Boulder's Cooperative Institute for Research in Environmental Sciences -- a joint institute of CU-Boulder and the National Oceanic and Atmospheric Administration headquartered on the CU campus -- and is funded primarily by NASA.

NSIDC's sea ice data come from the Special Sensor Microwave Imager/Sounder sensor on the Defense Meteorological Satellite Program F17 satellite using methods developed at NASA's Goddard Space Flight Center in Greenbelt, Md.

Contact: Natasha Vizcarra
natasha.vizcarra@nsidc.org
303-492-1497
University of Colorado at Boulder

 

 

MBL scientists discover nerves control iridescence in squid’s remarkable 'electric skin'

		Nerves in red can be easily traced among the distinctive chromatophores and iridophores that they innervate. Credit: Wardill, Gonzalez-Bellido, Crook & Hanlon, Proceedings of the Royal Society B: Biological Sciences

Squid's colorful, changeable skin enables the animal--and their close relatives, cuttlefish and octopus--to display extraordinary camouflage, the speed and diversity of which is unmatched in the animal kingdom.

But how squid control their skin's iridescence, or light-reflecting property, which is responsible for the animal's sparkly rainbow of color, has been unknown.

In a new study, MBL (Marine Biological Laboratory) researchers Paloma Gonzalez Bellido and Trevor Wardill and their colleagues report that nerves in squid skin control the animal's spectrum of shimmering hues--from red to blue--as well as their speed of change. The work marks the first time neural control of iridescence in an invertebrate species has been demonstrated.

		Neurally activated iridescence in squid iridophores. Doryteuthis pealeii have conspicuous pigmentary chromatophores and underlying structurally colored iridophores. Credit: Wardill, Gonzalez-Bellido, Crook & Hanlon, Proceedings of the Royal Society B: Biological Sciences

Squid skin is extraordinary because it has two ways to produce color and pattern. Pigmented organs called chromatophores create patterns with yellow, red, and brown colors. Underneath the pigments, iridophores, aggregations of iridescent cells in the skin, reflect light and add blue, green, and pink colors to the overall appearance of the skin. Collectively these two groups of skin elements can create spectacular optical illusions with patterns of color, brightness, and contrast change.

"For 20 years we have been wondering how the dynamically changeable iridescence is controlled by the squid," says study co-author Roger Hanlon. "At long last we have clean evidence that there are dedicated nerve fibers that turn on and tune the color and brightness of iridophores. It is not an exaggeration to call this "electric skin." The complex nerve network distributed throughout the squid's skin instantly coordinates tens of thousands of chromatophores with iridescent reflectors for rapidly changing behaviors ranging from camouflage to signaling."

		Yellow, red, and brown chromatophores (organs composed of a large pigment cell) surround a single iridophore, which consists of hundreds of iridescence cells. A nerve bundle (not in view of video) is electrically stimulated when the red square appears in upper left corner. Brief electrical pulses initiate action potentials in the nerves which travel to the iridophores and chromatophores. At first the chromatophores respond, but with time, the iridophores also respond. The movie is 4 times normal speed. Credit: Wardill, Gonzalez-Bellido, Crook & Hanlon, Proceedings of the Royal Society B: Biological Sciences

Working with longfin inshore squid (Doryteuthis pealeii), the researchers took a new approach to investigating the mystery behind the iridophore control mechanism. By tracing a highly branched network of nerves and stimulating them electrically, they found that they could activate progressive color shifts from red and orange to yellow, green, and blue in just 15 seconds. The findings suggest that the specific color of each iridophore, as well as speed of change, is controlled by the nervous system, as is spatial chromatophore patterning that occurs in the skin layer just above.

How squid choose and hold particular skin colors to help camouflage themselves remains unknown and is particularly interesting because the animals are completely colorblind.

"One possibility is the animals do not care about the color of the iridophores, but shifting the color from red to blue will dramatically increase the relative brightness of iridophores," says Wardill. "This is because squid see predominantly blue light. Blue light is especially important in the ocean as it penetrates best into deeper water."

The study, co-authored by Gonzalez Bellido, Wardill, Hanlon of the MBL and Robyn Crook of University of Texas Medical School at Houston appeared in the August 15th issue of the journal Biological Sciences. The work was funded by grants from the Office of Naval Research (ONR), Defense Advanced Research Projects Agency (DARPA), and Air Force Office of Scientific Research.

The Marine Biological Laboratory (MBL) is dedicated to scientific discovery and improving the human condition through research and education in biology, biomedicine, and environmental science. Founded in 1888 in Woods Hole, Massachusetts, the MBL is an independent, nonprofit corporation.

Contact: Gina Hebert
ghebert@mbl.edu
508-289-7725
Marine Biological Laboratory

 

 

How ocean currents affect global climate is a question oceanographer may be close to answering

A new way of thinking about ocean currents: Kevin Speer looks to the Southern Ocean for answers

		This video is titled "A New Way of Thinking About Ocean Currents. "

Kevin Speer has a "new paradigm" for describing how the world's oceans circulate — and with it he may help reshape science's understanding of the processes by which wind, water, sunlight and other factors interact and influence the planet's climate.

A Florida State University professor of oceanography with a passion for teaching, Speer and a colleague recently published a significant paper in the respected journal Nature Geoscience.

Working with John Marshall, an oceanography professor at the Massachusetts Institute of Technology, Speer reviewed — or essentially synthesized — vast amounts of previous data on ocean circulation (including their own earlier papers). As a result, they have created what Speer calls a new paradigm in the study of ocean currents on a global scale.

