Research Highlights
News & Insights
WHOI geochemist Chris German pairs an autonomous surface vehicle (ASV) called a Wave Glider with other vehicles to expand research here and on other Ocean Worlds
Researchers investigate dust from the ocean’s farthest point from land to reconstruct the climactic history of the Southern Hemisphere, and understand how micronutrients have influenced biological productivity in this oceanic desert.
WHOI-MIT joint program student outfits her basement to do vital work on a marine carbon sensor
Infographics strive to give us a sense of how long plastic goods will last in the environment. But is this information reliable? The findings of a new study from WHOI may surprise you.
Marine life has been naturally producing toxic chemicals well before chemical companies were manufacturing PCBs. But are these naturally-produced compounds as harmful as man-made environmental pollutants, and do those pose a human health threat?
A marine chemist spends his time at home tinkering on a high-tech buoy in the basement, proving that being homebound doesn’t mean you can’t think big.
Ken Buesseler joins the hosts of Future Hindsight Podcast to talk about the safety of the Pacific Ocean, the natural occurrence of radioactivity in our environment, and a citizen scientist project for oceanic testing.
A decade of research since the Deepwater Horizon disaster has revealed how sunlight—its importance long understated in oil spill science—substantially alters petroleum floating at the sea surface.
The test being used to diagnose the novel coronavirus—and other pandemics like AIDS and SARS—was developed with the help of an enzyme isolated from a microbe found in marine hydrothermal vents as well as freshwater hot springs.
News Releases
A study published Aug. 28, 2017, in the Proceedings of the National Academy of Sciences adds a new dimension to the controversial decision to inject large amounts of chemical dispersants immediately above the crippled oil well at the seafloor during the Deepwater Horizon disaster in 2010. The dispersants likely reduced the amount of harmful gases in the air at the sea surface—diminishing health risks for emergency responders and allowing them to keep working to stop the uncontrolled spill and clean up the spilled oil sooner.
In the midst of the Deepwater Horizon crisis, officials made the unprecedented and controversial decision to inject more than 700,000 gallons of chemical dispersant over 67 days immediately above the oil rig’s severed wellhead at the bottom of the ocean. The objective was to break up petroleum that surged uncontrollably from the wellhead into smaller droplets in the deep sea, with the goals of diminishing oil slicks and reducing the amount of harmful gases arriving at the ocean surface.
Proponents said the dispersants did help dissipate oil slicks on the sea surface, causing less oil to taint shoreline beaches and marshes. Opponents said the dispersants themselves were toxic, may have caused environmental damage, and were not effective at reducing the already small droplets forming at the wellhead.
To this debate, the new study demonstrates a beneficial effect of dispersants: The subsea dispersant injection likely allowed emergency responders literally to breathe easier. By breaking up petroleum into smaller droplets that dissolved faster in the deep ocean, the dispersants decreased the amounts of volatile toxic compounds that rose to the surface and outgassed into the air. That dramatically improved the air quality for responders and presumably reduced the number of days when the air quality was too poor and responders had to don respirators and/or had to suspend cleanup efforts.
The research team included: Jonas Gros, Scott Socolofsky, Anusha Dissanayake, and Inok Jun (Texas A&M University); Lin Zhao and Michel Boufadel (New Jersey Institute of Technology); Christopher Reddy (Woods Hole Oceanographic Institution); and J. Samuel Arey (Swiss Federal Institute of Aquatic Science and Technology). The research was funded by the Gulf of Mexico Research Initiative and the National Science Foundation.
Dispersants have been applied to oil slicks on the ocean surface for half a century to break petroleum into smaller droplets that dissipate into waters of the open ocean so that less oil reaches ecologically sensitive coastlines. But, they had never been used at the unprecedented depth of 5,000 feet beneath the surface, where an estimated 7,500 tons per day of oil and 2,400 tons per day of natural gas were jetting from the ruptured wellhead near the seafloor. This flow rate is equivalent to 57,000 barrels per day of oil and 92 million cubic feet per day of gas being produced at standard conditions at the sea surface. During the period studied by the authors, 19,000 barrels per day of oil were also captured by an inverted funnel, or “top hat,” that was placed directly above the wellhead, which decreased the amount of oil that escaped into the sea.
“U.S. government and industry responders had to make a crucial decision. They were facing an enormous oil spill, gushing uncontrollably from a wellhead at the seafloor—at a depth where no oil spill had ever happened before,” Reddy and Arey wrote in an article in Oceanus magazine. “They were pitted in a high-stakes battle against big unknowns.”
Officials made a crucial decision to proceed with the subsurface injection of Corexit EC9500A, a dispersant that roughly resembles a mix of food-grade mineral oil, windshield-wiper fluid, and household dish detergent.
Aerial photographs and anecdotal accounts suggested that the deep-sea dispersant injection may have helped dissipate the oil slicks at the surface and improve air quality around responder boats working near the disaster site. But in the heat of the crisis, officials did not take the time to design and implement robust experiments to measure the detailed effects of the injection.
In the new study, scientists built and tested a mathematical model that simulated the complex chemical and physical interactions among water, oil, gas, and dispersant that occurred during Deepwater Horizon. They focused on the period starting June 3, 2010, when the riser pipe was cut at the wellhead by engineers, until July 15, 2010—a timespan when a large number of scientific observations were collected nearby in the air and ocean. To test the model’s ability to simulate the real-world disaster, they compared the model predictions to the observations. Nearly all those comparisons aligned with the model’s output, indicating that the model replicated many aspects of what happened to oil and gas under the ocean surface.
The research team then used the model to conduct a key test that was never done in real life: They ran the model to see what likely would have happened if dispersants had not been injected immediately above the wellhead during the same time period.
The model results indicated that deep-sea dispersant injection had a profound effect on air quality at the ocean surface. The injection of the subsea dispersant caused the turbulent jet of petroleum fluids to form oil droplets that were about 30 times smaller (by volume) than they would have been without dispersants, according to the model results. This subtle change caused many volatile petroleum chemicals to dissolve more rapidly and become entrapped in the deep sea. According to the study, most of the highly toxic benzene and toluene in the oil were transported away in deep currents, along with other entrapped petroleum compounds that affected organisms on and near the sea floor. The benzene and toluene likely would have become biodegraded within weeks.
“In 2010 when NSF began rapid response funding for research on Deepwater Horizon, it was important to characterize the initial conditions of the spill, such as plume dynamics and ecological effects,” said Don Rice, a program director in the NSF’s Division of Ocean Sciences. “These scientists and others did just that. As the findings of this study clearly demonstrate, the discoveries of basic scientific research and the ensuing practical applications in their wake are often utterly unanticipated.”
The model showed that the dispersant injection decreased the overall concentration of all volatile organic chemicals in the atmosphere by a modest amount (about 30 percent). But it also significantly reduced the amount of chemicals most harmful to humans, such as benzene and toluene. The atmospheric concentration of benzene, for example, decreased by about 6,000 times, dramatically improving air quality.
Without the dispersant injection, the model showed that benzene concentrations in the air 2 meters above the sea surface would have been 13 times higher than the levels considered acceptable to breathe during a 10-hour working day or a 40-hour work week, based on guidelines by the National Institute of Occupational Safety and Health (NIOSH). However, with dispersant injection, the model showed atmospheric benzene concentrations were 500 times lower than the levels considered acceptable to breathe by NIOSH.
“These predictions depend on local weather conditions that can vary from day to day. However, we predict that cleanup delays would have been much more frequent if subsurface dispersant injection had not been applied,” Reddy and Arey say.
“But this one study is not the final say on the usage of dispersants,” they added. “It is another row on a ledger sheet called the ‘spill impact mitigation analysis,’ ” which assesses various strategies and tools to reduce environmental and economic damage caused by oil spills. “All potential positive and negative effects of dispersant injection need to be taken into account before final judgements on their future use can be robustly determined,” they said.
The debate about using dispersants is becoming increasingly politicized and acrimonious, and the National Academy of Sciences has recently assembled a committee of scientists, government officials, and industry to evaluate the use of chemical dispersants in oil spill response.
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The Woods Hole Oceanographic Institution is a private, non-profit organization on Cape Cod, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate a basic understanding of the ocean’s role in the changing global environment. For more information, please visit www.whoi.edu.
When it comes to coral health, superoxide—a natural toxin all oxygen-breathing organisms produce—gets a bad rap.
Scientists have called superoxide out as the main culprit behind coral bleaching: The idea is that as this toxin builds up inside coral cells, the corals fight back by ejecting the tiny energy- and color-producing algae living inside them. In doing so, they lose their vibrancy, turn a sickly white, and are left weak, damaged, and vulnerable to disease.
Now, a new study from the Woods Hole Oceanographic Institution (WHOI) is casting a more positive light on superoxide. It suggests that when these molecules are produced at coral surfaces—outside of their cells—they may actually play a beneficial role in coral health and resilience. The research that results from this finding may contribute to future strategies for preventing corals from bleaching.
“Superoxide has largely been vilified as a stress molecule and implicated as the main cause of coral bleaching,” said Colleen Hansel, a WHOI biogeochemist and lead author of the study published December 7 in the journal Nature Communications. “But when we measured superoxide concentrations at the surface of corals during a natural bleaching event, we saw a completely different dynamic. It appears this ‘toxin’ may have provided a benefit to the corals—perhaps helping some species to resist bleaching.”
Hansel said the researchers were surprised to see that, during the bleaching event, coral species that were more susceptible to bleaching weren’t producing external superoxide, while those that resisted bleaching produced high concentrations.
“While we don’t yet understand how corals produce superoxide externally, this discovery points to a fundamental misunderstanding of what this group of compounds does for coral health,” she said.
First-ever field measurements
Hansel believes the dark shadow cast on superoxide stems from a lack of direct measurements. “To date, our understanding of the role these molecules play in coral health is based on indirect lab measurements of superoxide inside coral tissue. No one had ever attempted direct measurements of superoxide produced outside corals living within reefs. This is most likely because superoxide is very difficult to measure as it is highly reactive and has a lifespan of only roughly 30 seconds in natural waters. You can’t just take the samples back to the lab for analysis.”
To overcome this, she and her research team devised a novel approach for taking real-time measurements of coral superoxide production in a natural reef environment. During a week-long field visit to Hawaii’s Kaneohe Bay in October, 2014, they lugged a laboratory instrument used for superoxide analysis onto a tiny motor boat and took samples from six different shallow reef sites.
“The measurements were very tricky to collect as we had to sample superoxide produced by the coral using a small tube held just above the coral surface,” said Hansel. “From there, it had to be pumped up to the instrument on the boat within 30 seconds, before the superoxide was gone. While all this was happening, we had to hold the boat over the corals being measured and keep the boat steady as waves were coming in.”
WHOI microbiologist Amy Apprill was underwater holding the sampling tube in place as her colleagues “shouted out with excitement from seeing the real-time data.” Apprill said it was amazing to see wide variations in superoxide production among different coral species, some making “a ton” of superoxide, while others making very little. Their analysis showed the corals producing more superoxide had greater resilience to bleaching than the coral producing very little.
Another noteworthy discovery, according to the scientists, was that corals were producing superoxide even when there were no evident stressors, such as hotter seas, which are known to trigger superoxide production.
In a parallel study published November 24 in the journal Frontiers in Marine Science, the team found similar results with corals grown under non-stressful conditions in the lab. The corals, and their microbial partners (symbionts), produced high levels of superoxide at the surface independent of temperature and other variables such as time of day or presence of light.
“This made our eyes open a little bit wider,” Apprill added, “and reinforced the idea that, while we have a better understanding of the negative impacts associated with internally-produced superoxide, the role of superoxide produced outside cells has been overlooked and is not been well understood.”
Playing a positive role
The possibility that superoxide may help corals resist bleaching was eye opening for the scientists, but it isn’t the first time these toxins have proven beneficial to organisms. In fact, research conducted on bacteria and fungi has shown that superoxide is purposely made outside the cell to stimulate cell growth, increase nutrient uptake, and fend off invasive pathogens.
“Superoxide is not always bad,” said Hansel. “In fact, it is an essential molecule that all organisms need. Similar to other organisms, we believe that these compounds may be an integral component of the physiology and immune system of corals. It’s not as black and white as once believed.”
Next steps
Understanding the positive impacts of superoxide on corals may be a stepping stone towards improving coral health and developing bleaching mitigation strategies in the future—particularly if the molecules are in fact protecting corals from stress rather than inducing it. The information could ultimately be used to help determine how to engineer corals to be more resilient. But Hansel feels more work is needed.
“The next step is to conduct a temporal study in the field to get more information on how superoxide is being regulated over time as a function of stress and during the course of a bleaching event,” she said. “This includes when they’re completely healthy, as warmer temperatures increase and stress begins, during peak stress and bleaching, and through recovery. We’d also like to couple this with controlled lab studies where we can grow corals that range in bleaching susceptibility and introduce them to stressors including pathogens to see if they trigger superoxide production. We want to mimic a range of natural conditions in the lab to tease out the benefits superoxide is providing.”
Hansel said that while the fieldwork made it possible to explore corals in a natural environment that is more realistic to the conditions they experience, lab experiments allow them to change one variable at a time while keeping everything else constant so direct relationships can more easily be seen.
“To truly link variables like heat and stress, we need to minimize variability in other variables, like light, changes in flow patterns, and nutrient inputs,” she said.
According to Apprill, the new findings suggest that superoxide may play a variety of roles in coral health, and have led to a new realization of the complexities the toxins play in corals.
“Coral bleaching is one of the biggest problems facing the ocean today,” said Apprill. “We understand the factors that contribute to bleaching events, but the mechanisms appear to be more complicated than we had thought. Fortunately, corals are a really good system to focus on in terms of studying the health impacts of superoxide, since drastic changes in coral health are very visible and can be quickly seen—even from space.”
This research was funded by the National Science Foundation, the Sidney Stern Memorial Trust, the Ocean and Climate Change Institute of the Woods Hole Oceanographic Institution, and an anonymous donor.
For decades, marine chemists have faced an elusive paradox. The surface waters of the world’s oceans are supersaturated with the greenhouse gas methane, yet most species of microbes that can generate the gas can’t survive in oxygen-rich surface waters. So where exactly does all the methane come from? This longstanding riddle, known as the “marine methane paradox,” may have finally been cracked thanks to a new study from the Woods Hole Oceanographic Institution (WHOI).
According to WHOI geochemist Dan Repeta, the answer may lie in the complex ways that bacteria break down dissolved organic matter, a cocktail of substances excreted into seawater by living organisms.
In a paper released in the November 14, 2016 issue of the journal Nature Geoscience, Repeta and colleagues at the University of Hawaii found that much of the ocean’s dissolved organic matter is made up of novel polysaccharides—long chains of sugar molecules created by photosynthetic bacteria in the upper ocean. Bacteria begin to slowly break these polysaccharides, tearing out pairs of carbon and phosphorus atoms (called C-P bonds) from their molecular structure. In the process, the microbes create methane, ethylene, and propylene gasses as byproducts. Most of the methane escapes back into the atmosphere.
