RESEARCHERS SAY OCEAN WARMING WILL LEAD TO MARINE ANIMAL MIGRATION

FROM:  NATIONAL SCIENCE FOUNDATION
Warmer, lower-oxygen oceans will shift marine habitats

Changes will result in marine animals moving away from equator
Modern mountain climbers usually carry tanks of oxygen to help them reach the summit. The combination of physical exertion and lack of oxygen at high altitudes creates a major challenge for mountaineers.

Now, just in time for World Oceans Day on Monday, June 8, researchers have found that the same principle applies to marine species during climate change.

Warmer water temperatures will speed up the animals' metabolic need for oxygen, as also happens during exercise, but the warmer water will hold less of the oxygen needed to fuel their bodies, similar to what happens at high altitudes.

Results of the study are published in this week's issue of the journal Science.

"This work is important because it links metabolic constraints to changes in marine temperatures and oxygen supply," said Irwin Forseth, program director in the National Science Foundation's (NSF) Division of Integrative Organismal Systems, which funded the research along with NSF's Division of Ocean Sciences.

"Understanding connections such as this is essential to allow us to predict the effects of environmental changes on the distribution and diversity of marine life.”

Marine animals pushed away from equator

The scientists found that these changes will act to push marine animals away from the equator. About two thirds of the respiratory stress due to climate change is caused by warmer temperatures, while the rest is because warmer water holds less dissolved gases such as oxygen.

"If your metabolism goes up, you need more food and you need more oxygen," said lead paper author Curtis Deutsch of the University of Washington.

"Aquatic animals could become oxygen-starved in a warmer future, even if oxygen doesn't change. We know that oxygen levels in the ocean are going down now and will decrease more with climate warming."

Four Atlantic Ocean species studied

The study centered on four Atlantic Ocean species whose temperature and oxygen requirements are well known from lab tests: Atlantic cod in the open ocean; Atlantic rock crab in coastal waters; sharp snout seabream in the sub-tropical Atlantic; and common eelpout, a bottom-dwelling fish in shallow waters in high northern latitudes.

Deutsch and colleagues used climate models to see how projected temperature and oxygen levels by 2100 would affect the four species ability to meet their future energy needs.

The near-surface ocean is projected to warm by several degrees Celsius by the end of this century. Seawater at that temperature would hold 5-10 percent less oxygen than it does now.

Results show that future rock crab habitat, for example, would be restricted to shallower water, hugging the more oxygenated surface.

Equatorial part of animals' ranges uninhabitable

For all four species, the equatorial part of their ranges would become uninhabitable because peak oxygen demand would be greater than the supply.

Viable habitats would shift away from the equator, displacing from 14 percent to 26 percent of the current ranges.

The authors believe the results are relevant for all marine species that rely on aquatic oxygen as an energy source.

"The Atlantic Ocean is relatively well-oxygenated," Deutsch said. "If there's oxygen restriction in the Atlantic Ocean marine habitat, then it should be everywhere."

Climate models predict that the northern Pacific Ocean's relatively low oxygen levels will decline even more, making it the most vulnerable part of the seas to habitat loss.

"For aquatic animals that are breathing water, warming temperatures create a problem of limited oxygen supply versus higher demand," said co-author Raymond Huey, a University of Washington biologist who has studied metabolism in land animals and in human mountain climbers.

"This simple metabolic index seems to correlate with the current distributions of marine organisms," he said. "That means that it gives us the power to predict how range limits are going to shift with warming."

A day-to-day "dead zone"

Previously, marine scientists thought about oxygen more in terms of extreme events that could cause regional die-offs of marine animals, also known as dead zones.

"We found that oxygen is also a day-to-day restriction on where species will live," Deutsch said.

"The effect we're describing will be part of what's pushing species around in the future."

Other co-authors are Hans Otto-Portner of the Alfred Wegener Institute in Germany; Aaron Ferrel of the University of California, Los Angeles; and Brad Seibel at the University of Rhode Island.

The Gordon and Betty Moore Foundation and the Alfred Wegener Institute also funded the research.

-NSF-
Media Contacts
Cheryl Dybas, NSF

PLANKTON BLOOM FINDS WAY TO MOVE DOWN

FROM:  NATIONAL SCIENCE FOUNDATION
Spring plankton bloom hitches ride to sea's depths on ocean eddies

Eddies--whirlpools within currents--transport plankton downward from the ocean surface
Just as crocus and daffodil blossoms signal the start of a warmer season on land, a similar "greening" event--a massive bloom of microscopic plants, or phytoplankton--unfolds each spring in the North Atlantic Ocean from Bermuda to the Arctic.

Fertilized by nutrients that have built up during the winter, the cool waters of the North Atlantic come alive every spring and summer with a vivid display of color that stretches across hundreds and hundreds of miles.

