Constantine Alexander's Journal

The ocean is losing its breath

In broadest view yet of world's low oxygen, scientists reveal dangers and solutions.

Low oxygen caused the death of these corals and others in Bocas del Toro, Panama. The dead crabs pictured also succumbed to the loss of dissolved oxygen. Credit: Arcadio Castillo/Smithsonian.

In the past 50 years, the amount of water in the open ocean with zero oxygen has gone up more than fourfold. In coastal water bodies, including estuaries and seas, low-oxygen sites have increased more than 10-fold since 1950. Scientists expect oxygen to continue dropping even outside these zones as Earth warms.

To halt the decline, the world needs to rein in both climate change and nutrient pollution, an international team of scientists including Lisa Levin, a biological oceanographer at Scripps Institution of Oceanography at the University of California San Diego, asserted in a new paper published Jan. 4 in Science.

"Oxygen is fundamental to life in the oceans," said Denise Breitburg, lead author and marine ecologist with the Smithsonian Environmental Research Center. "The decline in ocean oxygen ranks among the most serious effects of human activities on the Earth's environment."

"It's a tremendous loss to all the support services that rely on recreation and tourism, hotels and restaurants and taxi drivers and everything else," said Levin. "The reverberations of unhealthy ecosystems in the ocean can be extensive."

The study came from a team of scientists from GO2NE (Global Ocean Oxygen Network), a new working group created in 2016 by the United Nation's Intergovernmental Oceanographic Commission. The review paper is the first to take such a sweeping look at the causes, consequences and solutions to low oxygen worldwide, in both the open ocean and coastal waters. The article highlights the biggest dangers to the ocean and society, and what it will take to keep Earth's waters healthy and productive.

The Stakes

"Approximately half of the oxygen on Earth comes from the ocean," said Vladimir Ryabinin, executive secretary of the International Oceanographic Commission that formed the GO2NE group. "However, combined effects of nutrient loading and climate change are greatly increasing the number and size of 'dead zones' in the open ocean and coastal waters, where oxygen is too low to support most marine life."

In areas traditionally called "dead zones," like those in Chesapeake Bay and the Gulf of Mexico, oxygen plummets to levels so low many animals suffocate and die. As fish avoid these zones, their habitats shrink and they become more vulnerable to predators or fishing. But the problem goes far beyond "dead zones," the authors point out. Even smaller oxygen declines can stunt growth in animals, hinder reproduction and lead to disease or even death. It also can trigger the release of dangerous chemicals such as nitrous oxide, a greenhouse gas up to 300 times more powerful than carbon dioxide, and toxic hydrogen sulfide. While some animals can thrive in dead zones, overall biodiversity falls.

Climate change is the key culprit in the open ocean. Warming surface waters make it harder for oxygen to reach the ocean interior. Furthermore, as the ocean as a whole gets warmer, it holds less oxygen. In coastal waters, excess nutrient pollution from land creates algal blooms, which drain oxygen as they die and decompose. In an unfortunate twist, animals also need more oxygen in warmer waters, even as it is disappearing.

People's livelihoods are also on the line, the scientists reported, especially in developing nations. Smaller, artisanal fisheries may be unable to relocate when low oxygen destroys their harvests or forces fish to move elsewhere. In the Philippines, fish kills in a single town's aquaculture pens cost more than $10 million. Coral reefs, a key tourism attraction in many countries, also can waste away without enough oxygen.

Some popular fisheries could benefit, at least in the short term. Nutrient pollution can stimulate production of food for fish. In addition, when fish are forced to crowd to escape low oxygen, they can become easier to catch. But in the long run, this could result in overfishing and damage to the economy.

Low-oxygen zones are spreading around the globe. Red dots mark places on the coast where oxygen has plummeted to 2 milligrams per liter or less, and blue areas mark zones with the same low-oxygen levels in the open ocean. Credit: GO2NE working group. Data from World Ocean Atlas 2013 and provided by R. J. Diaz.

Winning the War: A Three-Pronged Approach

To keep low oxygen in check, the scientists said the world needs to take on the issue from three angles:

Address the causes: nutrient pollution and climate change. While neither issue is simple or easy, the steps needed to win can benefit people as well as the environment. Better septic systems and sanitation can protect human health and keep pollution out of the water. Cutting fossil fuel emissions not only cuts greenhouse gases and fights climate change, but also slashes dangerous air pollutants like mercury.

Protect vulnerable marine life. With some low oxygen unavoidable, it is crucial to protect at-risk fisheries from further stress. According to the GO2NE team, this could mean creating marine protected areas or no-catch zones in areas animals use to escape low oxygen, or switching to fish that are not as threatened by falling oxygen levels. Improve low-oxygen tracking worldwide. Scientists have a decent grasp of how much oxygen the ocean could lose in the future, but they do not know exactly where those low-oxygen zones will be. Enhanced monitoring, especially in developing countries, and numerical models will help pinpoint which places are most at risk and determine the most effective solutions.

"This is a problem we can solve," Breitburg said. "Halting climate change requires a global effort, but even local actions can help with nutrient-driven oxygen decline." As proof Breitburg points to the ongoing recovery of Chesapeake Bay, where nitrogen pollution has dropped 24 percent since its peak thanks to better sewage treatment, better farming practices and successful laws like the Clean Air Act. While some low-oxygen zones persist, the area of the Chesapeake with zero oxygen has almost disappeared. "Tackling climate change may seem more daunting," she added, "but doing it is critical for stemming the decline of oxygen in our oceans, and for nearly every aspect of life on our planet."