Here's how it works: Basically, the oceans, together with the atmosphere, rebalance heat on the planet. The sun shines on the Earth and heats up the tropics more than the poles. Near the poles, the ocean is cold and the water sinks; near the equator, the surface of the ocean is inviting and warm — and floats on top of the colder deep water.

So the question is this: Where does the water that goes down come back up?

Speer, Marshall and other oceanographers now believe that it comes back up in the Southern Ocean surrounding Antarctica — not as much in the warm oceans as had been previously thought.

"We're not saying that nothing comes up in the rest of the World Ocean, just that the main thrust is in the Southern Ocean," Speer said. "To a large extent it's driven by the wind."

Very strong winds, to be precise.

		Speer and his students have been studying ocean currents thanks to $2.5 million in funding from a larger $10 million National Science Foundation grant that FSU shares with eight other universities and institutions worldwide. Credit: Bill Lax/FSU Photographic Services

In the rough waters around Antarctica, sailors call those winds the "Roaring Forties" and the "Furious Fifties." They originate near the Equator, where hot air rises and then is pushed toward the North and South poles by cooler air that rushes in to take its place.

The resulting "eddy-driven upwelling" in the Southern Ocean, as Speer characterizes it, may in fact describe the most important process to date that helps scientists understand the role of the ocean and climate.

Speer, who holds a doctorate in physical oceanography from the prestigious Massachusetts Institute of Technology/Woods Hole Oceanographic Institution Joint Program, spent years living in France as an oceanographic researcher for a French governmental agency. (Yes, he's fluent in French.)

		Kevin Speer is a professor of physical oceanography at Florida State University. Credit: Bill Lax/FSU Photographic Services

Today, from his office on the Florida State campus, Speer serves as interim director of the Geophysical Fluid Dynamics Institute, a warren of intriguing laboratories just a few steps outside his door. It is there that Speer helps students and postdoctoral researchers learn about how climate works.

The laboratory's equipment includes a large, vintage rotating table designed nearly a half-century ago by the lab's founder, Florida State meteorology Professor Richard Pfeffer. (The device may be old, but it's one of the biggest and best in the United States, Speer says). Here students can recreate the ocean's churning and study natural phenomena such as the Antarctic circumpolar current.

Speer and his students have been studying ocean currents thanks to $2.5 million in funding from a larger $10 million National Science Foundation grant that FSU shares with eight other universities and institutions worldwide. Research has included releasing tracers and floats into the ocean to study the mixing and spreading of currents.

One of Speer's graduate students, Druv Balwada, recently took part in a joint U.S.-United Kingdom research program to study ocean currents aboard a ship in the Southern Ocean. To view the cruise blog of the nearly three-month voyage, visit this website.

"Our students learn and help in various ways," Speer said. "They certainly help generate some interesting and lively oceanographic research."

Reference: Speer and Marshall's Nature Geoscience paper is titled "Closure of the Meridional Overturning Circulation Through Southern Ocean Upwelling".

Contact: Kevin Speer
kspeer@fsu.edu
850-644-5594
Florida State University

 

 

How methane becomes fish food

Västmanland, Sweden. Credit: Olof Senestam

Methane is an organic carbon compound containing the fundamental building block of nearly all living material: carbon. It provides an important source of energy and nutrients for bacteria. Methane is produced in oxygen-free environments and is found in abundance at the bottom of lakes.

The Brazilian post-doctoral researcher in biology and ecology, Angela Sanseverino, has presented a study that shows methane from lakebeds to be present in fish tissue. The study was carried out in cooperation with, inter alia, David Bastviken, Water and Environmental Studies (WES), Linköping University.

Angela Sanseverino has studied a combination of two biomarkers: a stable isotope that indicates the presence of methane along with a specific fatty acid from methane-oxidizing bacteria. The study was carried out on fish and other parts of the food web from a lake in the Pantanal, inland Brazil. The findings of the study have been reported in a recently published article in the prestigious online research journal PLOS ONE.

"This is the first time we can say with any great certainty that methane from the lake bed has ended up in fish tissue via the food chain", says David Bastviken. "Isotopic studies have been carried out in the past, but they have been more uncertain as they only related to one biomarker. We now have two independent biomarkers presenting the same results. This considerably increases the certainty of our findings."

"It is like opening a black box. It turns out that carbon, which we thought was lost forever, can return to the food chain."

Methane is taken up by methane oxidizing bacteria, which in turn are eaten by zooplankton and other aquatic organisms. These organisms eventually end up in fish stomachs, meaning that food webs not only feed off organic carbon from plants in the lake or from the surrounding land; but also from deep-lying and oxygen-free, yet carbon-rich, sediment stores where methane is formed.

More studies are being planned to show the potentially vast importance that methane could have on the food chain in different types of lakes and conditions. For example, what happens in Swedish lakes during the winter?

However, David Bastviken,  Associate professor (Lektor), Detpt. of Thematic Studies - Water and Environemntal Studies, Linköping University, does not believe these studies will affect his estimates of the methane emissions from lakes and watercourses. He has previously proven that these have most likely been greatly underestimated in the existing calculations of the global greenhouse gas emissions.

Reference: Methane Carbon Supports Aquatic Food Webs to the Fish Level by Sanseverino AM, Bastviken D, Sundh I, Pickova J, Enrich-Prast A (2012). PLoS ONE 7(8)

Contact: David Bastviken
david.bastviken@liu.se
46-132-82291
Linköping University