North Atlantic Bloom turns ocean into sea of plankton

In what's known as the North Atlantic Bloom, millions of phytoplankton use sunlight and carbon dioxide (CO2) to grow and reproduce at the ocean's surface.

During photosynthesis, phytoplankton remove carbon dioxide from seawater and release oxygen as a by-product. That allows the oceans to absorb additional carbon dioxide from the atmosphere. If there were fewer phytoplankton, atmospheric carbon dioxide would increase.

Flowers ultimately wither and fade, but what eventually happens to these tiny plants produced in the sea? When phytoplankton die, the carbon in their cells sinks to the deep ocean.

Plankton integral part of oceanic "biological pump"

This so-called biological pump makes the North Atlantic Ocean efficient at soaking up CO2 from the air.

"Much of this 'particulate organic carbon,' especially the larger, heavier particles, sinks," says scientist Melissa Omand of the University of Rhode Island, co-author of a paper on the North Atlantic Bloom published today in the journal Science.

"But we wanted to find out what's happening to the smaller, non-sinking phytoplankton cells from the bloom. Understanding the dynamics of the bloom and what happens to the carbon produced by it is important, especially for being able to predict how the oceans will affect atmospheric CO2 and ultimately climate."

In addition to Omand, other authors of the paper are Amala Mahadevan of the Woods Hole Oceanographic Institution, Eric D'Asaro and Craig Lee of the University of Washington, and Mary Jane Perry, Nathan Briggs and Ivona Cetinic of the University of Maine.

The research was funded by the National Science Foundation (NSF).

"It's been a challenge to estimate carbon export from the ocean's surface waters to its depths based on measurements of properties such as phytoplankton carbon," says David Garrison, program director in NSF's Division of Ocean Sciences. "This paper describes a mechanism for doing that."

Tracking a bloom: Floats, gliders and other instruments

During fieldwork from the research vessels Bjarni Saemundsson and Knorr, the scientists used a float to follow a patch of seawater off Iceland. They observed the progression of the bloom by taking measurements from multiple platforms.

Autonomous gliders outfitted with sensors were used to gather data such as temperature, salinity and information about the chemistry and biology of the bloom--oxygen, nitrate, chlorophyll and the optical signatures of the particulate matter.

At the onset of the bloom and over the next month, four teardrop-shaped seagliders gathered 774 profiles to depths of up to 1,000 meters (3,281 feet).

Analysis of the profiles showed that about 10 percent had unusually high concentrations of phytoplankton bloom properties, even in deep waters, as well as high oxygen concentrations usually found at the surface.

"These profiles were showing what we initially described as 'bumps' at depths much deeper than phytoplankton can grow," says Omand.

Staircases to the deep: Ocean eddies

Using information collected at sea by Perry, D'Asaro and Lee, Mahadevan modeled ocean currents and eddies ("whirlpools" within currents) and their effects on the spring bloom.

"What we were seeing was surface water, rich with phytoplankton carbon, being transported downward by currents on the edges of eddies," Mahadevan says.

"Eddies hadn't been thought of as a major way organic matter is moved into the deeper ocean. But this type of eddy-driven 'subduction' could account for a significant downward movement of phytoplankton from the bloom."

In related work published in Science in 2012, the researchers found that eddies act as early triggers of the North Atlantic Bloom.

Eddies help keep phytoplankton in shallower water where they can be exposed to sunlight to fuel photosynthesis and growth.

Next, the scientists hope to quantify the transport of organic matter from the ocean's surface to its depths in regions beyond the North Atlantic and at other times of year and relate that to phytoplankton productivity.

Learning more about eddies and their link with plankton blooms will allow for more accurate global models of the ocean's carbon cycle, the researchers say, and improve the models' predictive capabilities.

-NSF-
Media Contacts
Cheryl Dybas, NSF

VIRUSES IN THE DEEP

FROM:  NATIONAL SCIENCE FOUNDATION
The 'intraterrestrials': New viruses discovered in ocean depths

Viruses infect methane-eating archaea beneath the seafloor
The intraterrestrials, they might be called.

Strange creatures live in the deep sea, but few are odder than the viruses that inhabit deep ocean methane seeps and prey on single-celled microorganisms called archaea.

The least understood of life's three primary domains, archaea thrive in the most extreme environments on the planet: near hot ocean rift vents, in acid mine drainage, in the saltiest of evaporation ponds and in petroleum deposits deep underground.

Virus in the deep blue sea

While searching the ocean's depths for evidence of viruses, scientists have found a remarkable new one, a virus that seemingly infects archaea that live beneath the ocean floor.

The researchers were surprised to discover that the virus selectively targets one of its own genes for mutation, and that this capacity is also shared by archaea themselves.

The findings appear today in a paper in the journal Nature Communications.