Citation: Denise Breitburg, Lisa A. Levin, Andreas Oschlies, Marilaure Gregoire, Francisco P. Chavez, Daniel J. Conley, Veronique Garcon, Denis Gilbert, Dimitri Gutierrez, Kirsten Isensee, Gil S. Jacinto, Karin E. Limburg, Ivonne Montes, S.W.A. Naqvi, Grant C. Pitcher, Nancy N. Rabalais, Michael R. Roman, Kenneth A. Rose, Brad A. Seibel, Maciej Telszewski, Moriaki Yasuhara & Jing Zhang; Declining oxygen in the global ocean and coastal waters; Science, Vol. 359, Issue 6371, eaam7240 (5 January 2018); DOI: 10.1126/science.aam7240.

Contact: Rob Monroe
University of California - San Diego

 

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CO2 removal cannot save the oceans if we pursue business as usual

New study identifies thermometer for global ocean (Constantine Alexander's Journal)

Shifting winds, ocean currents doubled endangered Galápagos penguin population

Scientists find surprising evidence of rapid changes in the Arctic

Diminishing sea ice near the Arctic coast leaves more open water near the coast for winds to create waves. The increased wave action reaches down and stirs up sediments on shallow continental shelves, releasing radium and other chemicals that are carried up to the surface and swept away into the open ocean by currents such as the Transpolar Drift. A new study found surprising evidence that climate change is rapidly causing coastal changes in the Arctic that could have significant impacts on Arctic food webs and animal populations. (Natalie Renier, Woods Hole Oceanographic Institution).

Scientists have found surprising evidence of rapid climate change in the Arctic: In the middle of the Arctic Ocean near the North Pole, they discovered that the levels of radium-228 have almost doubled over the last decade.

The finding indicates that large-scale changes are happening along the coast--because the source of the radium is the land and shallow continental shelves surrounding the ocean. These coastal changes, in turn, could also be delivering more nutrients, carbon, and other chemicals into the Arctic Ocean and lead to dramatic impacts on Arctic food webs and animal populations.

The research team, led by Woods Hole Oceanographic Institution (WHOI), suspects that melting sea ice has left more open water near the coast for winds to create waves. The wave action reaches down to the shallow shelves and stirs up sediments, releasing radium that is carried to the surface and away into the open ocean. The same mechanism would likely also mobilize and deliver more nutrients, carbon, and other chemicals into the Arctic Ocean, fueling the growth of plankton at the bottom of the food chain. That, in turn, could have significant impacts on fish and marine mammals and change the Arctic ecosystem.

The study was published Jan. 3, 2018, in the journal Science Advances. The research team included Lauren Kipp, Matthew Charette, and Paul Henderson (WHOI), Willard Moore (University of South Carolina), and Ignatius Rigor (University of Washington).

Scientists have long used radium-228 to track the flow of material from land and sediments into the ocean. It is a naturally occurring isotope produced by the radioactive decay of thorium in sediments. But unlike thorium, it dissolves into water, where scientists can track the sources, amounts, rates, and direction of its flow, said Kipp, who is lead author of the study and a graduate student in the MIT-WHOI Joint Program in Oceanography.

Kipp led efforts to measure radium at 69 locations from the western edge of the Arctic Ocean to the Pole on a two-month voyage aboard the icebreaker Healy in the summer of 2015. The cruise was part of the international GEOTRACES program, which aims to measure chemical tracers in the world's ocean to understand ocean circulation and provide a baseline to assess future chemical changes in the oceans. The U.S. GEOTRACES program and this study are both funded by the National Science Foundation.

Scientists aboard the icebreaker Healy measured seawater chemistry across the Arctic Ocean and found that levels of radium-228 have almost doubled over the last decade in the middle of the ocean. The radium was transported from land and shallow continental shelves by currents such as the Transpolar Drift. The surprising finding is evidence that rapid climate change is causing large-scale changes along the Arctic coast, such as diminishing sea ice. These coastal changes, in turn, could also deliver more nutrients, carbon, and other chemicals into the Arctic Ocean and have significant impacts on the Arctic food web. (Natalie Renier, Woods Hole Oceanographic Institiution).

To their surprise, the research team found that radium-228 concentrations in the central Arctic Ocean had increased substantially since measurements had last been made in 2007. What was its source and why had it increased?

The team investigated the trajectories of sea ice drifting in the ocean and saw a pattern of ice--and hence water--flowing northward from the vast northern coast of Russia toward the middle of the Arctic Ocean, where the radium concentrations had increased. The pattern aligned with the Transpolar Drift, a powerful current flowing in same direction that could transport radium from coastal sources.

They concluded that the excess radium had to have come from sediments in the East Siberian Arctic Shelf off Russia, the largest continental shelf on Earth. It is relatively shallow, with an average depth of 170 feet, but it extends 930 miles off shore and contains a vast reservoir of radium and other chemical compounds.

Something had to have changed along the coast to explain the dramatic surge in radium in the middle of the Arctic Ocean. The scientists theorize that a warming Arctic environment has reduced sea ice cover, allowing for more wave action that stirs up sediments and mobilizes more radium.

But there are other possible contributing factors that are causing changes over the shelf, the scientists say. More wave action can also cause more coastline erosion, adding more terrestrial sediment into the ocean. Warming temperatures can thaw permafrost, liberating more material into the ocean, and increasing river and groundwater runoff can carry more radium, nutrients, carbon, and other material into the Arctic.

"Continued monitoring of shelf inputs to Arctic surface waters is therefore vital to understand how the changing climate will affect the chemistry, biology, and economic resources of the Arctic Ocean," the study's authors wrote.