“All the pieces of this puzzle were there, but they were in different parts, with different people, in different labs, at different times,” says Repeta. “This paper unifies a lot of those observations.”
Methane is a potent greenhouse gas, and it is important to understand the various sources of methane in the atmosphere. The research team’s findings describe a totally new pathway for the microbial production of methane in the environment, that is very unlike all other known pathways.
Leading up to this study, researchers like Repeta had long suspected that microbes were involved in creating methane in the ocean, but were unable to identify the exact ones responsible.
“Initially, most researchers looked for microbes living in isolated low-oxygen environments, like the guts of fish or shrimp, but they pretty quickly realized that couldn’t be a major factor. Too much oxygenated water flows through there,” says Repeta. Many researchers also examined flocculent material—snowy-looking bits of animal excrement and other organic material floating in ocean waters. “Some of those also have low-oxygen conditions inside them,” he says, “but ultimately they didn’t turn out to be a major methane source either.”
In 2009, one of Repeta’s co-authors, David Karl, found an important clue to the puzzle. In the lab, he added a manmade chemical called methylphosphonate, which is rich in C-P bonds, to samples of seawater. As he did, bacteria within the samples immediately started making methane, proving that they were able to take advantage of the C-P bonds provided by the chemical. Since methylphosphonate had never been detected in the ocean, Repeta and his team reasoned that bacteria in the wild must be finding another natural source of C-P bonds. Exactly what that source was, however, remained elusive.
After analyzing samples of dissolved organic matter from surface waters in the northern Pacific, Repeta ran into a possible solution. The polysaccharides within it turned out to have C-P bonds identical to the ones found in methylphosphonate—and if bacteria could break down those molecules, they might be able to access the phosphorus contained within it.
To confirm this idea, Repeta and his team incubated seawater bacteria under different conditions, adding nutrients such as glucose and nitrate to each batch. Nothing seemed to help the bacteria produce methane—until, that is, they added pure polysaccharides isolated from seawater. Once those were in the mix, the bacteria’s activity spiked, and the vials began spitting out large amounts of methane.
“That made us think it’s a two-part system. You have one species that makes C-P bonds but can’t use them, and another species that can use them but not make them,” he says.
Repeta and another co-author, Edward DeLong, a microbial oceanographer at the University of Hawaii, then began to explore how bacteria metabolize dissolved organic matter. Using a process called metagenomics, DeLong catalogued all the genes he could find in a sample of seawater from the north Pacific. In the process, he found genes responsible for breaking apart C-P bonds, which would allow bacteria to wrench phosphorus away from carbon atoms. Although DeLong was not certain which bacteria could actually do this, one thing was clear: If the gene was active, it would give an organism access to an important but rare nutrient in seawater.
“The middle of the ocean is a nutrient-limited system,” says Repeta. “To make DNA, RNA, and proteins, you need nitrogen and phosphorus, but in the open ocean, those nutrients are at such low concentrations that they’re almost immeasurable.” Instead of using free-floating nutrients in the water, Repeta says, DeLong’s study showed that the microbes must somehow be able to crack into nitrogen and phosphorus hidden deep inside organic molecules.
Although Repeta’s latest paper confirms that it is indeed possible for bacteria to break apart C-P bonds, he notes that it’s still not a particularly easy means of getting nutrients. With phosphorus tied up in organic molecules, it can be exceedingly difficult for bacteria to reach. If microbes can find other sources of the nutrient, he says, they will inevitably use those first.
“Think of it like a buffet,” Repeta says. “If you’re a microbe, inorganic nutrients are like fruits and meats and all the tasty stuff that you reach for immediately. Organic nutrients are more like leftover liver. You don’t really want to eat it, but if you’re hungry enough, you will. It takes years for bacteria to get around to eating the organic phosphorus in the upper ocean. We don’t exactly know why, but there’s another really interesting story there if we can figure it out.”
Also collaborating on the study were Sara Ferrón and Oscar Sosa from the the University of Hawaii, Carl Johnson and Marianne Acker of the Woods Hole Oceanographic Institution, and Lucas Repeta of the University of California, Los Angeles.
The research was supported by the Gordon and Betty Moore Foundation, the Simons Foundation and the National Science Foundation.
The Woods Hole Oceanographic Institution is a private, non-profit organization on Cape Cod, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the oceans and their interaction with the Earth as a whole, and to communicate a basic understanding of the oceans’ role in the changing global environment. For more information, please visit www.whoi.edu.
The Camille and Henry Dreyfus Foundation selected Mak Saito, a biogeochemist at Woods Hole Oceanographic Institution (WHOI), as one of eight awardees of a 2016 Postdoctoral Program in Environmental Chemistry grant.
The program provides leading U.S. faculty in the environmental chemical sciences with $120,000 over two years to appoint a postdoctoral Dreyfus Fellow to work in their labs.
“The Foundation initiated this program in 1996, in recognition of chemistry’s central role in matters of environmental importance,” said Mark J. Cardillo, executive director of The Camille and Henry Dreyfus Foundation. “After training with an established principle investigator, former Dreyfus Fellows have gone on to conduct environmental research at many of the nation’s leading institutions.”
“We’re very honored to receive support from the Camille and Henry Dreyfus Foundation’s program in Environmental Chemistry,” said Saito. “It’s an exciting time in environmental research, where the technical capabilities are rapidly becoming much more sophisticated, opening all kinds of doors to discovery regarding the mysteries of the oceans.”
Saito’s research focuses on the nutritional requirements of marine microbes, with an emphasis on metals needed for protein synthesis. Metals are essential components in biogeochemical reactions, and their intense scarcity in seawater can have a profound effect on major natural cycles, such as the carbon and nitrogen cycles, and has resulted in unique adaptations.
Saito developed and adapted sophisticated methods for understanding nutrient-microbial interactions using proteomics—a branch of biochemistry that allows studies of the thousands of proteins encoded by a genome present in an organism—and high-throughput sampling and analytical methods for low-level trace metal measurements in different parts of the ocean.
“We plan to bring in a promising postdoctoral researcher with interests in studying metalloproteins and metal transporters in marine microbes,” Saito said. “These studies will help foster our ability to conduct diagnosis of ocean ecosystems and their responses to environmental changes, as well as identifying key cellular components needed for future synthetic biological applications such as algal biofuel production.”
“Mak Saito’s work is truly at the cutting edge of the study of metals and microbes,” said WHOI President and Director Mark Abbott. “This award from the Camille and Henry Dreyfus Foundation is well-deserved.”
The Camille and Henry Dreyfus Foundation is a leading non-profit organization devoted to the advancement of the chemical sciences. It was established in 1946 by chemist, inventor, and businessman Camille Dreyfus, who directed that the foundation’s purpose be “to advance the science of chemistry, chemical engineering and related sciences as a means of improving human relations and circumstances around the world.”
The Woods Hole Oceanographic Institution is a private, non-profit organization on Cape Cod, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate a basic understanding of the ocean’s role in the changing global environment. For more information, please visit www.whoi.edu.
Five years after the Fukushima nuclear accident, there is still no U.S. federal agency responsible for studies of radioactive contaminants in the ocean. But scientific data about the levels of radioactivity in the ocean off our shores are available publicly thanks to ongoing efforts of independent researchers, including Ken Buesseler, a radiochemist with Woods Hole Oceanographic Institution (WHOI), who has led the effort to create and maintain an ocean monitoring network along the U.S. West Coast.
Since 2011, Buesseler has received contributions from citizens, small businesses, foundations and large companies to enable the sampling of nearly 1000 seawater samples for Fukushima radionuclides. Buesseler has been involved in seven cruises off Japan, sampling off Fukushima at least once every year, most recently in October 2015, and has published 19 peer-reviewed papers based on his analysis of seawater and sediments from the Pacific.
Buesseler’s work reveals that levels of radioactive forms of cesium in the ocean off Japan are thousands of times lower than during the peak releases in 2011, however, his analysis of cesium and strontium indicate releases from the plant are not yet “under control,” a statement that has been used by the Japanese government to describe the situation when levels are below regulatory limits.
“To date, we have focused our efforts on testing for the two isotopes of cesium (137 and 134) and strontium,” says Buesseler. “The cesium isotopes were the most abundant after the accident and provide the first indication of whether contamination from Fukushima is present in a seawater sample.” Because cesium-134 has a half-life of just two years, researchers know, when detected, that it comes from Fukushima. Cesium was 40 times more abundant in the water after the accident than strontium – a ratio that the scientists discover is changing.
The changing concentrations of both these elements in the waters off Japan tell a story of continued small leaks and raise concerns about the materials still stored at the reactor site.
Cesium off Japan
Cesium levels in the water off Japan spiked after the accident, then fell dramatically in the following year. Since then, however, rather than a steady decline, the cesium levels have remained relatively constant.
“Levels today off Japan are thousands of times lower than during the peak releases in 2011,” says Buesseler. “But we are not seeing the steady decrease we would expect to see off Fukushima if all sources had stopped; rather, we are finding values are still elevated, which confirms that there is continued release from the plant.”
The highest level of cesium Buesseler’s team found in a sample taken off Japan in October 2015 measured 200 Becquerels per cubic meter (about 264 gallons) of seawater. (A Becquerel equals one decay event per second.) The samples were collected following a typhoon in September that delivered unusually heavy rains, which the researchers suspect may have caused elevated cesium levels in the ocean. These levels are still higher than prior to the accident but much lower than at the peak of the releases in 2011 when there were 50 million Bq/m3 in the ocean immediately off the dock at Fukushima.
While not declining as quickly as researchers had expected, the levels detected near Japan are still more than 40 times lower than US government safety limits for drinking water, and well below limits of concern for direct exposure while swimming, boating, or other recreational activities. At these lower levels, the concern remains for seafood safety and internal consumption of radioactive contaminants in fish.
Strontium off Japan
The scientists have learned that cesium is just part of the story: Strontium, too, is not falling as expected. Strontium-90 has nearly the same half-life of cesium-137, and the researchers expected its levels would drop in step with cesium. Yet Buesseler and colleagues led by Universitat Autònoma of Barcelona, Spain have found that strontium is not decreasing as fast as cesium. Whereas there was approximately 40 times more cesium than strontium in the waters off Japan in 2011, by 2013, there was approximately 10 times more cesium than strontium. The concern lies in the thousands of tons of strontium still stored in tanks at the nuclear power plant and accumulated in buildings and soils, some of it still leaking into the ocean.
“We think that when there is heavy rain, more cesium, strontium, and other isotopes from the nuclear power plant are carried into the ocean,” says Buesseler. “We are still investigating how that occurs –whether carried in the groundwater or from the run off of sediment – but clearly it is highest near the contaminated site of the Fukushima nuclear power plants.”
Because strontium-90 mimics calcium in humans and animals, it is taken up by and concentrated in bones, where it remains for long periods of time, making it a greater health concern than cesium. Cesium, on the other hand, flushes out of the body much faster.
“Whereas it takes approximately two months for half of the radioactive cesium to flush out of fish, it takes more like two years for strontium to flush out of fish because it’s in their bones,” says Buesseler. “So if the supply of strontium to the ocean gets worse, it would take longer for the levels to decrease in seafood. So far, strontium levels are more than a hundred times lower than cesium when measured in fish, so it has not been a concern, but we have to monitor it.”
Monitoring the North American West Coast
In addition to studying the waters off Japan, Buesseler and his colleagues have been actively monitoring the Pacific waters off the North American West Coast, primarily for cesium, the most abundant element after the accident. So far, they have detected only minute quantities of Fukushima cesium.
Fukushima-derived cesium first arrived along the west coast of North America in February 2015, measuring 6 Bq/m3 in Ucluelet, British Columbia. The highest numbers the researchers have seen in the eastern Pacific are almost 10 Bq/m3, found some 1,500 miles north of Hawaii.
“If you were to swim in waters at this level the health effects, or dose, would be 1000 times less than a single dental x-ray. This is not zero, but a very small risk that would not stop me from swimming or eating seafood from our side of the Pacific,” said Buesseler.
Because cesium levels have been so small and the cost of analyzing samples for strontium is so great, the researchers have not been analyzing samples off North America for strontium, until recently.
The researchers receive enough questions about strontium that they re-analyzed some of the West Coast samples that contained Fukushima cesium-134 looking for strontium, and have not detected any above the background levels that were there before Fukushima.
“So little strontium was released relative to cesium from Fukushima in 2011, that even though Fukushima cesium is detectable, the strontium-90 signal is not detectable in these samples, at least in the eastern Pacific,” says Buesseler.
The researchers continue to collect and analyze samples both from citizen scientists and, when possible, from ships and research cruises on the eastern side of the Pacific. The data are made publically available through the Our Radioactive Ocean, the crowd-funding website Buesseler created for this purpose. The site’s map interface allows the public to see where samples were collected and the cesium values measured in each sample.
Levels in the ocean are expected to peak along the West Coast of the U.S. some time in 2015 or 2016, so continued monitoring is needed.
The Woods Hole Oceanographic Institution is a private, non-profit organization on Cape Cod, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate a basic understanding of the ocean’s role in the changing global environment. For more information, please visit www.whoi.edu.
Scientists monitoring the spread of radiation in the ocean from the Fukushima nuclear accident report finding an increased number of sites off the US West Coast showing signs of contamination from Fukushima. This includes the highest detected level to date from a sample collected about 1,600 miles west of San Francisco. The level of radioactive cesium isotopes in the sample, 11 Becquerel’s per cubic meter of seawater (about 264 gallons), is 50 percent higher than other samples collected along the West Coast so far, but is still more than 500 times lower than US government safety limits for drinking water, and well below limits of concern for direct exposure while swimming, boating, or other recreational activities.
Ken Buesseler, a marine radiochemist with the Woods Hole Oceanographic Institution (WHOI) and director of the WHOI Center for Marine and Environmental Radioactivity, was among the first to begin monitoring radiation in the Pacific, organizing a research expedition to the Northwest Pacific near Japan just three months after the accident that started in March 2011. Through a citizen science sampling effort, Our Radioactive Ocean, that he launched in 2014, as well as research funded by the National Science Foundation, Buesseler and his colleagues are using sophisticated sensors to look for minute levels of ocean-borne radioactivity from Fukushima. In 2015, they have added more than 110 new samples in the Pacific to the more than 135 previously collected and posted on the Our Radioactive Ocean web site.
“These new data are important for two reasons,” said Buesseler. “First, despite the fact that the levels of contamination off our shores remain well below government-established safety limits for human health or to marine life, the changing values underscore the need to more closely monitor contamination levels across the Pacific. Second, these long-lived radioisotopes will serve as markers for years to come for scientists studying ocean currents and mixing in coastal and offshore waters.”