The project was supported by a National Science Foundation (NSF) Dimensions of Biodiversity grant to characterize microbial diversity in methane seep ecosystems. Dimensions of Biodiversity is supported by NSF's Directorates for Biological Sciences and Geosciences.

New information about life in ocean depths

"Life far beneath the Earth's subsurface is an enigma," said Matt Kane, program director in NSF's Division of Environmental Biology. "By probing deep into our planet, these scientists have discovered new information about Earth's microbes and how they evolve."

"Our study uncovers mechanisms by which viruses and archaea can adapt in this hostile environment," said David Valentine, a geoscientist at the University of California Santa Barbara (UCSB) and co-author of the paper.

The results, he said, raise new questions about the evolution and interaction of the microbes that call the planet's interior home.

"It's now thought that there's more biomass inside the Earth than anywhere else, just living very slowly in this dark, energy-limited environment," said paper co-author Sarah Bagby of UCSB.

Using the submersible Alvin, Valentine and colleagues collected samples from a deep-ocean methane seep by pushing tubes into the ocean floor and retrieving sediments.

The contents were brought back to the lab and fed methane gas, helping the methane-eating archaea in the samples to grow.

When the team assayed the samples for viral infection, they discovered a new virus with a distinctive genetic fingerprint that suggested its likely host was methane-eating archaea.

Genetic sequence of new virus holds the key

The researchers used the genetic sequence of the new virus to chart other occurrences in global databases.

"We found a partial genetic match from methane seeps off Norway and California," said lead author Blair Paul of UCSB. "The evidence suggests that this viral type is distributed around the globe in deep ocean methane seeps."

Further investigation revealed another unexpected finding: a small genetic element, known as a diversity-generating retroelement, that accelerates mutation of a specific section of the virus's genome.

Such elements had been previously identified in bacteria and their viruses, but never among archaea or the viruses that infect them.

"These researchers have shown that cutting-edge genomic approaches can help us understand how microbes function in remote and poorly known environments such as ocean depths," said David Garrison, program director in NSF's Division of Ocean Sciences.

While the self-guided mutation element in the archaea virus resembles known bacterial elements, the researchers found that it has a divergent evolutionary history.

"The target of guided mutation--the tips of the virus that make first contact when infecting a cell--is similar," said Paul.

"But the ability to mutate those tips is an offensive countermeasure against the cell's defenses, a move that resembles a molecular arms race."

Unusual genetic adaptations

Having found guided mutation in a virus-infecting archaea, the scientists reasoned that archaea themselves might use the same mechanism for genetic adaptation.

In an exhaustive search, they identified parallel features in the genomes of a subterranean group of archaea known as nanoarchaea.

Unlike the deep-ocean virus that uses guided mutation to alter a single gene, the nanoarchaea target at least four distinct genes.

"It's a new record," said Bagby.

"Bacteria had been observed to target two genes with this mechanism. That may not seem like a huge difference, but targeting four is extraordinary."

According to Valentine, the genetic mutation that fosters these potential variations may be key to the survival of archaea beneath the Earth's surface.

"The cell is choosing to modify certain proteins," he said. "It's doing its own protein engineering. While we don't yet know what those proteins are being used for, learning about the process can tell us something about the environment in which these organisms thrive."

Viral DNA sequencing was provided through a Gordon and Betty Moore Foundation grant. The research team also included scientists from the University of California, Los Angeles; the University of California, San Diego; and the U.S. Department of Energy's Joint Genome Institute.

-NSF-
Media Contacts
Cheryl Dybas, NSF

LIFE BENEATH THE SEAFLOOR

FROM:  NATIONAL SCIENCE FOUNDATION
No limit to life in deep sediment of ocean's "deadest" region

Marine scientists find microbes from seafloor to igneous basement below
"Who in his wildest dreams could have imagined that, beneath the crust of our Earth, there could exist a real ocean...a sea that has given shelter to species unknown?"

So wrote Jules Verne almost 150 years ago in A Journey to the Center of the Earth.

He was correct: Ocean deeps are anything but dead.

Now, scientists have found oxygen and oxygen-breathing microbes all the way through the sediment from the seafloor to the igneous basement at seven sites in the South Pacific gyre, considered the "deadest" location in the ocean.

Findings contrast with previous studies

Their findings contrast with previous discoveries that oxygen was absent from all but the top few millimeters to decimeters of sediment in biologically productive regions of the ocean.

The results are published today in a paper in the journal Nature Geoscience.

"Our objective was to understand the microbial community and microbial habitability of sediment in the deadest part of the ocean," said scientist Steven D'Hondt of the University of Rhode Island Graduate School of Oceanography, lead author of the paper.

"Our results overturn a 60-year-old conclusion that the depth limit to life is in the sediment just meters below the seafloor in such regions.