Data coverage over the East Siberian Shelf is currently very limited, so it is important to conduct more studies in this region in order to pinpoint the direct causes of the increased shelf inputs and allow future monitoring. "Evidence from Kipp and co-workers for substantial ongoing change in the chemical environment of the Arctic Ocean emphasizes the need for sustained study of these changes and of the processes involved," said Bob Anderson, an Ewing-Lamont Research Professor at the Lamont-Doherty Earth Observatory of Columbia University and the director of the U.S. GEOTRACES Program Office. "It would be great if related efforts by marine geochemists in Russia could be integrated with future studies by other nations, for example under the auspices of the international GEOTRACES program."

Citation: Lauren Kipp, Matthew Charette, Paul Henderson, Willard Moore, and Ignatius Rigor; Science Advances , Vol. 4 no. 1 eaao 1302 (o3 January 2018); DOI: 10.1126/sciadv.aao1302.

Woods Hole Oceanographic Institution

 

New study identifies thermometer for global ocean

Ross Beaudette of the Severinghaus lab at Scripps Oceanography (right) and Jeremy Miner drill a shallow ice core during WAIS Divide project. Credit: Bradley Markle.

There's a new way to measure the average temperature of the ocean thanks to researchers at Scripps Institution of Oceanography at the University of California San Diego. In an article published in the Jan. 4, 2018, issue of the journal Nature, geoscientist Jeff Severinghaus and colleagues at Scripps Oceanography and institutions in Switzerland and Japan detailed their ground-breaking approach.

Determining changes in the average temperature of the entire world's ocean has proven to be a nearly impossible task due to the distribution of different water masses. Each layer of water can have drastically different temperatures, so determining the average over the entirety of the ocean's surface and depths presents a challenge.

Severinghaus and colleagues were able to bypass these obstacles by determining the value indirectly. Instead of measuring water temperature, they determined the ratio of noble gases in the atmosphere, which are in direct relation to the ocean's temperature.

"This method is a radically new way to measure change in total ocean heat," said Severinghaus. "It takes advantage of the fact that the atmosphere is well-mixed, so a single measurement anywhere in the world can give you the answer."

In the study, the scientists measured values of the noble gases argon, krypton, and xenon in air bubbles captured inside ice in Antarctica. As the oceans warm, krypton and xenon are released into the atmosphere in known quantities. The ratio of these gases in the atmosphere therefore allows for the calculation of average global ocean temperature.

Measurements were taken from ice samples collected during the West Antarctic Ice Sheet (WAIS) Divide coring project, of which Severinghaus is a leader. Over the course of six field seasons in Antarctica, a drill removed ice in cylindrical samples 3.7 meters (just under 9 feet) in length. The final sample was taken at a depth of 3,405 meters (over 11,000 feet) in 2011. This record spans nearly 100,000 years and the age of the layers can be determined to within 50 years. Earth's atmosphere mixes on a scale of weeks to months, so a measurement of these air bubbles gives what is essentially a global average. For this study, scientists focused on samples 8,000 to 22,000 years old, and collected data in increments averaging 250 years in resolution.

New insights into the glaciation cycles that occurred on Earth long before humans began affecting the temperature of the atmosphere and oceans are now possible using the technique of measuring noble gas quantities. The study determined that the average global ocean temperature at the peak of the most recent ice age was 0.9 ºC (33.6 ºF). The modern ocean's average temperature is 3.5 ºC (38.3 ºF). The incremental measurements between these data points provide an understanding of the global climate never before possible.

"The reason this study is so exciting is that previous methods of reconstructing ocean heat content have very large age uncertainties, [which] smooths out the more subtle features of the record," said co-author Sarah Shackleton, a graduate student in the Severinghaus lab at Scripps. "Because WAIS Divide is so well dated, this is the first time that we've been able to see these subtle features in the record of the deglaciation. This helps us better understand the processes that control changes in ocean heat content."

This paper is the result of fifteen years of work for Severinghaus, along with graduate students and postdoctoral scholars in his lab. Discussions with another professor at Scripps, atmospheric scientist Ralph Keeling, brought about the idea. Keeling studies the argon levels in the atmosphere to get a similar record of ocean heat going back a few decades. However, air bubbles trapped in ice don't preserve argon levels accurately. Severinghaus discovered that xenon and krypton are well preserved in ice cores, which provides the temperature information that can then be used by scientists studying many other aspects of the earth's oceans and atmosphere over hundreds of thousands of years.

Going forward, the ratios of these same noble gases can be determined from atmospheric samples taken anywhere in the world. For example, a measurement from the Ellen Browning Scripps Memorial Pier in La Jolla represents a global average of ocean temperature. Severinghaus hopes to fine tune the procedure.

"Our precision is about 0.2 ºC (0.4 ºF) now, and the warming of the past 50 years is only about 0.1 ºC," he said, adding that advanced equipment can provide more precise measurements, allowing scientists to use this technique to track the current warming trend in the world's oceans.

Up to this point, the best estimates have come from the Argo program, a network of more than 3,800 robotic floats distributed around the world's oceans that measures temperature and other properties and reports the data via satellite.

Scripps operates the Argo Project Office and is one of dozens of institutions worldwide participating since its inception in 2000. The floats, however, are primarily limited to ice-free areas and only descend to a depth of 2,000 meters (6,500 feet), leaving large key areas unstudied in the quest to obtain a global ocean temperature average.

With this study, Severinghaus and colleagues have shown that measurements of noble gases in the atmosphere provide the historical record long sought by the scientific community, and can be further optimized to gain insights into modern ocean temperature changes as well.

Citation: Bernhard Bereiter, Sarah Shackleton, Daniel Baggenstos, Kenji Kawamura & Jeff Severinghaus; Mean global ocean temperatures during the last glacial transition; Nature 553, 39–44 (04 January 2018); DOI:10.1038/nature25152.