The recent findings reported by Buesseler agree with those reported by scientists who are part of the group Kelp Watch and by the team of Canadian scientists working under the InFORM umbrella. While Buesseler’s work focuses on ocean chemistry and does not involve sampling of biological organisms, the InFORM scientists have done sampling of fish and have not seen any Fukushima cesium in fish collected in British Columbia.
Almost any seawater sample from the Pacific will show traces of cesium-137, an isotope of cesium with a 30-year half-life, some of which is left over from nuclear weapons testing carried out in the 1950s to 1970s. The isotope cesium-134 is the “fingerprint” of Fukushima, but, with a 2-year half-life, it decays much quicker than cesium-137. Scientists back calculate traces of cesium-134 to determine how much was actually released from Fukushima in 2011 and add to it an equal amount of cesium-137 that would have been released at the same time.
Working with Japanese colleagues, Buesseler also continues to independently monitor the ongoing leaks from Fukushima Dai-ichi by collecting samples from as close as one kilometer (one-half mile) away from the nuclear power plants. During his most recent trip this October they collected samples of ocean water, marine organisms, seafloor sediment and groundwater along the coast near the reactors. Buesseler says the levels of radioactivity off Fukushima remain elevated – some 10 to 100 times higher than off the US West Coast today, and he is working with colleagues at WHOI to try to determine how much radioactive material is still being released to the ocean each day.
“Levels today off Japan are thousands of times lower than during the peak releases in 2011. That said, finding values that are still elevated off Fukushima confirms that there is continued release from the plant,” said Buesseler.
Buesseler will present his latest findings on the spread of Fukushima radiation at the American Geophysical Union conference in San Francisco on Dec. 14, 2015.
The Woods Hole Oceanographic Institution is a private, non-profit organization on Cape Cod, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate a basic understanding of the ocean’s role in the changing global environment. For more information, please visit www.whoi.edu.
Imagine being in a car with the gas pedal stuck to the floor, heading toward a cliff’s edge. Metaphorically speaking, that’s what climate change will do to the key group of ocean bacteria known as Trichodesmium, scientists have discovered.
Trichodesmium (called “Tricho” for short by researchers) is one of the few organisms in the ocean that can “fix” atmospheric nitrogen gas, making it available to other organisms. It is crucial because all life – from algae to whales – needs nitrogen to grow.
A new study from University of Southern California and Woods Hole Oceanographic Institution (WHOI) shows that changing conditions due to climate change could send Tricho into overdrive with no way to stop – reproducing faster and generating lots more nitrogen. Without the ability to slow down, however, Tricho has the potential to gobble up all its available resources, which could trigger die-offs of the microorganism and the higher organisms that depend on it.
By breeding hundreds of generations of the bacteria over the course of nearly five years in high carbon dioxide ocean conditions predicted for the year 2100, researchers found that increased ocean acidification evolved Tricho to work harder, producing 50 percent more nitrogen, and grow faster.
The problem is that these amped-up bacteria can’t turn it off even when they are placed in conditions with less carbon dioxide. Further, the adaptation can’t be reversed over time – something not seen before by evolutionary biologists, and worrisome to marine biologists, says David Hutchins, lead author of the study.
“Losing the ability to regulate your growth rate is not a healthy thing,” said Hutchins, professor at the USC Dornsife College of Letters, Arts and Sciences. “The last thing you want is to be stuck with these high growth rates when there aren’t enough nutrients to go around. It’s a losing strategy in the struggle to survive.”
Tricho needs phosphorous and iron, which also exist in the ocean in limited supply. With no way to regulate its growth, the turbo-boosted Tricho could burn through all of its available nutrients too quickly and abruptly die off, which would be catastrophic for all other life forms in the ocean that need the nitrogen it would have produced to survive.
Some models predict that increasing ocean acidification will exacerbate the problem of nutrient scarcity by increasing stratification of the ocean – locking key nutrients away from the organisms that need them to survive.
Hutchins is collaborating with Eric Webb of USC Dornsife and Mak Saito of WHOI to gain a better understanding of what the future ocean will look like, as it continues to be shaped by climate change. They were shocked by the discovery of an evolutionary change that appears to be permanent – something Hutchins described as “unprecedented.”
“Tricho has been studied for ages. Nobody expected that it could do something so bizarre,” he said. “The evolutionary biologists are interested in it just to study this as a basic evolutionary principle.”
The team is now studying the DNA of Tricho to try to find out how and why the irreversible evolution occurs. Earlier this year, research led by Webb found that Tricho’s DNA inexplicably contains elements that are usually only seen in higher life forms.
“Our results in this and the aforementioned study are truly surprising. Furthermore, they are giving us an improved, view of how global climate change will impact Trichodesmium and the vital supplies of new nitrogen it provides to the rest of the marine food web in the future,” Webb said.
“There’s a lot of interest in understanding how organisms will respond to increasing CO2,” said Mak Saito, a co-author on the study from the Woods Hole Oceanographic Institution. “These findings are quite surprising in determining that the important marine microbe Trichodesmium adapts to high CO2, but can’t revert back once CO2 is reduced again. This has implications not only for our understanding of the evolution and biochemical processes that underlie this irreversible change, but also for policy makers emphasizing the urgency of acting to reduce fossil fuel emissions sooner rather than later.”
The research was funded by the National Science Foundation and was published in Nature Communications on Sept. 1, 2015.
The Woods Hole Oceanographic Institution is a private, non-profit organization on Cape Cod, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate a basic understanding of the ocean’s role in the changing global environment. For more information, please visit www.whoi.edu.
Ancient rocks harbored microbial life deep below the seafloor, reports a team of scientists from the Woods Hole Oceanographic Institution (WHOI), Virginia Tech, and the University of Bremen. This new evidence was contained in drilled rock samples of Earth’s mantle – thrust by tectonic forces to the seafloor during the Early Cretaceous period. The new study was published today in the Proceedings of the National Academy of Sciences.
The discovery confirms a long-standing hypothesis that interactions between mantle rocks and seawater can create potential for life even in hard rocks deep below the ocean floor. The fossilized microbes are likely the same as those found at the active Lost City hydrothermal field, providing potentially important clues about the conditions that support ‘intraterrestrial’ life in rocks below the seafloor.
“We were initially looking at how seawater interacts with mantle rocks, and how that process generates hydrogen,” said Frieder Klein, an associate scientist at WHOI and lead author of the study. “But during our analysis of the rock samples, we discovered organic-rich inclusions that contained lipids, proteins and amino acids – the building blocks of life – mummified in the surrounding minerals.”
This study, which was a collaborative effort between Klein, WHOI scientists Susan Humphris, Weifu Guo and William Orsi, Esther Schwarzenbach from Virginia Tech and Florence Schubotz from the University of Bremen, focused on mantle rocks that were originally exposed to seawater approximately 125 million years ago when a large rift split the massive supercontinent known as Pangaea. The rift, which eventually evolved into the Atlantic Ocean, pulled mantle rocks from Earth’s interior to the seafloor, where they underwent chemical reactions with seawater, transforming the seawater into a hydrothermal fluid.
“The hydrothermal fluid likely had a high pH and was depleted in carbon and electron acceptors,” Klein said. “These extreme chemical conditions can be challenging for microbes. However, the hydrothermal fluid contained hydrogen and methane and seawater contains dissolved carbon and electron acceptors. So when you mix the two in just the right proportions, you can have the ingredients to support life.”
According to Dr. Everett Shock, a professor at Arizona State University’s School of Earth and Science Exploration, the study underscores the influence major geologic processes can have on the prospect for life.
“This research makes the connection all the way from convection of the mantle to the break-up of the continents to ultimately providing geochemical options for microbiology,” Shock said. “It’s just such a nice demonstration of real-world geobiology with a lot of ‘geo’ in it.”
Drilling Deep
The rock samples analyzed in the study were originally drilled from the Iberian continental margin off the coast of Spain and Portugal in 1993. During the expedition aboard the research vessel JOIDES Resolution operated by the Ocean Drilling Program (ODP) – researchers drilled through 690 meters of mud and sediment deposited onto to the ocean floor to reach the ancient seafloor created during the break-up of the supercontinent Pangaea and the opening of the Atlantic Ocean. The drill samples had been stored in core repositories at room temperature for more than two decades, before Klein and his colleagues began their investigation and discovered the fossilized microbial remains.
“Colonies of bacteria and archaea were feeding off the seawater-hydrothermal fluid mix and became engulfed in the minerals growing in the fractured rock,” Klein said. “This kept them completely isolated from the environment. The minerals proved to be the ultimate storage containers for these organisms, preserving their lipids and proteins for over 100 million years.”
“It’s exciting that the research team was able to go back and examine samples that had been collected years ago for other reasons and find new discoveries,” Shock said. “There will always be active new drilling, but this study raises the possibility of there being a lot more out there in the way of existing samples that could be analyzed.”
In the lab, samples from the rock interior had to be extracted since the outside of the drill core was stored under non-sterile conditions. So Klein and his colleagues took a number of careful steps to ensure the integrity of the sample interior wasn’t compromised, and then analyzed the rocks with high-resolution microscopes, a confocal Raman spectrometer and a range of isotope techniques.
A Link to the Lost City
While Raman spectroscopy enabled Klein to verify the presence of amino acids, proteins and lipids in the samples, it did not provide enough detailed information to correlate them with other hydrothermal systems. The lipids were of particular interest to Klein since they tend to be better preserved over long timescales, and have been studied in a wide range of seafloor environments. This prompted Klein to ask Schubotz, an expert in lipid biomarker analysis at MARUM – Center for Marine Environmental Sciences, University of Bremen, if she could tease out further information about the lipids from these ancient rocks.
Schubotz ran the lipids through an advanced liquid chromatography-based mass spectrometer system to separate out and identify their biochemical components. The analysis led to a remarkable discovery: the lipids from the Iberian margin match up with those from the Lost City hydrothermal field, which was discovered in 2000 in the Mid-Atlantic Ridge during an expedition on board the WHOI-operated research vessel Atlantis. This is significant because researchers believe the Lost City is a present-day analog to ancient hydrothermal systems on early Earth where life may have emerged.
“I was stoked when I saw Dr. Schubotz’s email detailing the analytical results,” Klein said. “It was fascinating to find these particular biological substances – which had previously been found only at the Lost City hydrothermal field and in cold seeps – in rocks below the seafloor where life is extremely challenging. At that point we knew we were onto something really cool!”
A Deeper Understanding
According to Klein, confirmation that life is possible in mantle rocks deep below the seafloor may have important implications for understanding subseafloor life across a wide range of geologic environments.
“All the ingredients necessary to drive these ecosystems were made entirely from scratch,” he said. “Similar systems have likely existed throughout most of Earth’s history to the present day and possibly exist(ed) on other water-bearing rocky planetary bodies, such as Jupiter’s moon Europa.”
The study reinforces the idea that life springs up anywhere there is water, even in seemingly hostile geological environments – a tantalizing prospect as scientists find more and more water elsewhere in the solar system. But Klein contends that, while scientists have long understood many of the forces driving microbial life above the seafloor, there is still a great deal of uncertainty when it comes to understanding biogeochemical processes occurring in the oceanic basement.
“In the future, we’ll be trying to learn more about these particular microorganisms and what the environmental conditions were in the mixing zone in that location. We also plan to go to different places where we think similar processes may have taken place, such as along the Newfoundland margin, and analyze samples to see if we find similar signatures. Broadening this research could provide additional insights about Earth’s history and the search for life in the solar system.”
This study was funded by the Ocean Exploration Institute (OEI) at Woods Hole Oceanographic Institution.
The Woods Hole Oceanographic Institution is a private, non-profit organization on Cape Cod, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate a basic understanding of the ocean’s role in the changing global environment. For more information, please visit www.whoi.edu.
An international research team reports results of a three-year study of sediment samples collected offshore from the Fukushima Daiichi Nuclear Power Plant in a new paper published August 18, 2015, in the American Chemical Society’s journal, Environmental Science and Technology.
The research aids in understanding what happens to Fukushima contaminants after they are buried on the seafloor off coastal Japan.
Led by Ken Buesseler, a senior scientist and marine chemist at the Woods Hole Oceanographic Institution (WHOI), the team found that a small fraction of contaminated seafloor sediments off Fukushima are moved offshore by typhoons that resuspend radioactive particles in the water, which then travel laterally with southeasterly currents into the Pacific Ocean.
“Cesium is one of the dominant radionuclides that was released in unprecedented amounts with contaminated water from Japan’s Fukushima Daiichi nuclear power plant following the March 11, 2011, earthquake and tsunami,” says Buesseler. “A little over 99 percent of it moved with the water offshore, but a very small fraction—less than one percent—ended up on the sea floor as buried sediment.”
“We’ve been looking at the fate of that buried sediment on the continental shelf and tracking how much of that contaminated sediment gets offshore through re-suspension from the ocean bottom,” he adds.
The research team, which included colleagues from the Japan Agency for Marine-Earth Science and Technology and the Japan Atomic Energy Agency, analyzed three years’ worth of data collected from time-series sediment traps.
Researchers deployed the pre-programmed, funnel-shaped instruments 115 kilometers (approximately 70 miles) southeast of the nuclear power plant at depths of 500 meters (1,640 feet) and 1,000 meters (3,280 feet). The two traps began collecting samples on July 19, 2011—130 days after the March 11th earthquake and tsunami—and were recovered and reset annually.
After analyzing the data, researchers found radiocesium from the Fukushima Daiichi Nuclear Power Plant accident in the sediment samples along with a high fraction of clay material, which is characteristic of shelf and slope sediments suggesting a near shore source.
“This was a bit of a surprise because when we think of sediment in the ocean, we think of it as sinking vertically, originating from someplace above. But what this study clearly shows is that the only place that the material in our sediment traps could have come from was the continental shelf and slope buried nearshore. We know this because the coastal sediments from the shelf have a unique Fukushima radioactive and mineral signal,” says Buesseler.
The data also revealed that peak movements of the sediments with radiocesium coincided with passing typhoons which likely triggered the resuspension of coastal sediments. Radiocesium was still detected in sediment samples from July 2014.
“The total transport is small, though it is readily detectable. One percent or less of the contaminated sediment that’s moving offshore every year means things aren’t going to change very fast,” Buesseler says. “What’s buried is going to stay buried for decades to come. And that’s what may be contributing to elevated levels of cesium in fish—particularly bottom-dwelling fish off Japan.”
While there were hundreds of different radionuclides released from the Fukushima Daiichi Nuclear Power Plant during the disaster, after the initial decay of contaminants with half lives (the time it takes for one half of a given amount of radionuclide to decay) less than days to weeks, much of the attention has remained focused on cesium-137 and-134— two of the more abundant contaminants. Cesium-134 has a half-life of a little over two years, and so any found in the ocean could come only from the reactors at Fukushima. Cesium-137 has a half-life of roughly 30 years and is also known to have entered the Pacific as a result of aboveground nuclear weapons tests in the 1950s and ‘60s, providing a benchmark againstwhich to measure any additional releases from the reactors.