This research was supported by the National Science Foundation, and the Swiss National Science Foundation.

Contact: Lauren Fimbres Wood
University of California - San Diego

 

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The Caribbean is stressed out

But there is hope, according to data from 25-year monitoring program.

Karen H. Koltes, Ph.D, records data at a CARICOMP site. By measuring ocean health in the same way at sites across the Caribbean, it's possible to understand where coastal environments are the most stressed out. "If people get their act together very soon, there is still hope of reversing some of these changes," said Rachel Collin, director of the Bocas del Toro Research Station at the Smithsonian Tropical Research Institute, one of the participating marine-monitoring stations. Credit: Karen Koltes.

Forty percent of the world's 7.6 billion people live in coastal cities and towns. A team including Smithsonian marine biologists just released 25 years of data about the health of Caribbean coasts from the Caribbean Coastal Marine Productivity Program (CARICOMP). The study provides new insights into the influence of both local and global stressors in the basin, and some hope that the observed changes can be reversed by local environmental management.

The largest, longest program to monitor the health of the Caribbean coastal ecosystems, CARICOMP revealed that water quality decreased at 42 percent of the monitoring stations across the basin. However, significant increases in water temperature, expected in the case of global warming, were not detected across sites.

"We're seeing important changes in local conditions, like decreases in visibility associated with declining water quality and the increasing presence of people, but we're not picking up global-scale changes, like climate warming," said Iliana Chollett, post-doctoral fellow at the Smithsonian Marine Conservation Program in Fort Pierce, Fla..

"Our data set did not reveal significant increases in water temperature," Chollett said. "Satellites only measure temperature at the surface. Underwater temperatures are much more variable, and it may take decades of data to reveal a significant change, so we're not sure if this means that we just don't have enough data to detect it yet."

More than 25 years ago, in 1992, researchers at institutions across the Caribbean began to set up stations to gather environmental data on mangroves, seagrass beds and coral reefs at coastal sites.

They began to take weekly measurements of water temperature, salinity and visibility at stations placed to avoid direct interference from cities, towns and other direct human impacts.

The team gathered CARICOMP data from 29 sites in Barbados, Belize, Bermuda, Bonaire, Colombia, Costa Rica, Florida, Jamaica, Mexico, Panama, Puerto Rico, Saba, and Venezuela and organized it into a single data set. This includes data taken for periods from three years, at stations added to the network more recently, to 22 years.

Despite attempts to locate monitoring sites in places not affected by human activities, the stations are picking up signals of human influence throughout the Caribbean basin.

"One positive implication of this report is people are capable of dealing with local change by regulating pollution and runoff," said Rachel Collin, director of the Bocas del Toro Research Station at the Smithsonian Tropical Research Institute, one of the participating marine-monitoring stations. "If people get their act together very soon, there is still hope of reversing some of these changes."

Citation: Iliana Chollett, Rachel Collin, Carolina Bastidas, Aldo Cróquer, Peter M. H. Gayle, Eric Jordán-Dahlgren, Karen Koltes, Hazel Oxenford, Alberto Rodriguez-Ramirez, Ernesto Weil, Jahson Alemu, David Bone, Kenneth C. Buchan, Marcia Creary Ford, Edgar Escalante-Mancera, Jaime Garzón-Ferreira, Hector M. Guzmán, Björn Kjerfve, Eduardo Klein, Croy McCoy, Arthur C. Potts, Francisco Ruíz-Rentería, Struan R. Smith, John Tschirky & Jorge Cortés; Widespread local chronic stressors in Caribbean coastal habitats; PLOS ONE, 2017; 12 (12): e0188564; DOI: 10.1371/journal.pone.0188564.

The MacArthur Foundation, the Coral Reef Initiative of the U.S. Department of State, UNESCO and the U.S. National Science Foundation supported the CARICOMP network as did the individual institutions that run the monitoring stations.

Contact: Beth King, Smithsonian Tropical Research Institute

 

Fish and ships: Vessel traffic reduces communication ranges for Atlantic cod, haddock

Maps showing (a) locations of the three recording sites within Massachusetts Bay and Stellwagen Bank National Marine Sanctuary north of Cape Cod in relation to the adjacent coast of Massachusetts, (b) AIS vessel tracks over the three-month recording period for both the Atlantic cod winter spawning site and the haddock winter spawning site within a 10 nautical mile radius. White lines mark the boundaries of Stellwagen Bank National Marine Sanctuary.
Location of the Spring Cod Conservation Zone, the site of the Atlantic cod spring spawning recording location.
Location of the Atlantic cod winter spawning recording location.
Location of the haddock winter spawning recording location.
Port of Boston traffic separation scheme.
Maps created in ArcMAP 10.3.1 by Jenni Stanley of NOAA Fisheries/NEFSC and Mike Thompson of NOAA/SBNMS

NOAA scientists studying sounds made by Atlantic cod and haddock at spawning sites in the Gulf of Maine have found that vessel traffic noise is reducing the distance over which these animals can communicate with each other. As a result, daily behavior, feeding, mating, and socializing during critical biological periods for these commercially and ecologically important fish may be altered, according to a study published in Scientific Reports.

Three sites in Massachusetts Bay, two inside Stellwagen Bank National Marine Sanctuary (SBNMS) and one inshore south of Cape Ann, were monitored for three months by researchers at the Northeast Fisheries Science Center (NEFSC) laboratory in Woods Hole, Mass. and at the sanctuary offices in Scituate, Mass. Vocalizations, such as Atlantic cod grunts and haddock knocks, were recorded by bottom-mounted instruments at each site during spawning in winter and spring.

"We looked at the hourly variation in ambient sound pressure levels and then estimated effective vocalization ranges at all three sites known to support spawning activity for Gulf of Maine cod and haddock stocks," said Jenni Stanley, a marine research scientist in the passive acoustics group at the NEFSC and SBNMS and lead author of the study. "Both fluctuated dramatically during the study. The sound levels appear to be largely driven by large vessel activity, and we found a signification positive correlation with the number of Automatic Identification System (AIS) tracked vessels at two of the three sites."

AIS is an automatic tracking system, used on ships and by vessel traffic services. It provides information on a vessel, such as its unique identification number, position, course and speed, which can be displayed on a shipboard radar or electronic chart display.

Ambient sounds - those in the surrounding environment - include animals vocalizing, physical sounds such as wind and water movement or geological activity, and human-produced sound from ships and marine construction. Many marine animals use ambient sound to navigate, to choose where to settle, or to modify their daily behaviors including breeding, feeding and socializing.

Cod grunts were present for 100 percent of the spring days and 83 percent of the winter days. Haddock knocks were present for 62 percent of the winter days within the three-month sampling period. However, ambient sound levels differed widely at the three sites, both on an hourly and daily time scale. The Atlantic cod winter spawning site, nearest the Boston shipping lanes, had the highest sound levels, while the Atlantic cod spring spawning site inshore south of Gloucester, Mass. had the lowest. Sound levels in the haddock winter spawning site, further offshore in the sanctuary, were in the middle of the range detected in the study.

Marine Autonomous Recording Units, or MARUs, used to record sound on the ocean floor. Photo credit: NOAA Fisheries/NEFSC

Study data were also used to calculate the estimated distance a fish vocalization would be heard at each of the spawning sites. The effective radius ranged widely, from roughly 4 to 70 feet, and was largely dependent on the number of tracked vessels within a 10 nautical mile radius of the recording sites.

Lower-level, chronic exposure to increased ambient sound from human activities is one of the most widespread, yet poorly understood, factors that could be changing fish behavior. If they cannot hear as well as they need to, then sound signals from other fish can be lost, compromised, or misinterpreted in ways that can cause a change in behavior. Since Atlantic cod, for example, vocalize to attract mates and listen for predators, not hearing those signals could potentially reduce reproductive success and survival.

"Anthropogenic sound in certain ocean regions has increased considerably in recent decades due to various human activities such as global shipping, construction, sonar, and recreational boating," Stanley said. "As ocean sound increases, so does the concern for its effects on populations of acoustic signalers, which range from invertebrates to marine mammals. We don't know if or to what extent specific species can adapt or adjust their acoustic signals to compete in this environment."

In addition to Stanley, other researchers involved in the study were Sofie Van Parijs at the NEFSC's Woods Hole Laboratory and Leila Hatch at Stellwagen Bank National Marine Sanctuary.

Citation: Jenni A. Stanley, Sofie M. Van Parijs & Leila T. Hatch; Underwater sound from vessel traffic reduces the effective communication range in Atlantic cod and haddock; Scientific Reports 7, Article Number: 14633 (7 November 2017); DOI: 10.1038/s41598-017-14743-9.

Contact: Shelley Dawicki
NOAA Northeast Fisheries Science Center

 

Conserving coral communities

Study suggests coral restoration projects can help restore fish communities.

A diversity of corals. Photo by Toby Hudson (CC BY-SA 3.0).

Spending hours a day diving in and around the coral reefs off St. Croix in the U.S. Virgin Islands sounds like the stuff of a dream vacation, but for Annie Opel it was serious business.

As part of her undergraduate thesis, Opel spent much of her time in the water working on a study showing efforts to restore coral reefs have a positive impact on local fish populations, both in the short term and over time. The study is published in the December issue of Marine Biology with Opel as first author, a rare accomplishment for an undergraduate.

"Reefs are not only biologically important - more than 4,000 species of fish rely on these ecosystems - but they're also really important for humans," Opel said. "We depend on them for commercial and recreational fisheries, they provide protection for coastal communities and they bring in a great deal of money through tourism.

"But right now they're threatened by a number of anthropogenic inputs, from pollution to the effects of climate change," Opel said. "Coral reefs have experienced bleaching and mass mortality all over the world, causing ecosystem degradation that affects the marine life that rely on the reefs to survive."

While there have been efforts to address the problem by transplanting corals grown in underwater "nurseries" to damaged reefs, the effectiveness of such restoration projects on Caribbean reefs has never been rigorously studied, Opel said.

"In St. Croix, they've been restoring corals since 2009," Opel said. "(But) no one is really looking at what's happening after the fact...so no one knows if this is an efficient way to restore (those) reef systems."

What she found, Opel said, is that in as little as a week after creating experimental coral beds, significantly more fish and a greater diversity of species could be found. The study also showed that, over time, the fish community changed as additional species began visiting the sites.

"Overall, it's a success story - we out-planted corals and there were more fish," she said. "That's really exciting and something people took for granted in these restoration projects, but no one had quantified it before. I think it's going to be interesting for future studies to use this as a benchmark to know what's going on after transplanting corals."

The project was a natural fit for Opel, as it allowed her to combine both her interest in ocean conservation and the sciences.

During a gap year after finishing high school, Opel spent time in St. Croix, working with The Nature Conservancy on coral restoration projects. As a sophomore at Harvard, she joined the lab of Colleen M. Cavanaugh, the Edward C. Jeffrey Professor of Biology in the department of Organismic and Evolutionary Biology, and later proposed the coral study for her senior honors thesis. Prof. Cavanaugh took on the challenge of advising Annie on her own independent research with the help of her Post-doctoral Fellow, Dr. Joey Pakes Nelson, an invertebrate biologist and ecologist, and a former Post-doc, Dr. Randi Rotjan, a coral reef expert now an assistant professor at Boston University.