In October, Buesseler and the research team will return to Japan to redeploy more sediment traps. The continued study will help estimate how long it takes to decrease the level of radiocesium in seafloor sediments near the Fukushima Daiichi Nuclear Power Plant.
The research was funded initially by a Rapid Response Grant from the National Science Foundation, and continued for three years through support from the Deerbook Charitable Trust and Gordon and Betty Moore Foundation.
The Woods Hole Oceanographic Institution is a private, non-profit organization on Cape Cod, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate a basic understanding of the ocean’s role in the changing global environment. For more information, please visit www.whoi.edu.
As temperatures rise, some of the organic carbon stored in Arctic permafrost meets an unexpected fate—burial at sea. As many as 2.2 million metric tons of organic carbon per year are swept along by a single river system into Arctic Ocean sediment, according to a new study an international team of researchers published today in Nature. This process locks away carbon dioxide (CO2) – a greenhouse gas – and helps stabilize the earth’s CO2 levels over time, and it may help scientists better predict how the natural carbon cycle will interplay with the surge of CO2 emissions due to human activities.
“The erosion of permafrost carbon is very significant,” says Woods Hole Oceanographic Institution (WHOI) Associate Scientist Valier Galy, a co-author of the study. “Over thousands of years, this process is locking CO2 away from the atmosphere in a way that amounts to fairly large carbon stocks. If we can understand how this process works, we can predict how it will respond as the climate changes.”
Permafrost—frozen ground found in the Arctic and in some alpine regions—is known to hold billions of tons of organic material. Amid concerns about rising Arctic temperatures and their impact on permafrost, many researchers have directed their efforts to studying the permafrost carbon cycle—the processes through which carbon circulates between the atmosphere, the soil and plants (the biosphere), and the sea. Yet how this cycle works and how it responds to the warming, changing climate remains poorly understood.
Galy and his colleagues from Durham University, the Institut de Physique du Globe de Paris, the NERC Radiocarbon Facility, Stockholm University, and the Universite Paris-Sud set out to characterize the carbon cycle in one particular piece of the Arctic landscape—northern Canada’s Mackenzie River, the largest river flowing into the Arctic Ocean from North America and that ocean’s greatest source of sediment. The researchers hypothesized that the Mackenzie’s muddy water might erode soils along its path, some from places where permafrost is melting, and wash that biosphere-derived material and the organic carbon within it into the ocean, preventing the degradation of organic carbon and associated release of CO2 into the atmosphere.
The researchers collected samples at various depths and locations along the river system, lowering a specially-designed device to take samples of the water and suspended sediments carried by the river. To take into consideration the river’s seasonal variation—its flow increases sharply during the spring, when warm temperatures melt the snowpack and raise water levels, and drops during the frozen winter months—they sampled it during different seasons across three years starting in 2009.
Then the researchers sifted through the samples to isolate the carbon they contained. They used the presence of one specific isotope of carbon that decays over time, carbon-14, to determine how old the carbon was. This was important because it revealed the carbon’s origin– rock or biosphere.
“The carbon that comes from the rocks has been there for hundreds of thousands, sometimes millions of years,” Galy says. “The other carbon can come from a tree that fell into the river two days before we sampled or from the permafrost and be thousands years old.”
The carbon from rocks has been stored away from the atmosphere for a long time, and exists in a form that makes it less likely to react with its environment and enter the atmosphere. But the newer, biosphere-based carbon is more labile and likely to react, potentially entering the atmosphere and raising CO2 levels.
“If you bury the biosphere-based carbon, you have an actual carbon sink—you’re taking carbon that could be out in the atmosphere and locking it away,” Galy says.
The researchers compared what they found along the river to a sediment core obtained from the Arctic Ocean seabed at the Mackenzie delta, tracing the rock and biosphere carbon to the sediment deposits there. They found that a significant amount of the biosphere carbon—more than that carried by all the major Eurasian Arctic rivers combined—is swept into storage offshore. Using carbon-14 they further determined that this biosphere-derived carbon is up to 9000 years old, a clearly indication of its permafrost origin.
“That carbon is not returning to the atmosphere for a long time,” says Robert Hilton, associate professor at Durham University who worked on the study. “Over geological timescales, warming conditions lead to the sequestration of that carbon at sea.”
This sequestration likely kept naturally-occurring CO2 levels in check. But the researchers emphasize that this natural process is 10 to 20 times too slow to keep pace with CO2 emissions from human activities, such as the burning of fossil fuels.
“River transfer is not going to solve the problem—it’s not going to make the CO2 we inject into the atmosphere go away,” Galy says. But the findings do reveal a more complex picture of the relationships between warming temperatures, thawing permafrost and carbon emission—a picture that Galy and his international colleagues hope to further investigate with future studies.
The research was supported by the WHOI Arctic Research Initiative, the Natural Environment Research Council UK, an Early Career Research Grant by the British Society for Geomorphology, a Royal Society University Fellowship, and a grant from the National Science Foundation (OCE-0928582).
The Woods Hole Oceanographic Institution is a private, non-profit organization on Cape Cod, Mass., dedicated to marine research, engineering, and higher education. Established in 1930 on a recommendation from the National Academy of Sciences, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate a basic understanding of the ocean’s role in the changing global environment. For more information, please visit www.whoi.edu.
Oceanus Magazine
福島第一と海:
災害対応の10年間を語る
English Version
On the high seas
Observers join Orpheus cruise thanks to the Neil Armstrong Fund
By Hannah Piecuch
２０１１年３月１１日、日本の都市仙台の東約１２９キロメートルで起きた震度９の地震によって発生した津波は、水柱となって沿岸部に激突し、福島第一原子力発電所を大破した。一万六千人近い人々が犠牲となり、現在も発電所から放射能汚染水が流出している。（撮影：ケン・コステル、©ウッズホール海洋研究所）
２０１１年３月１１日、日本の都市仙台の東約１２９キロメートルで、海底が激しく隆起した。日本を支える構造プレートの下部にゆっくりと沈み込んでいる太平洋プレートによって蓄積された歪みが、突如スライドし跳ね上げられたのである。ほんの一瞬にして、サッカー場の半分もの大きさの海底の一部が水平方向に押しやられ、９メートル以上上昇した。
日本では毎年数百もの地震を経験するのだが、しかし、東北地方太平洋沖地震はこの国が記録した中でも未曾有の大規模なものであった。マグニチュード９の揺れが長くとも６分も続き、本州を２メートル半も東へシフトさせた。
海底が上部大きく突き上げられ発生した津波は、半時間もしないうちに近隣の日本沿岸地域を襲った。街全体が三階立ての建物に匹敵する水壁によって破壊され、一万六千人近い人々が犠牲となった。
福島第一原子力発電所もこの時被災を免れなかった。地震翌日には爆発が起き、拡散される放射性降下物を避けるため、15万人以上の近隣住民が強制的に避難することを余儀なくされた。さらなる放射性物質が海洋に直接流出し、大気中に拡散したものも最終的には海洋表面に降下した。
「このような天災によって海に流出する放射性物質の量としては、福島第一原発事故は、前例のない出来事だったのです。」と、ウッズホール海洋研究所シニアサイエンティストであるケン・ベッセラー博士は話す。「起きたことを振り返り、現状を把握することは非常に重要です。」
三重の災害から１０年目となる今年、ベッセラー博士は世界中の研究者たちと福島での出来事において過去１０年間学んできたこと、さらにどのように状況が引き続き変化するのか、遠隔で議論してきた。
福島第一原子力発電所は、適切に地震に対応するシステムを備えていた。激震によって送電線が破損し、プラントと六基の原子炉が送配電網から遮断され、三基の稼働中の原子炉が自動的に停止した。しかし、原子炉を停止させることは電気を消すように容易なことではない。
「核分裂反応が止まったとしても、放射性物質は熱を発し続けます。」福島県沿岸における研究調査隊を幾度も率いてきた東京海洋大学の神田穣太教授は云う。「かなり長期にわたり水で冷し続けなくてはなりません。」
燃料棒を冷却する水を汲み上げ続けるために、施設は予備発電機に切り替えた。そして、津波が襲った。
原発は海面から9メートル上に掘削された丘陵に建設されていた。その区域で予測されていた津波の高さは最大６メートルであったと、神田教授は云う。しかし、その日襲った津波は11〜１５メートルの間と記録された。それは施設を浸水させ、予備発電を破壊した。
冷却システムが故障したのち、原子炉の炉心の温度が上昇し始めた。原子炉内の燃料棒が過熱し溶解し始め、ウラニウム燃料が露出して格納容器が破損した。同時に原子炉の水が蒸気になり金属製燃料棒に反応して、揮発性の水素ガスが発生した。
炉心内に蓄積した圧力を軽減するため、発電所の作業員たちは数日間にわたり何度かガスを放出した。このガスは放射性同位体、あるいは放射性物質を大気中へ流出したが、それだけでは済まなかった。続く数日の間に原発での三度の水素爆発が今まで以上の放射性物質を空中に放出し、その多くは最終的に海洋上に落下したのである。
緊急隊員たちが過熱した原子炉へ必死に高圧放水砲と消火ホースで噴水し、そして自衛隊のヘリが上空から何百トンもの水を投下させた。こうした水は放射性物質を取り込み、海洋へ溢れ出すか、地面に浸透していき、最終的には海へと運ばれていくこととなった。
地震により福島第一原子力発電所は停電し、津波により予備の発電機が浸水したことで、6基の原子炉のうち3基が過熱溶解し、水素ガスが発生したのち爆発した。放射性物質を含んだ地下水や冷却水は海に流出し、海岸の砂や海底の堆積物に、あるいは魚類やその他の生物に蓄積され、大部分は海流に乗って太平洋を横断した。(福島中央テレビ)
2011年6月に行われた最初の国際調査航海では、福島第一原発付近沿岸から４８２キロメートル以上沖合までの放射性核種の拡散を追跡した。過去10年以上にわたり、科学者、技術者、一般市民が、発電所近海からカナダ及びアメリカ合衆国の西海岸の広範囲において、海水、堆積物、海洋生物のサンプルを採取してきた。（撮影：ケン・コステル、©ウッズホール海洋研究所）
今回の災害で最も著しく放出された放射性同位体は、ヨウ素１３１、セシウム１３４及びセシウム１３７である。これら全ては有害物質の可能性はあるが、それぞれ異なった速度で減衰する。ほとんどのヨウ素１３１は数週間で消失する。２年間の半減期を持つセシウム１３４は10年後わずか３％しか残留しない。しかし急速に減少することを物語ってはいても、福島の海洋への打撃として拭いきれない跡を残した。セシウム１３７、これは３０年の半減期を持つため、減少には何十年もかかる。実際、１９５０〜６０年代に行われた核兵器の大気圏内実験によって放出されたセシウム１３７が、現在もなお世界中の海洋に少量ではあるが計測可能な量存在するのである。
「原子力発電が多くの国で利用され始め、海洋中には常にある程度のセシウムが存在してきましたが、問題は、今回の事故でどのくらい増加したかということです。」２０１１年６月に福島県近海で放射性物質計測のための調査航海を率いたベッセラー博士は語る。「我々は、福島第一原発に近い海洋で、1立方メートルにつき5千万ベクレル以上という極めて高いレベルの放射性セシウム濃度を検知しました。」
１ベクレルは、1秒につき一個の原子核が崩壊するのに等しく、非常に微量の放射能である。世界保健機構（WHO）のガイドラインでは、飲料水に含有されるセシウム１３７の量は１立方メートルにつき1万ベクレル以上でないことを推奨している。災害に見舞われる以前、福島周辺の水質は、１立方メートルにつき約２ベクレルであった。それが、事故直後には５千万を超えるまでに上昇し、その後原発からの放射性物質の流出を食い止めるための対策が功を奏し、数ヶ月で急速に数値は下がった。ある程度の放射性物質は海底の堆積物に累積したが、多くは強い黒潮によって太平洋へと移流拡散され、セシウムが海流にのって北米にまで運ばれてしまうのではないかという恐怖心に火をつけた。
太平洋を横断する福島からの放射性物質の動向を調査するため、ベッセラー博士は西海岸でのセシウムがどのくらいの数値であるかを調査する地域密着型の活動を結成した。彼の研究室は、付近を運行中の船舶から、サーファーたちから、さらには海水浴客から、沿岸域の海水サンプルを入手した。彼らは一部の放射性物質が太平洋を渡って福島から北米まで運ばれてきたことを示す証拠を発見したものの、その数値は１立方メートルにつき１０ベクレル以下という極めて低いものだった。
「非常に小さな数字でした。」ベッセラー博士は云った。「もし仮に１立方メートルにつき約１０ベクレルという水中で一年間毎日海水浴をしたとして、線量、追加被曝は、歯科のレントゲン一回の千分の一程度でしょう。危険性はゼロではありませんが、非常に少量で、西海岸で水泳をしたり、サーフィンやボートで漕ぎだしたりしても、心配することはありません。」
しかしながら、福島における放射性物質の流出は完全に消散したわけではない。震災後の数年間に比べればはるかに少量ではあるが、原子炉からの漏出、河川の放射性堆積物、汚染された地下水が、海洋に流出し続けている。福島近海における放射性物質濃度は、２０１６年以来１立方メートルあたり100ベクレル前後というレベルで停滞している。
突然の海洋への放射性物質放出は即座に地元の海洋生物への懸念となり、消費者たちが長期にわたって心配することとなった。日本政府は直ちに漁業を停止させ、領域のどの海産物が安全で、それらを食べても心配はないのかを判断するための徹底した検査とテストプログラムを開始した。
放射性物質は水中で溶解されるかもしくは微粒子状となって存在し海洋に放出されます。」フランス放射線防御・原子力安全研究所上級専門員のサビーン・シャーマソン氏は説明した。「どちらの形態でも海洋生物が取り込む可能性があります。」
汚染された環境に生息する魚類は、外皮を通して、もしくは餌や海水を摂取することで放射性物質を吸収するかもしれない。しかし、どのくらいの期間体内に残留するかは、元素固有である。セシウムは例えば元素周期表上で同じ列に属する、カリウムと似た働きをするため、筋肉や臓器に取り込まれ、海洋生物の体内に何週間も何ヶ月も残留する可能性がある。トリチウム、これは水素の放射性物質であり、主に水のように振る舞い、生物の体内機能からほんの数日で排出されてしまう。ストロンチウムはカルシウムに類似していると、シャーマソン氏は話した。そして、それは生物の骨内に何年も残存する可能性があるとも云う。
また、海洋生物にも固有である。タコはウニとは異なる放射性物質を吸収する。活発な代謝機能を持つ魚類は、汚染をより急速に除去できるかもしれない。
研究者たちは、福島周辺の海底近くに生息する生物に、海水の汚染濃度が下降し始めていたにもかかわらず、より高濃度の放射性物質を検知した。
「これは、これら魚類が汚染された堆積物上や内部の餌を摂取していたからです。」シャーマソン氏は説明する。
しかしながら、数年後には、日本の福島の漁場を含む東北沿岸で水揚げされた圧倒的多数の海産物は、１キログラムあたり１００ベクレル（アメリカ合衆国の制限値は１キログラムあたり１２００ベクレル）という日本の厳しい放射線量制限値を下回った。２０１５年以来、何千匹もの魚類が検査された中で、その制限値を超えたのはたった二匹のみであった。
福島第一原発の事故後、誤った情報が拡散し、科学者や政府関係者の情報へ対する世間の不信感が高まった。一般的に誤って伝わったもののひとつの例として、福島第一原発でメルトダウンした直後の放射性物質の広がりを示した地図と思われたものは、実際には地震後に太平洋を横断する津波モデルの分布図であった。 （米国海洋大気庁太平洋海洋環境研究所より転載）
安全が実証されたにもかかわらず、福島県地方から流通する海産物には汚染という汚名が今もつきまとう。２０１３年から２０１７年まで駐日アメリカ合衆国大使を務めたキャロライン・ケネディ前大使は、地域を訪問し地元産のものを食べることが安全であると人々に示すため、繰り返し現地を訪れたことを思いおこした。
「漁業に携わる人々や大勢の生産者に会いましたが、当然のことながら多くの場合、皆が彼らの食品や魚を購入することを恐れています。」ケネディ前大使は語った。「これら全てのエピソードはバラバラのようにみえますが、災害対応のための様々な分野に対して、個人そして集団としての責任、さらには科学のために、多くの教訓を与えてくれます。」
放射性物質は土地や海洋上でどのように分布しているのか？避難が必要なのは誰か？どの食べ物が安全なのか？人々がこうした当たり前の疑問であるはずのものに答えを希求してやまない時、福島についての信頼性を欠いた情報が災害後何日も何週間もかけて広まっていった。
しかし、日本政府から発信された情報は乱雑で、遅延し、不透明であったのみならず、不完全なものだったと、福島原発事故を受け組織された環境監視団体であるセーフキャストの主任研究員アズビー・ブラウン氏は話した。東京周辺地域の放射線汚染を示す最初の公式マップは、災害から７ヶ月も経過した２０１１年１０月になるまで発表されなかった。風評と誤報が混乱とともに、どのような公式発表よりも急速により遠方へ広がっていった。
「信頼は、再生可能なものではありません。」ブラウン氏は云う。「一度失ったら、二度と取り戻せないかもしれません。」
福島原発事故以前、日本における魚類の放射性物質濃度の制限値は１キログラムあたり５００ベクレルと、すでに国際的基準よりも厳しいものであった。２０１２年４月、福島産海産物の安全性への国民の信頼を高めるために、制限値は１キログラムあたり１００ベクレルに引き下げられた。しかし、この改正を取り巻く明確な情報の欠如が、多くの人々にさらなる混乱と不安をもたらした。以前は安全ではない海産物を食べてきたのか？と。
「誰のための情報なのか、その情報に対しどう反応するのか、いかにしてその情報を得るのか、もしそうしたことを想定しなければ、その情報は的外れになる可能性があります。」ブラウン氏は話す。「我々は情報発信の際、想定される混乱と、とどのように物事は誤解され得るのかを、予測しなければなりません。」
震災後の早い時期にすでに多くの国民が公式の情報源への信用を失い、続く不手際や同様に幾つかの情報の不正確さが問題をさらに深刻化させ、福島原発事故を取り巻く全てに信頼の危機が生まれた。
2011年3月11日に始まった終わりない惨劇の遺物、それは福島第一原子力発電所の敷地内に設置された千基以上の汚染された処理水を保存する貯蔵タンクである。日本政府はこれらのタンク内の汚染水を徐々に海洋に放出する予定である。厳密にはその処理水の中にどの放射性同位体がどの程度含まれているのか、明確にされていない。（撮影：ケン・ベッセラー、©ウッズホール海洋研究所）
東北の景観を変えただけでなく、震災は日本人の意識を根本的に変えた。震災の余波で、日本にはボランティア活動とフィランソロピーの感覚が戻った（新しく芽生えたと一部の人は云うだろう）。フィッシュ・ファミリー財団理事で、日本女性リーダー育成支援事業の共同創設者でもあるフィッシュ東光厚子氏は、地震と津波発生からわずか３週間後に手助けと彼女が在住するボストンで自ら募った基金を配布するため東北を訪れた。日本社会は伝統的に国外からの援助やもしくは別居する家族からであっても、外部の助けに抵抗する気風がある。そのためフィッシュ氏は人々が彼女を信頼することでしか援助を受けいれてもらえないと理解していた。彼女の動機が心から援助したいと望んでのことであると証明するためであれば、何ヶ月もかけて、時には被災地まで運送トラックに便乗させてもらうなど、根気強くボストンと東北を行き来した。
フィッシュ氏とそしてその他多くの人々の努力は、「信頼に基づくフィランソロフィー」とによって実ったと彼女は言う。特に信頼関係を築くことに重点をおいた支援の提供を担う女性たちの役割には、日本における女性たちの権利に、新たな推進力をもたらす強い影響を与えたと、彼女は指摘する。
「これら女性たちは、東北の将来を担うでしょう。」フィッシュ氏は語る。「同時に、彼女たちは日本にとって重要な将来のリーダーになる存在です。」そして、まだ成し遂げなければならないことがあり、彼女たちのリーダーシップが必要とされるはずである、と。
現在、福島第一原発敷地内には、千基以上の貯蔵タンクがそびえ立ちひしめきあっている。それらには汚染地下水と原子炉心や炉心内の瓦礫に接触した汚染冷却水が溜められている。目下のところ、1日１００トン以上の割合で排出、蓄積され続けている。当初は一時的なものと考えられていたが、１０年前に始まったことは長期化する可能性のある事象の遺物として、一つのより目立つ存在となってきた。原発を所有する東京電力ホールディング株式会社（TEPCO)によれば、２０２２年までに貯蔵タンクのためのスペースが、確保できなくなるとみられている。貯水したものは除染を経たうえで、現状のプランでは徐々に海洋に放出する計画である。
しかし、除染処理は完全ではなく、東京電力と日本政府の不透明性は計画への大衆の反発を招いた、とブラウン氏は語った。東京電力は何年もトリチウムのみがタンクに残存していると主張し、水素の放射性物質は取り除くのが困難ではあるが、他の放射性同位体に比べ健康へのリスクは低いという立場を取っている。２０１８年１０月にようやく、同社は貯蔵タンクには他の放射性同位体が含まれていると認めた。
それら他の放射性同位体というものが、人間の健康により危険であると、ベッセラー博士は云う。そして海底に残存して海洋生物に蓄積する可能性が高いとも。「少しでも透明性があれば我々の理解を得るのに長い時間はかからなかったでしょう。そしてトリチウムだけでなく他の同位体も含めた解決策を構築させたでしょう。」
最初のステップはタンクの中身を完全に把握することである。そして、ベッセラー博士は続ける。東京電力はトリチウム以外の放射性同位体を除去できることを証明しなければならない。東京電力は全タンクの70％以上にその除染処理が必要であると認めている。最後に、再処理後に各放射性同位体が許可された許容可能な数値内に抑えられているかを徹底的に調査する独立した監視が必要となる。ベッセラー博士は、短命な汚染物質の一部が減衰するのを受け入れるため、原発の周囲１９キロメートル弱の立ち入り禁止区域を設け、さらにタンクを設置する可能性も示唆している。しかし、再度巨大な地震に見舞われれば、タンクを破損し、制御不可能な漏出を起こす可能性が懸念される。
どのような解決策であれ、完全な廃炉と汚染除去は何十年もの長期事業になるだろう。そして、海洋生態系の回復と地域社会の復興が続く中、「安全なのか？」という疑問は多分これからも決して消え失せることはないと、ベッセラー博士は認知している。
「数値が下がったとしても、世間はなおそうした疑問を持つでしょう。」ベッセラー博士は云う。「そして次の１０年後も、我々がその疑問の答えを見つけようとしていることを願っています。」
＝（ローラ・カスタニヨン) biology Coastal Ecosystems Ocean Life
Fukushima Dai-ichi and the Ocean:
A decade of disaster response
By Laura Castañon
On the high seas
Observers join Orpheus cruise thanks to the Neil Armstrong Fund
By Hannah Piecuch
On March 11, 2011, a magnitude 9 earthquake 80 miles east of the Japanese city of Sendai generated a towering tsunami that slammed into the coastline and critically damaged the Fukushima Dai-ichi nuclear power plant. Nearly 16,000 people died and the releases of radioactive water from the plant continue today. (Photo by Ken Kostel, © Woods Hole Oceanographic Institution)
On March 11, 2011, 80 miles east of the Japanese city of Sendai, the seafloor heaved. The tectonic plate that holds Japan, which had been slowly compressed by the Pacific plate diving underneath it, suddenly slipped and sprang back. In a matter of moments, parts of the ocean floor were shoved as much as half a football field horizontally and 30 feet upwards.
Japan experiences hundreds of earthquakes every year, but the Great Tohoku Earthquake was the most powerful the country had ever recorded. The 9.0-magnitude quake lasted as long as six minutes and shifted the main island eight feet to the east.
Tsunami waves, generated as the seafloor thrust upwards, hit the closest parts of the Japanese coastline less than half an hour later. Entire towns were destroyed by the three-story wall of water and nearly 16,000 people were killed.
The Fukushima Dai-ichi nuclear power plant had also been damaged. In the following days, explosions rocked the facility and more than 150,000 people were forced to evacuate the surrounding area to avoid potential radioactive fallout. Even more radioactivity was washed into the ocean or deposited there from the atmosphere.
“Fukushima Dai-ichi was an unprecedented event for the ocean, in terms of the amount of radioactivity going in to the ocean from a disaster of this nature,” said Ken Buesseler, a senior scientist at the Woods Hole Oceanographic Institution. “It seems very important to look back and take stock of where we’re at.”
A decade after Japan’s triple disaster, Buesseler joined researchers around the world for a remote discussion of the events at Fukushima, what they’ve learned over the past decade, and how the situation continues to evolve.
Inside the power plant
The Fukushima Dai-ichi nuclear plant had systems in place to cope with an earthquake. When the violent shaking damaged utility lines and cut off the plant and its six reactors from the power grid, the three active reactors shut down automatically. But shutting off a nuclear reactor isn’t as simple as turning off the lights.
“Even if the fission reaction stops, the radioactive material continues to generate heat,” said Jota Kanda, a professor at Tokyo University of Marine Science and Technology who has led several research expeditions off the coast of Fukushima. “You have to keep cooling by water for quite a long period.”
The facility switched over to its backup generators to continue pumping the water needed to cool the fuel rods. Then the tsunami hit.
The nuclear plant was constructed on a cliff which had been excavated down to 30 feet above the ocean. The maximum expected height of a tsunami in that area was around 20 feet, Kanda said. But the tsunami waves that hit that day measured between 37 and 50 feet high. They flooded the facility and destroyed the backup generators.
When the cooling systems failed, the temperatures in the reactor cores began to rise. The fuel rods inside the reactors started to overheat and melt, exposing the uranium fuel and damaging their containment vessels. At the same time, water in the reactors turned to steam and began reacting with the metal fuel rods, generating volatile hydrogen gas.
To relieve the pressure building up in the reactor cores, plant workers vented the gas several times over the next few days. This gas carried radioactive isotopes, also known as radionuclides, into the atmosphere, but this was not enough. Over following days, three hydrogen explosions at the plant sent even more radioactivity skyward, much of it eventually settling in the ocean.
Emergency crews desperately sprayed the overheating reactors with water cannons and firehoses, and military helicopters dropped hundreds of gallons of water from above. This water also picked up radionuclides and overflowed into the ocean or seeped into the ground, carrying those isotopes to the ocean.
The earthquake knocked out power at Fukushima Dai-ichi and the tsunami flooded back-up generators, causing three of the six reactors to overheat and generating hydrogen gas that later exploded. Irradiated groundwater and cooling water flowed into the ocean, some collecting in beach sands and seafloor sediment, some building up in fish and other organisms, and the rest spreading with currents across the Pacific. (Fukushima Central Television)
The first international research expedition in June 2011 traced the spread of radionuclides from the coast near Fukushima Dai-ichi to more than 300 miles offshore. Over the past decade, scientists, technicians, and members of the public have collected samples of water, sediment, and marine life from the ocean near the power plant to the West Coast of Canada and the U.S. (Photo by Ken Kostel, © Woods Hole Oceanographic Institution)
A radioactive ocean
Some of the most abundant radionuclides released in the disaster were iodine-131, cesium-134 and cesium-137. All are potentially hazardous, but they decay at different rates. Most of the iodine-131 was gone in a matter of weeks. With a two-year half-life, only 3% of the cesium-134 remains after 10 years, making it a telltale, but rapidly diminishing, fingerprint of Fukushima’s impact on the ocean. The cesium-137, which has a half-life of 30 years, will linger for decades. In fact, there is still a small but measurable amount of cesium-137 in oceans around the world from atmospheric nuclear weapons testing in the 1950s and ’60s.
“Since the dawn of the nuclear era, we’ve always have some cesium; the question is how much more did this accident add,” said Buesseler, who led a research trip to measure radiation near Fukushima in June 2011. “We saw extremely high levels-more than 50 million Becquerels per cubic meter-of this radioactive form of cesium in the ocean close to Fukushima Dai-ichi.”
One Becquerel is a very small amount of radioactivity-it equates to one atomic nucleus decaying per second. The World Health Organization guidelines suggest that drinking water shouldn’t contain more than 10,000 Becquerels per cubic meter of cesium-137. Prior to the disaster, the waters around Fukushima had about 2 Becquerels per cubic meter. That shot up to over 50,000,000 immediately after the accident, then quickly dropped in the months following as measures to stanch the flow of radionuclides from the plant were put into the effect. Some of the radioactivity accumulated in the seafloor sediments, but much of it was dispersed into the Pacific by the strong Kuroshio Current, sparking fears that ocean currents would carry cesium to North America.
To investigate the movement of Fukushima radionuclides across the Pacific, Buesseler organized a community-based effort to determine what the levels of cesium were on the West Coast. His lab received seawater samples from ships operating in the area, and from surfers and beachgoers up and down the coast. While they did find evidence that some of the radioactivity from Fukushima had been carried across the Pacific to North America, the levels were extremely low-less than 10 Becquerels per cubic meter.