"This work was really cool for a variety of reasons," said postdoctoral fellow Joey Pakes Nelson. "As a global community, we spend a lot of money on coral reef restoration, but few studies describe how this practice affects the reef community, so Annie's work provides justification for investments in this type of conservation.

"When it came time to choose a thesis topic, Annie wanted to combine her love of research with her love of coral," she added. "She had great resources because of her work in the Nature Conservancy, she knew about transplanting corals, she had diving experience and she had a great question."

But having a great idea, however, didn't make it any easier to execute.

"I went down to St. Croix in March over spring break and in collaboration with other researchers, out-planted four two-by-two meter plots of an endangered species of coral found in the Caribbean called Acropora cervicornis," Opel said. "We also designated control plots ten and 20 meters away."

Opel returned to the island at the end of the academic year to plant four additional plots and began the hard work of collecting data almost entirely on her own.

"Each survey day, I spent two hours underwater where I took five minute surveys on each of my 16 plots. I sat there with underwater paper and a clipboard and I would basically mark every fish I saw for that five minutes," Opel said. "It was a steep learning curve, because I needed to learn how to identify every species of fish by sex and age before I started taking my surveys. I took surveys three times a week for all 16 plots, and I counted something like 15,000 fish in total, so it was a lot of sitting underwater in my bright orange wetsuit counting and identifying fish."

One of the most challenging parts of the project, she said, was finding partners to accompany her on dives.

"For safety reasons, you always dive with another person," Opel said. "But it's not like I had an assistant or anyone working with me, so I had to crowdsource my volunteers. I asked around at local dive shops in St. Croix and got put in contact with a lot of great people that wanted to help me with my research. One day my dad even came with me, so that was really special. One of my favorite parts of the paper is the acknowledgments, because I got the chance to thank all the volunteer divers and all of the people that helped make this project happen. And I am really thankful to have had three rock star female scientists to mentor me through this academic journey".

Citation: Opel, A.H., Cavanaugh, C.M., Rotjan, R.D. Joey Pakes Nelson;  Marine Biology 164:221 (2 November 2017); DOI: 10.1007/s00227-017-3248-0.

This research was supported with funding from the Harvard College Office of Undergraduate Research and Fellowships, Harvard University Center for the Environment, Museum of Comparative Zoology, Marine Conservation Action Fund and the National Science Foundation.

Contact: Peter Reuell
Harvard University

 

World War I era maps help track history of kelp forests in Pacific Northwest

Ecologist uses maps produced before World War I, which have quite a history of their own, to track the growth of kelp beds in the Pacific Northwest over the last century.

Prof. Cathy Pfister compares 100-year-old kelp survey maps to modern surveys, finding that most modern kelp beds along the Washington coast have remained as abundant.

In the early 1900s, the U.S. Department of Agriculture recognized a problem. The United States relied heavily on fertilizer to grow crops and support its burgeoning economy, yet a crucial ingredient for fertilizer - potash, a mixture of potassium and salts - was mined almost exclusively in Germany. German mines supplied nearly the entire world's supply of potash, and at the time the U.S. used about a fifth of its output, half of the amount exported from Germany.

"It is obviously undesirable that the United States should be dependent upon any other nation for its supply of a necessity," wrote Frank Cameron, an officer "in charge of chemical, physical and fertilizer investigations" for the USDA, in a 1915 report.

Seeking ways to ease this dependency, the USDA commissioned several surveys of an alternative source of potash: kelp beds in the Pacific Northwest. The large, hardy seaweed is a natural source of potassium, nitrogen and salts, and had been used as fertilizer for years by Native Americans and settlers. If kelp could be harvested and processed in large enough quantities, it could be a viable source of potash to offset German imports.

So, the USDA sent surveyors -- including George Rigg, an ecologist from the University of Washington -- to map the kelp beds along the coast of California, Oregon, Washington and Alaska. Rigg set out in a yacht with a 40-horsepower motor and mapped the coastline around Puget Sound in 1911-12. More than 100 years later, scientists at the University of Chicago used these maps to track historical changes in the kelp forests of the Pacific Northwest.

As it turned out, the original maps from the kelp surveys ended up at the University of Chicago Library, where Cathy Pfister, PhD, professor in the department of ecology and evolution, discovered them. She worked with the library's preservation staff to digitize the maps, and compared them to modern surveys conducted by the Washington State Department of Natural Resources over the past 26 years.

What they found is a relatively rare positive story when it comes to ecological studies in a time of accelerating climate change. The abundance of most modern kelp beds along the Washington coast has remained constant over the last century despite a seawater temperature increase of 0.72 degrees Celsius. The few exceptions are kelp beds closest to Puget Sound, Seattle and Tacoma.

"Kelp are a robust and resilient structure. You can see that in the data, as long as they have access to good water quality and waves flush through them, then they persist," Pfister said.

 

Pfister and her team also studied the competition among kelp species in the area. While the kelp beds were persistent over the decades, their populations could fluctuate greatly from year to year. There are two dominant species -- the annual bull kelp and the perennial giant kelp -- and they fluctuated similarly, meaning that if one was abundant in a given year, so was the other. And good years, it turns out, are associated with colder seawater temperatures, an unfortunate preference for kelp as ocean temperatures continue to rise.

Understanding how changes in the ocean affect kelp is important because they're what's called a "foundation species," a crucial source of food and habitat for organisms.

"Kelp are a natural feature that generates habitat for hundreds, probably thousands of species of fish, invertebrates and microbes," Pfister said. "They're really a locus for biodiversity along these shores, so it's important to understand how they respond to climate change."