“That’s a very small number,” Buesseler said. “If you swam in the ocean every day for a year in waters that were about 10 Becquerels per cubic meter, the dose, the additional exposure, would be about a thousand times less than a single dental X-ray. The risk isn’t zero, but it’s so small that I wouldn’t be concerned about swimming, surfing or boating off the West Coast.”
The radioactivity at Fukushima has not entirely dispersed, however. Leaks from the reactors, radioactive sediment in rivers, and contaminated groundwater continue to flow into the ocean, albeit in much smaller amounts than in the first few years after the disaster. Levels in the coastal waters near Fukushima have stayed around 100 Becquerels per cubic meter since 2016.
What about the fish?
The abrupt flood of radioactivity into the ocean was an immediate concern for local marine life, and a long-term concern for the people who consume it. The Japanese government immediately shut down fisheries and began an extensive monitoring and testing program to determine what seafood from the region, if any, would be safe to eat.
“Radionuclides that have been released into the ocean can be in either dissolved or particulate form,” said Sabine Charmasson, senior expert at the Institute for Radiological Protection and Nuclear Safety in France. “Both can be taken up by marine organisms.”
A fish living in a contaminated environment might absorb radionuclides through its skin or ingest them with its food or water, but how long they remain depends on the specific element. Cesium, for example, acts like its cousin on the periodic table, potassium, and is taken up by muscles and organs, where it can remain in the animal for weeks or months. Tritium, a radioactive form of hydrogen, behaves primarily like water and can be flushed out of an animal’s system in a matter of days. Strontium is more akin to calcium, Charmasson said, and can linger in a creature’s bones for years.
The particular animal species in question matters as well. An octopus will take up certain radionuclides differently than a sea urchin. A fish with a speedy metabolism might clear contamination more quickly.
Researchers found that animals living near the seafloor around Fukushima had higher levels of radioactivity, even as the contamination levels in the water began to fall.
“This is because these fish feed on prey living on or inside contaminated sediment,” Charmasson said.
After a few years, however, the vast majority of seafood caught off the Northeast Coast of Japan, including the fisheries off Fukushima, was below Japan’s strict radiation limit of 100 Becquerels per kilogram. (The U.S. limit is 1200 becquerels per kilogram.) Since 2015, out of thousands of fish that were tested, only two have exceeded that level.
In the wake of the accidents at Fukushima Dai-ichi the spread of misinformation inflamed public distrust of information from scientists and government officials. One commonly shared fallacy was a map, supposedly showing the spread of radiation immediately after the meltdowns at Fukushima Dai-ichi, but that was actually a model of tsunami waves crossing the Pacific after the earthquake. (Image courtesy of NOAA Pacific Marine Environmental Lab)
A crisis of trust
Despite being demonstrably safe, the seafood from the Fukushima region still carries a stigma of contamination. Caroline Kennedy, who served as the U.S. ambassador to Japan from 2013 to 2017, recalled traveling to the region repeatedly to show that it was safe to visit and eat the local foods.
“You meet these people who are fishing and trying to grow food but everybody is scared to buy their food or their fish, understandably so in many cases,” Kennedy said. “This whole episode is something that, as we piece apart, has many lessons for different areas of disaster response, as well as personal and collective responsibility and science.”
Mistrust of information about Fukushima built in the days and weeks after the disaster, when people were desperate for answers to what seemed like simple questions: Where was the radioactivity traveling on land and in the ocean? Who needed to evacuate? What food was safe?
But communication from the government was messy, delayed, unclear, and incomplete said Azby Brown, lead researcher for Safecast, an environmental monitoring group formed in response to Fukushima. The first official map showing radiation contamination in the Tokyo area wasn’t released until October 2011, seven months after the disaster. Rumors and disinformation spread faster and farther than any official communication, adding to the confusion.
“Trust is not a renewable resource,” Brown said. “Once you lose it, you may never get it back.”
Before the Fukushima disaster, the Japanese limit for radioactivity in fish was 500 Becquerels per kilogram, already stricter than the international standard. In April 2012, in an in an attempt to build public confidence in the safety of Fukushima seafood, the limit was lowered to 100 Becquerels per kilogram. But the lack of clear communication around this change created more confusion and anxiety for many people. Had they previously been eating seafood that was unsafe?
“If you don’t think about who it’s for, how they’re likely to react, how they’re going to find this information, then the information may miss the target,” Brown said. “We have to anticipate the potential failure points and how things can be misunderstood.”
Many people lost faith in official sources of information early on in the disaster and continued missteps, as well as misrepresentation of some information, have compounded the problem, creating a crisis of trust around Fukushima.
One of the enduring legacies of events that began on March 11, 2011, is the more than 1,000 storage tanks on the grounds of the Fukushima Dai-ichi nuclear power plant holding contaminated wastewater that the Japanese government wants to empty into the ocean. Exactly what that water is contaminated with remains unclear. (Photo by Ken Buesseler, © Woods Hole Oceanographic Institution)
Fukushima’s ongoing legacy
In addition to changing the landscape of Tohoku, the disaster fundamentally changed the attitudes of of the Japanese people. In the aftermath, there was a renewed (some would say a new) sense of volunteerism and philanthropy in Japan. Atsuko Toko Fish, trustee of the Fish Family Foundation and co-founder of the Japanese Women’s Leadership Initiative, went to Tohoku just three weeks after the earthquake and tsunami to lend a hand and to distribute funds that she’d helped raise from her home in Boston. Japanese society has traditionally been resistant to outside help, whether it came from outside the country or even outside one’s family, so she knew that her help would only be accepted if the people trusted her. She spent months traveling back and forth between Boston and Tohoku, sometimes hitching rides on cargo trucks to get to the disaster-struck region-anything to prove that her motivations came from a sincere desire to help.
Her efforts, and those of many others, form the basis of something Fish calls “trust-based philanthropy.” In particular, she points to the role women have played in providing aid by focusing on building trust, which has had the added impact of giving new momentum to women’s rights in Japan.
“These women will shoulder the future of Tohoku,” said Fish. “They will be important future leaders of Japan, as well.” And their leadership will be needed, as there is still work to be done.
Today, the Fukushima Dai-ichi site is crowded with more than 1,000 towering storage tanks. They are filled with contaminated groundwater and cooling water that came into contact with the radioactive cores and debris. Currently, the wastewater is accumulating at a rate of more than 100 tons each day. The tanks were originally intended to be temporary, but they have become one of the more visible, and potentially long-lasting legacies of events that began ten years ago. The site will run out of space to store water by 2022, according to the Tokyo Electric Power Company (TEPCO), which owns the plant. The stored water has undergone a decontamination process, and the current plan is to slowly release it into the ocean.
But the decontamination process is not perfect, and a lack of transparency from TEPCO and the government has caused a public backlash against the plan, Brown said. TEPCO insisted for years that there was only tritium left in the tanks, a radioactive form of hydrogen that is difficult to remove but poses a lower health risk than other radionuclides. Only in October 2018 did the company finally admit that the water still contained additional contaminants.
These other radionuclides are more dangerous to human health, Buesseler said, and are more likely to remain on the seafloor and accumulate in marine life. “A little transparency would have gone a long way to make us accept and build a solution around not just tritium, but the other isotopes.”
The first step is to get a full accounting of what is in the tanks. Then, says Buesseler, TEPCO needs to demonstrate that they can remove the additional radionuclides, which they admit is needed for more than 70 percent of the tanks. Finally, independent monitoring of the ocean is needed to ensure that they only release what is permitted and at allowable rates. Buesseler also raised the possibility of building more tanks in the surrounding area-there is a 12-mile exclusion zone around the plant-to allow some of the shorter-lived contaminants to decay. But there are concerns that another large earthquake could fracture the tanks and cause uncontrolled leaks.
Whatever the solution, fully decommissioning and decontaminating the site will be a decades-long project. And as the marine ecosystem rebounds and communities in the area continue to rebuild, Buesseler knows the question of “is it safe?” will probably never go away.
“Even as levels get lower, the public will still have these questions,” Buesseler said. “And what I hope in ten years is that we’re still trying to give them answers.”
Finding answers in the ocean
In times of uncertainty, the deep sea provides potential solutions
By Elise Hugus | November 9, 2020
Deep-sea hydrothermal vents harbor diverse microbes whose enzymes can be used in diagnostic tests, like the ones to detect the novel coronavirus and other pandemics like AIDS and SARS. (Video acquired from the submersible Alvin at the East Pacific Rise near 9° 50’N at 2510 meters depth. © WHOI-NDSF, Alvin Group, National Science Foundation)
Deep-sea hydrothermal vents harbor diverse microbes whose enzymes can be used in diagnostic tests, like the ones to detect the novel coronavirus and other pandemics like AIDS and SARS. (Video courtesy of Chris German, WHOI/NSF/ROV Jason/2012/© Woods Hole Oceanographic Institution)
The test being used to diagnose the novel coronavirus—and other pandemics like AIDS and SARS—was developed with the help of an enzyme isolated from a microbe found in marine hydrothermal vents as well as freshwater hot springs.
Biomedical breakthroughs sometimes happen in the most unlikely places. Take the deep ocean, for example, where mineral-laden fluid superheated by magma gushes from hydrothermal vents. Under extreme pressure and acidity, at times with no oxygen to speak of, microbes not only survive there, they thrive. This incredible adaptation offers insight into how life evolved billions of years ago—and how modern humans may be able to fight infections and disease.
“We’ve found marine microorganisms that produce antimicrobials—basically chemical weapons that help them fight off other organisms, and molecular mechanisms that help them resist viruses,” says Virginia (Ginny) Edgcomb, a WHOI microbiologist who investigates fungi and bacteria living in the deep sea and deep subsurface biosphere. These microbes feed on tough compounds like hydrocarbons and produce antimicrobial compounds. “Almost every antibiotic we have was produced by microorganisms. Who knows—maybe we’ll find new antimicrobials when we start to look in deep ocean habitats.”
The deep ocean has already given us compounds to treat cancer, inflammation, and nerve damage. But breakthroughs have also come from the ocean depths in the form of diagnostic tools. Case in point: the test being used to diagnose the novel coronavirus—and other pandemics like AIDS and SARS—was developed with the help of an enzyme isolated from a microbe found in marine hydrothermal vents as well as freshwater hot springs.
The pathway to developing this test started back in 1969 when scientists discovered a bacterium, Thermus aquaticus, living in the extreme temperatures of a hot spring in Yellowstone National Park. Two decades later, WHOI biologist Carl Wirsen and colleagues discovered new strains of bacteria on a hydrothermal vent off of Italy that could withstand even greater extremes (including heat, pressure, and lack of oxygen). More heat-loving microbes have since been found in hydrothermal vent communities across the globe to depths as great as 5000 meters beneath the sea surface.
By the mid-1980s, the unassuming microbes had enabled a major advance in the emerging field of genetics. Scientists found that their enzymes remained stable, even at the temperatures required to perform a revolutionary procedure known as polymerase chain reaction (PCR). With enzymes recovered from the microbes, it became possible to make millions of copies of a single DNA sequence in just a few hours, essentially upgrading geneticists’ tools from carbon-copy paper to state-of-the-art Xerox machinery. A technique using these enzymes, termed DNA polymerases, as well as enzymes isolated from viruses, now make it possible to quickly test for viruses, including coronaviruses like SARS (avian flu) and COVID-19.
Identifying microbial processes in the deep ocean is an essential first step for discerning human applications, says WHOI microbiologist Julie Huber.
“A lot of people think of the deep sea as a desert,” she says. “To our naked eye, it looks like there’s nothing there. But hydrothermal vents have a remarkable diversity of microbes, including genetic diversity. There’s huge potential there. What I can do as a basic science researcher is describe them and make their genome available. And folks in applied science can take that data and turn it into something useful.”
Edgcomb says the coronavirus outbreak underscores the importance of funding basic exploratory research, which may help lead to a cure or diagnostic tool in the future.
“You need to have people exploring different habitats in order to continue feeding the pipeline of medically-relevant enzymes (proteins),” she says. “This is a tough lesson to learn, with this pandemic, but I do hope people realize that the more we can learn more about microbes, the better off we are.”
biology Hydrothermal Vents Ocean Chemistry
WHOI establishes new fund to accelerate microplastics innovation
By Hannah Piecuch | October 26, 2020
Confetti-sized bits of microplastic get swept through the ocean by fast-moving currents and shifting circulation patterns. (Photo by Shutterstock)
Despite regular media coverage and international concern over microplastics in the ocean, funding to study this emerging ocean pollutant has been surprisingly scarce. Early microplastics research by WHOI scientists was mostly funded through small grants that allowed them to explore very limited facets of the issue.
In 2017 and 2018, WHOI awarded Catalyst Funds—an incubator program funded by private donations—to form the Marine Microplastics Initiative. Leveraging WHOI’s interdisciplinary scientific staff, the initiative’s first priorities were taking stock of the existing research and coordinating a workshop to bring international experts together to chart a course forward. Now, the group has turned its attention to some of the most pressing—and foundational—questions about microplastics: How long do they last in the environment? Where do plastics discharged from wastewater systems end up? And what kinds of health risks do these plastics pose to animals and humans? They are also developing tools to sense and measure microplastics in the water and working on ambitious new projects related to the recovery and processing of plastic waste in the ocean. With the backing of a handful of family foundations, WHOI is launching a Marine Microplastics Innovation Accelerator to help drive innovation and support projects that will have the most impact.Hannes Frey, a director at March Limited, says the company chose to fund WHOI’s microplastics research in order to help close knowledge gaps that stand in the way of a healthier ocean and to inspire others to make similar philanthropic investments. “As we talked to scientists, we realized that the breakdown into microplastics and their entry into the food chain is one of the most challenging issues to understand. It’s not as visible as animals trapped in fishnets or a seashore covered with plastic bags, but I think that on a scientific basis, it is crucial.” The Seaver Institute is another organization that is helping fund microplastics research at WHOI. “We give seed money for research and support projects that other people aren’t willing to fund until they become understandable,” says the foundation’s president, Victoria Dean. “We are interested in the discovery of scientific fundamentals and getting the information out there—WHOI does a great job of sharing their work.” Funding from private foundations has been an indispensable part of moving this research forward, says Mark Hahn, principal investigator of the Microplastics Initiative. “Currently, there are many more questions than answers about the fate and impacts of microplastics in the ocean,” he says. “The growing support from private foundations is critical in enabling the interdisciplinary, cutting-edge research that is needed to understand and solve this global problem.”
Putting the ‘nuclear coffin’ in perspective
Marine chemist weighs in on leaking radioactive dome in the Pacific
By Evan Lubofsky | August 13, 2019
WHOI geochemist Ken Buesseler discusses marine radioactivity monitoring in the Marshall Islands atop Runit Dome—a 350-foot-wide concrete lid built to contain contaminated material from nuclear weapons tests. (Photo courtesy of Ken Buesseler, Woods Hole Oceanographic Institution)
There has been a flurry of headlines this summer about a “nuclear coffin” leaking radioactive waste into the Pacific Ocean. The coffin—a bomb crater filled with radioactive soil on a tiny island in the Marshall Islands—sits under a 350-foot-wide concrete lid known as Runit Dome. It’s arguably the region’s most visible scar from a series of U.S. nuclear weapons tests that took place off Bikini and Enewetak Atolls between 1946 and 1958.
The concerns aren’t unfounded—the area has been a hotspot for lingering radioactivity for more than half a century. But according to Ken Buesseler, a world-renowned expert in marine radioactivity at Woods Hole Oceanographic Institution (WHOI), the concerns are nothing new.
“We’ve known for years that the dome is leaking,” he said. “When we were there doing fieldwork in 2015, we sampled groundwater and could see there was an exchange between the lagoon water and material under the dome. But it was clear that only a small amount of radioactivity was actually leaking into the lagoon.”
To put “a small amount of radioactivity” into perspective, Buesseler says the amount of plutonium under the dome is just one percent of the total amount buried in the surrounding lagoon sediments, which is less than 0.1% of the plutonium released during the weapons testing more than 60 years ago. These amounts fall below contamination levels for U.S. and international water-quality standards. More generally, radiation levels for the islands of Enewetak Atoll, according to a 2016 study from researchers at Columbia University, are even lower than those in New York City’s Central Park due to the high background radioactivity of granite rocks in the park.
“The dome is a significant visible scar on the landscape, but it’s a relatively small source of radioactivity,” said Buesseler, who had no hesitancy swimming in the azure waters off Runit Island during the 2015 field study.
However, he says the area is generally still of great concern and needs to be closely monitored. A more recent study from Columbia suggests that radiation levels vary significantly between islands, and higher levels have been measured on nearby Bikini and Rongelap atolls. Rongelap, in particular, had received considerable fallout from the 1954 Bravo test, resulting in subsequent decades of local contamination and radiation poisoning throughout the atoll.
Runit Dome sits roughly 25 feet above sea level on low-lying Runit Island, making it vulnerable to inundation from rising seas. People on top of the thick concrete cap, which measures nearly 400 feet in diameter, look like ants in this aerial view. (Photo from Wikimedia Commons)
Runit Dome, which is located on Runit Island—one of 40 islands that make up Enewetak Atoll—was built in 1977 as a temporary measure to contain some of the radioactive material left behind from the bomb explosions, some of which were one thousand times more powerful than those that destroyed Hiroshima and Nagasaki. The U.S. Army bulldozed more than 100,000 cubic yards of contaminated soil and debris into a bomb crater and capped it with hundreds of 18-inch-thick concrete slabs. From a Google Earth perspective, the massive dome looks like something out of science fiction, and completely out of place against the expanse of paradise around it.
While the dome has helped contain the waste and residual contamination levels on Enewetak, there’s no telling what the future holds.
“As long as the plutonium stays put under the dome, it won’t be a large new source of radiation to the Pacific Ocean,” he said. “But a lot depends on future sea-level rise and how things like storms and seasonal high tides affect the flow of water in and out of the dome. It’s a small source right now, but we need to monitor it more regularly to understand what’s happening, and get the data directly to the affected communities in the region.”
Runit Dome, which is located on Runit Island—one of 40 islands that make up Enewetak Atoll—was built in 1977. It was an attempt to contain some of the radioactive material left behind from nuclear testing during which more than 30 megatons of TNT was detonated. The U.S. Army troops bulldozed more than 100,000 cubic yards of contaminated soil and debris into a bomb crater and capped it with hundreds of 18-inch-thick concrete slabs. From a Google Earth perspective, the massive dome looks like something out of science fiction—and completely out of place against the expanse of paradise around it.
The military never returned to the islands to remove the waste—and it’s hard to say where they would have put it if they had. But it turns out, the dome may end up being a temporary container for the contamination after all: rising sea levels have caught up with it.
“The dome is only about 25 feet above sea level to begin with,” Buesseler said. “And sea levels are now at the point where seawater has been washing up on the dome and eroding its concrete edges.”
He says there has been some patching of the concrete, but it’s not a long-term solution. Increased seawater inundation over time will hasten the deterioration.
“They hadn’t considered sea level rise in the 1970s when they built this,” Buesseler said. “And at the current rate, the whole dome will be at least partially submerged by the end of this century.”
That begs the obvious question of what higher seas will mean for additional radiation flow into the Pacific. Buesseler says it’s impossible to predict, but ongoing monitoring of the situation will be critical.
“As long as the plutonium stays put under the dome, it won’t be a large new source of radiation to the Pacific Ocean,” he said. “But a lot depends on future sea-level rise and how things like storms and seasonal high tides affect the flow of water in and out of the dome. It’s a small source right now, but we need to monitor it more regularly to understand what’s happening, and get the data directly to the affected communities in the region so the people there have more confidence in what their levels of exposure are.”
MC&G Department Radiation Health Risks Café Thorium
How do you measure a chemical in the ocean that exists for less than a minute?
This was the conundrum facing Colleen Hansel, a scientist at the Woods Hole Oceanographic Institution (WHOI). She studies superoxide, a molecule so unstable that it reacts almost instantly with other molecules around it, vanishing in about 30 seconds.
Bringing water back to the lab simply didn’t work. Any superoxide in it would be gone long before the water could be tested. For years, scientists had measured superoxide in experiments using pumps and a benchtop instrument in the lab designed for the task. However, that device was not built to be used in the field. Superoxide had never been directly measured in the ocean.
Superoxide molecules are an accidental byproduct of breathing. They are ubiquitous and highly toxic. Any living organism that breathes oxygen creates them, and then needs to dispose of them quickly.
To create energy, cells extract electrons from fats and carbohydrates and transfer them to oxygen. When an oxygen molecule grabs four electrons, it then combines with hydrogen to form water.
But this process can be sloppy, particularly when organisms are stressed. Sometimes, oxygen only takes one electron. This makes superoxide. The extra, unpaired electron makes superoxide highly reactive. It either wants to lose or gain another electron to become more stable. To do that, superoxide gives or takes electrons from other cells, setting off destructive chain reactions.
Superoxide has been linked to harmful impacts ranging from cancer to premature aging in humans. Ocean scientists also suspect that superoxide might be involved in coral bleaching—the phenomenon that occurs when the symbiotic algae that live inside corals (giving them food and their vibrant colors) suddenly depart, leaving corals pale and vulnerable to starvation, disease, and ultimately death.
But a link between superoxide and coral bleaching has only been indirectly inferred from studies in the lab.
“It’s difficult to directly measure superoxide in the ocean,” Hansel said. “We were discouraged by the fact that we couldn’t make any measurements in the field.”
Expensive equipment in a very small boat
If Hansel couldn’t bring the samples to the lab, then she had to bring her lab to the samples.
“We said, ‘Let’s just take this lab benchtop instrument out onto a small zodiac on a local pond to see if we can make measurements and hope that we don’t tip the boat over,’” Hansel said.
In 2012, she and a postdoctoral scientist in her lab at WHOI brought their lab instrument out onto Oyster Pond, a large, brackish pond on Cape Cod. They knew bacteria in the water produced superoxide, but could they pump the water fast enough into the instrument on the boat to capture it before it reacted away? If the water pumped into the instrument too quickly, the sensor wouldn’t have enough time to make a measurement. If the water moved too slowly, the superoxide would be gone.
It was a complicated operation. They lowered a weighted tube into the water connected to a pump to draw samples up to the boat. As those waters fed into the sensor, a second pump pulled in a chemical from a separate bottle that specifically binds with superoxide. Once it was analyzed, the waste water was collected through a third tube, while the data was sent to a laptop via Bluetooth, where Hansel could see it in real time. The whole system was connected to portable lithium batteries—also balanced precariously in the zodiac.
And it worked. The setup was unwieldy, and if the tube went too deep, the superoxide would be gone before it made it to the instrument on the surface. But it worked: Hansel had proved it was possible to measure superoxide in situ outside the lab.
This presented an opportunity that Hansel and her WHOI colleague, Amy Apprill, had been waiting for. They now had a tool to measure superoxide around corals in the wild to explore its role in coral stress and bleaching. They finally got their chance in 2014 when widespread bleaching occurred in shallow corals in Hawaii.
Into the wild
The fall of 2014 was a bad time for coral in Hawaii. The weather was unusually warm and prevailing winds, which usually pushed cooling open-ocean water toward shore and over coral reefs, died down. Coastal water temperatures in Kaneohe Bay, on the western side of Oahu, rose into the high 80s. More than three quarters of the dominant corals on the Kaneohe reef had bleached.
The theory behind coral bleaching is that superoxide builds up inside corals in response to heat stress and causes them to eject the algae they rely on. But as Hansel and Apprill loaded their setup into a small rented boat, they weren’t planning to measure the superoxide inside the corals. They wanted to know whether the corals were producing superoxide outside their cells in the surrounding waters.
They had seen this behavior in corals growing in aquaria in the lab. But were they doing it in the wild as well?
“I had concerns that the approach wasn’t going to work,” Hansel said. “Were the corals making enough superoxide for us to measure it using the set-up on the boat?”
But when the first measurements started coming in, from a resilient coral species known as Porites compressa, they showed that the corals had high levels of superoxide surrounding their colonies. Hansel couldn’t contain her excitement.
Several more days of sampling began to reveal a pattern: Hardier coral species, the ones more likely to recover from coral bleaching or avoid infections, had more superoxide around their colonies. More fragile species had less, or none at all.
Clearly, there was more to the superoxide story. Perhaps superoxide could be beneficial to corals as well.
To see if these results were part of a larger pattern, Hansel would need to test other, deeper reefs. The reefs in Hawaii were shallow, allowing Hansel and her team to pump water to the instrument set-up in their boat before the superoxide vanished. She needed a better tool.
“After Hawaii, I knew that I wanted to make an in-situ instrument,” Hansel said.
DISCO designs
Back in Woods Hole, Hansel started brainstorming ideas with WHOI biogeochemist Scott Wankel. Wankel had experience building deep-sea sensing instruments for exploring hydrothermal vents on the seafloor. The two scientists have been married for 11 years.
“We sit around talking a lot, obviously,” said Wankel. “I remember sitting in the kitchen, taking a napkin, and drawing it. ‘What do you need? And how does it work? I have a pump that could do that …’ and putting this idea together.”
Together, over a year’s worth of Saturday morning coffees, they began to design what would become the DISCO: a portable, underwater, superoxide detector.
DISCO is short for DIver-operated Submersible Chemiluminescent sensOr (“We cheated on the acronym a little bit,” Wankel said.) It’s a device the size of a small suitcase, controlled by a handheld screen with five buttons and real-time read out display. It is a hefty 60 pounds in air, but neutrally buoyant in water and can operate to depths of 100 feet (30 meters).
The basic mechanics of the DISCO are similar to the lab instrument. Water is pulled inside through a long, thin wand and mixes with a chemical that reacts with superoxide in a mixing cell to produce light that is detected by a photomultiplier tube. The amount of light detected is translated through a small computer to show how much superoxide is in the water.
But this relatively straightforward reaction is made exponentially more complicated by superoxide’s tendency to react with any material it meets. “Superoxide is non-selective,” Hansel said. “It reacts with carbon, metals, other organisms. It reacts with nearly everything.”
The DISCO had to be built out of inert materials such as certain plastics, ceramics, or glass that superoxide can’t react with—nothing metal. These parts can be found, but they’re highly specialized and typically not made for underwater use.
Wankel reached out to WHOI engineer Jason Kapit, who he had worked with on several other projects. “Jason is a master of perusing the literature to find parts and pieces we can use,” Wankel said.
“You’re trying not to re-invent the wheel,” Kapit said. “Sometimes it takes cannibalizing a part that already exists and adapting it to what you want.”
Eventually he found parts from inert benchtop chemistry pumps to pull in seawater and intravenous bags from the medical industry to hold the necessary chemicals. These, along with a small computer, a lightproof chamber, and various other components were packed into a waterproof, pressure-bearing case.
Hansel had been invited to bring the DISCO on a joint U.S.-Cuban expedition to the Gardens of the Queen reefs in Cuba in October 2017. The expedition, led by Apprill, was aboard the research vessel Alucia. The group had hoped to finish the DISCO in time to test it locally, but design and construction took them longer than expected—into the fall of 2017.
“Right before we had to leave, we got it dunk-tested to confirm that it turned on underwater and didn’t leak,” Hansel said. “Cuba was the first field test.”
The trip to Cuba was an opportunity to see if coral species in a healthy Caribbean reef were producing superoxide like their stressed Hawaiian counterparts. That information could lead to a better understanding of the role of superoxide. But getting the data was entirely dependent on the unproven DISCO actually working.
A two-faced chemical?
Scott Wankel knew there were a lot of things that could go wrong.
“This was Colleen’s first project developing an instrument,” he said. “I kept warning her that the alpha prototype may never even make it to the water, let alone make a measurement, let alone make a measurement that is actually meaningful.”
Hansel wasn’t even going to be the one to first test the DISCO in the ocean. Her graduate student, Kalina Grabb, was joining the boat in Cuba two weeks before Hansel.
“It was nerve-wracking. We didn’t know what would happen,” Hansel said. “This was a lot of pressure for a first-year student, so I told her before she went, if you don’t feel comfortable, don’t do it. But she jumped in with it, and she got data on the first dive.”
It wasn’t entirely smooth sailing. The pumps ran too hot and caused the readout screen to overheat.
“After about 10 minutes of use under water, the screen would freeze,” Hansel said. “It took us a while to realize that DISCO was actually still collecting data, we just couldn’t see it.”
Flying blind, they collected data from a variety of coral species. When they were able to view it on the computers, it matched up with what they had previously seen in Hawaii and in the lab experiments.
“What we got from the DISCO is exactly what we got from the benchtop instrument that we schlepped onto the boat in Hawaii and the same that we got with the aquaria-based corals,” Hansel said. “Porites, a coral known for its resistance to stress, has extremely high concentrations of superoxide around itself, sometimes a hundred times higher than seawater.”
If the most resilient corals are producing the most superoxide, maybe superoxide isn’t all bad for corals. Perhaps the layer of superoxide on the outside of corals provides some kind of protection for stressed corals, like fending off viruses or bacteria that might otherwise infect them or helping with tissue repair. This would be similar to what scientists have observed in other forms of life, such as plants and fungi, and even mammalian cells.
“It’s exciting to think about,” Hansel said. “Is superoxide providing a physiological benefit to the coral?”
To answer this question, the team began working on a smaller, lighter version of the DISCO. Kapit took the lead on incorporating smaller, more efficient pumps to avoid overheating, a sleek touchscreen screen for the diver, and other improvements. He also eliminated machinery humming that emanated from the original DISCO, which attracted curious wildlife. Grabb field-tested the new DISCO in the Caribbean over six weeks in the summer of 2018.