While Cameron's 1915 report delves into the chemistry of potassium salts, nitrogen and fertilizer, it's vague on exactly what the U.S. government wanted do with a new kelp-based source of potash. But given that the world's supply of potash came from an increasingly belligerent German Empire just before World War I broke out, one could read between the lines and look to another industry that sprung up around the same time in California. These outfits focused on harvesting kelp and extracting chemicals from it, one of which, potassium nitrate or saltpeter, is a major ingredient of gunpowder.

Ultimately, kelp never became a major source of potash for the U.S. agricultural industry. Following the war, harvesting kelp for nitrogen became far more costly than a new commercial process invented by Fritz Haber in Germany to pull nitrogen from the atmosphere. For the benefit of the many species that depend upon them, the kelp beds (and the historic maps) remain.

Citation: Catherine A. Pfister, Helen D. Berry & Thomas Mumford; The dynamics of Kelp Forests in the Northeast Pacific Ocean and the relationship with environmental drivers; Journal of Ecology, 2017; DOI: 10.1111/1365-2745.12908.

Contact: Matt Wood
University of Chicago Medical Center

Marine turtles dying after becoming entangled in plastic rubbish

This is a live leatherback turtle entangled in fishing ropes which increases drag, Grenada 2014. Credit: Kate Charles, Ocean Spirits.

Hundreds of marine turtles die every year after becoming entangled in rubbish in the oceans and on beaches, including plastic 'six pack' holders and disgarded fishing gear.

The rise in plastic refuse in the ocean and on beaches is killing turtles of all species, with a disproportionate impact on hatchlings and young turtles, research by the University of Exeter shows.

A world-wide survey covering the major oceans where turtles live found that found that 91 per cent of the entangled turtles were found dead. They also suffered serious wounds from entanglement, leading to maiming, amputation or choking. Others that survived were forced to drag disgarded rubbish or debris with them.

The survey found turtles are being tangled up in lost fishing nets, plastic twine and nylon fishing line, as well as six pack rings from canned drinks, plastic packaging straps, plastic balloon string, kite string, plastic packaging and discarded anchor line and seismic cable. Turtles were also discovered entangled in discarded plastic chairs, wooden crates, weather balloons and boat mooring line.

The research, published in Endangered Species Research, sheds light on the true threat of plastic pollution to marine turtles, which, other research has shown, also eat plastic rubbish, and marine creatures caught up in it.

Professor Brendan Godley. Professor of Conservation Science and Director of the Centre for Ecology & Conservation at the University of Exeter's Penryn campus and the lead author warned that as plastic pollution increases more and more turtles are likely to become entangled.

Mortality from entanglement has increased substantially over the last century, as with marine mammals and birds.

84 per cent of the 106 experts surveyed on the Atlantic, Pacific Caribbean, Mediterranean and Indian ocean coast, who responded said they had found turtles tangled in rubbish, including plastic debris and lost or disgarded fishing gear.

The report concluded that, based on the survey results, that more than 1000 turtles are likely to die due to entanglement. But the figure is likely to be a 'gross underestimation' of the scale of the threat to turtles. Not all dead turtles strand on beaches, especially young animals, and some decay at sea. Some of the experts surveyed said that not all stranded turtles are found and that some are removed by local people to eat.

This is a Drowned Green turtle entangled in ghost nets in Uruguay. Credit: Karumbe.

Hatchlings and young sea turtles are particularly susceptible to getting tangled up in lost or disgarded fishing gear or floating debris. Juvenile turtles ride on ocean currents to zones where floating rubbish and debris is concentrated creating an 'ecological trap'. They also 'set up home' near floating debris and can remain there for years.

Professor Godley, the lead author, said the mortality rate from becoming tangled up in human refuse was, in practice, likely to be far higher than 1,000 turtles a year estimated by the limited survey.

"Plastic rubbish in the oceans, including lost or disgarded fishing gear which is not biodegradable, is a major threat to marine turtles. We found, based on beach strandings, that more than 1000 turtles are dying a year after becoming tangled up, but this is almost certainly a gross underestimate. Young turtles and hatchings are particularly vulnerable to entanglement," he said.

"Experts we surveyed found that entanglement in plastic and other pollution could pose a long term impact on the survival of some turtle populations and is a greater threat to them than oil spills. We need to cut the level of plastic waste and purse biodegradable alternatives if we are to tackle this grave threat to turtles' welfare."

The Exeter University research team, which included two research students Emily Duncan and Zara Botterell who work in conjunction with Plymouth Marine Laboratory, surveyed experts who rescue and rehabilitate stranded turtles in 43 countries, to find out if they had discovered turtles which had been tangled up. They also found 23 reports of entangled turtles in peer-reviewed publications, magazines, newspapers and reports.

All species of turtle were found entangled, but Olive Ridley turtles are the most likely species to get tangled up. The species nests in the hundreds of thousands. It forages in areas where marine debris can aggregate. It may also be attracted to feeding on marine rubbish, including disgarded fishing tackle.

Most entanglements recorded were in lost or discarded fishing gear known as 'ghost fishing' rope, nets and lines. Since the 1950s the fishing industry has replaced natural fibres such as cotton, jute and hemp with synthetic plastic materials such as nylon, polyethylene and polypropylene which doesn't biodegrade in water.

The report concludes: "Entanglement with anthropogenic plastic materials, such as discarded fishing gear, as well as land based sources, is an under reported and under researched threat to marine turtles."

But it points out some communities are actively working to rescue turtles that get tangled up. Fishermen in Sicily volunteer to take part in the rescue of turtles in difficulty at sea and on beaches, and are trained to transfer them to rescue centres.