The team is also working on a project called the SOLARIS (Submersible Oceanic Luminescent Analyzer of Reactive Intermediate Species), a superoxide detector that can be used at deeper depths and could be incorporated into a deep-sea sampling platform such as WHOI’s submersible, Alvin.
SOLARIS will allow the team to better understand superoxide’s role throughout the ocean. In addition to coral bleaching, superoxide has been implicated in harmful algal blooms and fish kills associated with red tides. But based on lab experiments, Hansel and colleagues have an emerging theory that superoxide is important, perhaps essential, for cell growth in bacteria and phytoplankton.
“Because superoxide is so reactive, it’s going to play a central role in nearly all biogeochemical cycles,” said Hansel. “Being able to finally measure superoxide directly within various marine ecosystems will transform our understanding of its role in ocean chemistry and health.”
This research was funded by Schmidt Marine Technology Partners and the National Science Foundation’s Division of Ocean Science.
An estimated eight million tons of plastics enter our oceans each year, yet only one percent can be seen floating at the surface. This is the first in a three-part article series about how researchers at Woods Hole Oceanographic Institution are trying to understand the fate of “hidden” microplastics and their impacts on marine life and human health.
When we think of plastic in the ocean, we often think of easily seen things such as water bottles and plastic bags. In reality, the vast majority of plastics in the ocean are smaller than a millimeter and can’t be seen with an unaided eye; some particles resemble bird seed, others look like dust.
These small fragments are known as microplastics. Some are “micro” by design: Microbeads, for example, are tiny plastic spheres manufacturers add to body washes, toothpastes and other products to give them extra scrubbing power. Lentil-sized pellets known as nurdles are ubiquitous fodder used in the manufacture of many common plastic products, are also intentionally small.
Other microplastics become “micro” over time when larger pieces of plastic debris, such as water bottles, straws, cups, and car fenders, are exposed to forces of nature that cause them to degrade. Sunlight, for example, oxidizes plastic and causes it to weather and degrade. Freeze-thaw cycles can weaken the structure of plastics over time. And ocean waves could also be taking a toll, making plastics more brittle by constantly washing over them and grinding them into sand.
Scientists have a decent sense for the types of physical and chemical weathering processes that can cause plastics to break down. However, little is known about how quickly degradation happens, and whether most of it is happening on land, in rivers, or in the ocean. It’s unclear, for example, what happens to a plastic water bottle between the time someone takes his or her last swig and when the empty bottle ends up in the ocean, said WHOI senior scientist Chris Reddy.
“There’s a perception that most of the fragmentation of plastics is happening in the ocean, but it could be that a lot of the activity is actually happening on land,” he said. “For example, if you take a red ‘Solo’ cup and leave it on the ground outside for a week, you can see that the red color starts to fade to pink and that the cup is more brittle. So, pre-aging on land could be playing a major, currently unaccounted for role in the fate of plastics in the ocean.”
Another big unknown is the impact marine microbes have on the breakdown of plastics in the ocean. Studies have demonstrated that microbes cling to even tiny plastic fragments, and nibble at them as well. But whether they are causing any significant breakdown of the material is something that scientists at WHOI are just starting to investigate.
The uncertainty surrounding where and how quickly plastics break down has become a critical knowledge gap not only for scientists, but also for chemical companies and plastic manufacturers that want to design plastics that decompose faster into materials that are non-harmful and have minimal effects on the environment.
One way to gauge the speed of degradation is by placing plastics—including “raw” plastics containing no additives, as well as consumer products such as Styrofoam cups—in specialized weathering chambers. Scientists can conduct experiments in these chambers that test how factors such as sunlight, temperature, and humidity contribute to physical breakdown processes.
“These chambers provide a realistic picture of what happens on land and in the ocean,” Reddy said.
Collin Ward, a marine chemist at WHOI, says one of the main advantages of the weathering chamber is speed: It can accelerate the weathering process to answer environmentally relevant questions faster. When testing the effects of sunlight, for example, the chamber’s light source can be cranked up to flood plastics with ultraviolet light that is ten times more intense than natural sunlight.
“Some of the longest experiments I’ve ever run have been on plastics, and the reaction times are very slow since plastics are designed to not break down easily,” he said. “With these chambers, we can easily get the equivalent of a month’s worth of sunlight in one week, so it really accelerates the weathering.”
Weathering chambers will help, but Ward says that gaining a true sense for how plastics breakdown will be far more complex than simply blasting them with sunlight in a box. This is due to the fact that there are so many different types of plastics, and each type may break down at different rates in the environment due to the base polymers used and the types of additives and pigments applied to the materials during the manufacturing process.
“Cellulose acetate is completely different from polystyrene and polyethylene,” he said, “so these products will weather at different rates and by different processes. And then you have plastics that come in various colors, each with their own pigments and additives that can initiate the fragmentation process at different rates. When you consider all the variables that can impact the breakdown process, it becomes an incredibly complex science question.”
For more information about WHOI’s Marine Microplastics Initiative, visit microplastics.whoi.edu.
My eyelids were tightly pressed down as I mustered all the tricks I could think of to get myself to sleep. I rolled around with no sign of getting close to slumber. I had no ticking bedside alarm clock to mark the passage of time. The only audible sound was the thunderous waves crashing against the side of the research vessel Atlantis.
Tonight was far from ordinary. Soon after sunrise, I would dive to the bottom of the Pacific Ocean in the submersible Alvin. I had learned about Alvin for the first time in a biological oceanography class I took in my sophomore year at Chulalongkorn University in Bangkok, Thailand. That seemed like a long time ago. Since then, I had become a graduate student in the MIT-WHOI Joint Program in Oceanography, and I had seen so many photos and videos of hot springs on the seafloor, spewing hot fluids like geysers into the deep ocean. But all of those were nothing compared with what I was about to witness with my own eyes.
My goal for this dive was to collect some samples of hot fluids venting from the seafloor 1.6 miles beneath the surface. I was looking for a particular chemical compound in the fluids: ammonia.
Many of you know ammonia as a common ingredient in cleaning products or fertilizers. But it is also scientifically intriguing, because it is the nitrogen-containing compound that can be converted most easily into key building blocks necessary for life: amino acids—the foundation for proteins and enzymes.
Ammonia is scarce in the ocean, but you can find it in large amounts at vents. Not only are vents oases of life in the deep sea today, they are also thought to be among the possible places where the first life forms on Earth emerged in the distant geologic past. My hope is to study the chemical fingerprints of the ammonia in vent fluids and unravel the chemical processes going on beneath the seafloor that produce it. If we can better understand the geochemical forces that produce ammonia today at vents, it will help open a window into what may have been happening in Earth’s ancient ocean to spark life.
Down to the abyss
Each Alvin dive requires an extraordinary amount of preparation. Many scientists studying various aspects of vents were aboard Atlantis, and Alvin was at the service of all of them. At a meeting the night before my dive, Stefan Sievert, a biologist at Woods Hole Oceanographic Institution and chief scientist of our expedition, went through the long list of tasks to accomplish during the dive. The pilot would execute those tasks, but it is imperative for the scientists inside Alvin to fully understand them, as they often have to make instantaneous judgment calls on how to proceed when questions and unanticipated circumstances arise—as they commonly do.
Now you probably understand why numerous thoughts were racing in my mind as I rehearsed every possible scenario that might happen on the dive and went through everything that needed to get done.
The next morning, full of adrenaline, I got into Alvin. The descent to the seafloor took a little more than an hour. The scene there was eerie; all around us were barren fresh lava rocks. Beyond the vents themselves, not much lives down there except for occasional weird-looking, eel-like fish.
The temperature reading at the seafloor was about 1.6° Celsius (35° Fahrenheit), barely above the freezing point. We started on our long list of scientific tasks to accomplish during the six to eight hours at the bottom.
Crab Spa was the first stop. This is the name of a lukewarm hot spring venting fluids with temperatures of about 25° C (77° F). It hosts numerous tubeworms, mussels, and, as you may have guessed, crabs, which, unlike their colorful shallow-dwelling counterparts, are all white. They spent most of their time around vent orifices that were spewing warm water out of the seafloor. The crabs were trying to grab pieces of white mats made of microbes and shove them into their tiny mouths. It was a pretty amusing scene to witness.
Vent-SID in action
After we took some fluid samples from Crab Spa vents, our next task was to deploy a newly developed instrument called the Vent-SID, short for Vent-Submersible Incubation Device. Sievert and his colleagues are studying the metabolic activities of microbes in vents. To date, scientists have conducted this research by collecting vent fluids, bringing them back on board the ship in incubation devices, and trying their best to simulate the pressure and temperature conditions found at vents.
Investigating these microbial activities through experiments conducted in situ is a better way of understanding what is actually happening in nature. But that’s a daunting challenge. Vent-SID is designed to be placed near vents and suck vent fluids into an incubator chamber. Inside, microbes in the vent fluids carry on their normal biochemical activities, which Vent-SID can measure. The key is that all these chemical reactions are carried out in situ, under the conditions in which they normally happen.
Finding a perfect spot to place the 3.5-by-2.5-by-8-foot-tall Vent-SID was not easy. Yet Pat Hickey, a veteran Alvin pilot with more than 680 dives, did not take long to use Alvin’s two manipulator arms and put Vent-SID right above a Crab Spa vent orifice. Then he maneuvered a temperature probe into the venting fluids to find the best place for the Vent-SID to take fluids into its incubator chamber.
Vent-SID would automatically start filling the chambers with vent fluids (along with the microbes in them) and begin its job as an in situ robotic lab, performing experiments scientists typically do either onboard the ship or back in a lab on land—including injecting chemical tracers, collecting microbes after incubation, and preserving samples for genetic materials. The experiments will help elucidate the kinds of microbes down there and the types and rates of biochemical reactions they perform—in an effort to understand the critical roles microbes play in sustaining vent ecosystems.
Chimneys on the seafloor
We had several more vent sites to visit on our dive. Our next stop was a spectacular site called Bio9. When we approached the area, the clear water was suddenly filled with what looked like dense black smoke. Then it was as if that velvety black curtain was pulled open, and we could see several enormous structures that looked like rocky chimneys spewing the black smoke. These tall structures form when the hot vent fluids meet cold seawater and almost instantly solidify. The “smoke” spewing out is actually vent fluid filled with minerals dissolved from subseafloor rocks. Some of the chimneys were extinct, and others were actively emitting very hot fluids.
Black-smoker chimneys form when the vents fluids are hot. Fluids emanating from Bio9 can be as hot as 360° C (680° F). The fluids and inner chimney walls are too hot for microbes, as life can tolerate temperatures up to only 122° C (252° F). But the fluids cool down quickly when they spew into seawater, creating a more hospitable environment for life to thrive.
Fluids from high-temperature vents such as Bio9 are also particularly important for my research, because they are too hot for living things, such as microbes. So any ammonia in them cannot have been produced by chemical reactions involving microbes. That is the type of ammonia that billions of years ago could have been converted into amino acids that led to the first life on Earth.
We proceeded to collect fluid samples from Bio9 with what we call Major samplers. We had a lot of samples from high-temperature vent sites. So we called it a successful day, dropped Alvin’s weights, and floated back to the surface.
A hard day’s night
My long day in the submersible was no excuse for not having a long night in the lab.
My colleagues and I worked as fast as we could in clockwork fashion to get the vent fluids out of the samplers and into appropriate bottles and then process and store them away either in the refrigerator or freezer.
These samples were particularly foul-smelling. Every time we cracked open the Major samplers to take out the vent fluids, the smell of sulfide permeated the room. It is the same rotten-egg smell you experience from muddy salt marshes. This sulfide, as well as the ammonia that I measure, provide the chemical energy that vent microbes use to live and grow.
But this repugnant smell strangely reminded me of the childhood summers I spent at my grandparents’ home. In their backyard stood a dense mangrove swamp reeking of the same sulfide smell. My life seemed to have come full circle.
My teammates and I carefully extracted fluids from the Major samplers, one by one. We measured the fluids’ pH and salinity—the first line of evidence to confirm the integrity of the samples we had collected.
Most low-temperature vent samples have a salinity similar to seawater. Their pH, a measure of how acidic they are, ranges between 5 and 6, like that of black coffee. On the other hand, high-temperature vent fluids from the black smokers in this area tend to be fresher and have a pH of 3 to 4, like that of vinegar used in cooking.
It’s the high-temperature fluids that I am after.
Isotopes as a fingerprinting tool
Work does not end at sea. Back in the lab at WHOI, we analyze our precious samples with an isotope ratio mass spectrometer (IRMS), hoping to reveal the unique chemical fingerprints hidden within compounds found in the vent fluids. These chemical fingerprints are isotopes—forms of chemical elements with different masses.
I study nitrogen isotopes—more precisely, the ratios between the heavier and scarcer nitrogen-15 to the lighter and more abundant nitrogen-14. Scientists have used these nitrogen isotope ratios for decades to study food webs, trace fertilizer pollution in watersheds, or study the many chemical reactions involving nitrogen that happen in the ocean.
With my Ph.D. advisor, WHOI biogeochemist Scott Wankel, I am investigating the nitrogen-isotope fingerprints to reveal what chemical processes are happening below the seafloor to give rise to ammonia in hydrothermal vent fluids.
I also worked with WHOI geochemist Jeff Seewald to set up closely controlled lab experiments to learn more about ammonia-producing processes. I conduct these reactions within a bag made of gold. Gold is malleable and can withstand high pressure and heat, and it does not react with the other chemicals. So it makes a fine container to put in our reactor at high temperatures and pressures similar to those at seafloor vents.
There are many chemical pathways that can produce ammonia. Which is the major one? What conditions of pressure, heat, rocks, geological features, or other factors favor this pathway versus another? What scenario is more likely to make ammonia? What’s going on at present that would let us infer what might have been happening in ancient oceans to spark the emergence of life?
Like any problem in science, understanding the origin of ammonia in vent fluids is not straightforward. We are just beginning to uncover the geochemical processes beneath the seafloor that produce ammonia. Analyses of fluids from vents in different oceans may show other scenarios beyond what we see at Bio9 and other sites in the Pacific.
The more I explore the subject, the more I find questions begging for answers. And just as during the sleepless hours before my Alvin dive, these scientific questions from time to time keep me awake at night.
This research was funded by the National Science Foundation. Net Charoenpong is supported by the NSF, the J. Seward Johnson Fund, and a Thailand Ministry of Science and Technology fellowship.
In the 1930s, the Cape Cod Mosquito Control Project dug approximately 1,500 miles of ditches across marshes on the Cape to drain their water and reduce the number of ponds where mosquitoes can breed. Woods Hole Oceanographic Institution biogeochemist Amanda Spivak is studying how this and other management decisions have changed the ability of coastal marshes to store carbon and protect against sea level rise.