Citation: Duncan EM, Botterell ZLR, Broderick AC, Galloway TS, Lindeque PK, Nuno A, Godley BJ; REVIEW: A global review of marine turtle entanglement in anthropogenic debris: a baseline for further action; Endangered Species Research Vol. 34: 431-448 (December 11, 2017); DOI: 10.3354/esr00865.

Contact: Marie Woolf
University of Exeter

 

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Study finds ways to avoid hidden dangers of accumulated stresses on seagrass

Hundreds of millions of cubic meters of vital seagrass meadows worldwide can potentially be at risk of collapse from accumulated effects of repeated dredging and natural stress.

QUT Research Fellow Dr. Paul Wu is part of a research team working towards saving seagrass from dredging. Photo by Anthony Weate/QUT Marketing & Communication.

A new QUT-led study has found ways to detect hidden dangers of repeated stresses on seagrass using statistical modelling.

The research, published by the Journal of Applied Ecology, found cumulative maintenance dredging which affected the light on the sea floor increased risks on seagrass survival. It found, globally, seagrass meadows can be at risk of collapse from accumulated effects of repeated dredging and natural stress.

However, lead researcher QUT's Dr Paul Wu said maintenance dredging programs of one or two weeks (common in Queensland) were unlikely to impact seagrass.

• Seagrass provide shelter and food to marine life, including at-risk species like dugongs and green turtles
• Globally, hundreds of millions of cubic metres of sediment are dredged annually
• Dredging repeated every 1, 2 or 3 years, or for three months or more duration, needs careful management to avoid a loss of resilience
• Latest research builds on recently released research pinpointing 'ecological windows' for timing of dredging

"Our model predicts ahead of time how much repeated stress is too much," Dr Wu said. "Our results show dredging can be successfully managed to maintain healthy seagrass meadows in the absence of other disturbances. The research isn't about stopping dredging. It's about being able to predict how resilient the seagrass will be by incorporating environmental conditions such as storms, cyclones and run-off from agriculture." Dr Wu said port authorities and coastal developers could use the research to support a risk-informed management strategy.

 

Coastal development is commonly associated with dredging, which presents a hazard to ecosystem health via stressors including light degradation and water quality reduction.

"Generally, dredging repeated every one, two or three years, or of three months duration or more, needs careful management to avoid a loss of seagrass resilience," Dr Wu said.

Dr Wu said the development of a risk modelling approach, based on a Bayesian Network, was a tool increasingly applied in ecology.

The findings of the study are specific to hazards and environmental conditions for individual sites.

"For instance, dredging repeated every one, two or three years on a Halophila meadow at Hay Point was predicted to be at risk of losing resilience," he said.

"We developed 960 hazard scenarios including frequency of dredging durations of between one to six months and the level of light stress and the month when dredging occurred."

Dr Wu is an Associate Investigator with the ARC Centre of Excellence for Mathematical and Statistical Frontiers (ACEMS) within QUT's Mathematical and Statistical Sciences Faculty.

Citation: Paul Pao-Yen Wu, Kathryn McMahon, Michael A. Rasheed, Gary A. Kendrick, Paul H. York, Kathryn Chartrand, M. Julian Caley, Kerrie Mengersen; Managing seagrass resilience under cumulative dredging affecting light: Predicting risk using dynamic Bayesian networks; Journal of Applied Ecology, 2017; DOI: 10.1111/1365-2664.13037.

Contact: Debra Nowland, Queensland University of Technology

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Molting bowhead whales likely rub on rocks to facilitate sloughing off skin

Example of an animal with nearly no sloughing skin (i.e., proportion of body with sloughing skin = <33%) (A) and another bowhead whale with a high degree of sloughing (>66% of body) and a blotchy skin type (B). Credit: Fortune et al (2017) CC BY

Bowhead whales molt and rub on large rocks -- likely facilitating exfoliation -- in coastal waters in the eastern Canadian Arctic during late summer, according to a study published November 22, 2017 in the open-access journal PLOS ONE by Sarah Fortune from University of British Columbia, Canada, and colleagues.

Most whales, dolphins and porpoises are thought to shed and replace their skin continuously. However, this may not be true of Arctic species -- such as beluga whales, narwhal and bowhead whales -- that seasonally occupy warmer waters such as estuaries and fiords. Beluga whales and likely narwhal molt in estuaries during the summer, where warmer water is hypothesized to facilitate skin turnover by increasing metabolic activities or by providing a physiological cue such as daylight. However, little is known about molting in bowhead whales.

Fortune and colleagues studied molting and behavior of bowhead whales summering in Cumberland Sound, Nunavut, Canada. Data included still photographs of 81 bowhead whales and videos of four bowhead whales.

The still images showed that all of the bowhead whales studied were molting, and that nearly 40 percent of them had mottled skin over much of their bodies (more than two-thirds). The videos captured bowhead whales rubbing on large rocks in shallow coastal areas. Both molting and rock rubbing appeared to be pervasive among bowhead whales during late summer in the study area.

This work supports the hypothesis that warmer water may facilitate molting, and suggests that rock-rubbing facilitates exfoliation. Moreover, the researchers speculate that bowhead whales may molt to shed parasites such as whale lice or to shed skin that has been damaged by the sun. The latter could reduce the risk of ultraviolet radiation during the summer at high latitudes, which could be important for long-lived species such as bowhead whales because skin damage accumulates with age.

Citation: Fortune SME, Koski WR, Higdon JW, Trites AW, Baumgartner MF, Ferguson SH (2017); Evidence of molting and the function of "rock-nosing" behavior in bowhead whales in the eastern Canadian Arctic; PLoS ONE 12(11): e0186156. https://doi.org/10.1371/journal.pone.0186156.