"We found that there is no limit to life in this sediment. Oxygen and aerobic microbes hang in there all the way to the igneous basement, to at least 75 meters below the seafloor."

Under the seafloor, life all the way down

Based on the researchers' predictive model and core samples they collected in 2010 from the research drillship JOIDES Resolution, they believe that oxygen and aerobic microbes occur throughout the sediment in up to 37 percent of the world's oceans and 44 percent of the Pacific Ocean.

They found that the best indicators of oxygen penetration to the igneous basement are a low sedimentation accumulation rate and a relatively thin sediment layer.

Sediment accumulates at just a few decimeters to meters per million years in the regions where the core samples were collected.

In the remaining 63 percent of the ocean, most of the sediment beneath the seafloor is expected to lack dissolved oxygen and to contain anaerobic communities.

While the researchers found evidence of life throughout the sediment, they did not detect a great deal of it.

Life in the slow lane

The team found extremely slow rates of respiration and approximately 1,000 cells per cubic centimeter of subseafloor sediment in the South Pacific gyre--rates and quantities that had been nearly undetectable.

"It's really hard to find life when it's not very active and is in extremely low concentrations," said D'Hondt.

According to D'Hondt and co-author Fumio Inagaki of the Japan Agency for Marine-Earth Science and Technology, the discovery of oxygen throughout the sediment may have significant implications for Earth's chemical evolution.

The oxidized sediment is likely carried into the mantle at subduction zones, regions of the seafloor where tectonic plates collide, forcing one plate beneath the other.

"Subduction of these big regions where oxygen penetrates through the sediment and into the igneous basement introduces oxidized minerals to the mantle, which may affect the chemistry of the upper mantle and the long-term evolution of Earth's surface oxidation," D'Hondt said.

Holistic approach to study of subseafloor biosphere

The principal research funders were the U.S. National Science Foundation (NSF) and Japan's Ministry of Education, Culture, Sports, Science and Technology.

"We take a holistic approach to the subseafloor biosphere," said Rick Murray, co-author of the paper. Murray is on leave from Boston University, currently serving as director of the NSF Division of Ocean Sciences.

"Our team includes microbiologists, geochemists, sedimentologists, physical properties specialists and others--a hallmark of interdisciplinary research."

The research involved 35 scientists from 12 countries.

The project is part of the NSF-funded Center for Dark Energy Biosphere Investigations (C-DEBI), which explores life beneath the seafloor.

The research is also part of the Deep Carbon Observatory, a decade-long international science initiative to investigate the 90 percent of Earth's carbon located deep inside the planet.

The Nature Geoscience paper is available online.

-NSF-

NSF VIDEO: SEA SPRAY: COMPLEX CHEMISTRY WITH BIG EFFECTS ON CLIMATE-SCIENCE NATION

SCIENTIST SAYS DEEPWATER HORIZON OIL LOCATED

FROM:  NATIONAL SCIENCE FOUNDATION 

Where did the Deepwater Horizon oil go? To Davy Jones' Locker at the bottom of the sea

New analysis traces oil to its resting place on the Gulf of Mexico sea floor
Where's the remaining oil from the 2010 Deepwater Horizon disaster in the Gulf of Mexico?

The location of 2 million barrels of oil thought to be trapped in the deep ocean has remained a mystery. Until now.

Scientist David Valentine of the University of California, Santa Barbara (UCSB) and colleagues from the Woods Hole Oceanographic Institution (WHOI) and the University of California, Irvine, have discovered the path the oil followed to its resting place on the Gulf of Mexico sea floor.

The findings appear today in the journal Proceedings of the National Academy of Sciences.

"This analysis provides us with, for the first time, some closure on the question, 'Where did the oil go and how did it get there?'" said Don Rice, program director in the National Science Foundation's (NSF) Division of Ocean Sciences, which funded the research along with NSF's Division of Earth Sciences.

"It also alerts us that this knowledge remains largely provisional until we can fully account for the remaining 70 percent."

For the study, the scientists used data from the Natural Resource Damage Assessment conducted by the National Oceanic and Atmospheric Administration.

The U.S. government estimates the Macondo Well's total discharge--from April until the well was capped in July--at 5 million barrels.

By analyzing data from more than 3,000 samples collected at 534 locations over 12 expeditions, the researchers identified a 1,250-square-mile patch of the sea floor on which four to 31 percent of the oil trapped in the deep ocean was deposited. That's the equivalent of 2 to 16 percent of the total oil discharged during the accident.

The fallout of oil created thin deposits that are most extensive to the southwest of the Macondo Well. The oil is concentrated in the top half-inch of the sea floor and is patchily distributed.

The investigation focused primarily on hopane, a nonreactive hydrocarbon that served as a proxy for the discharged oil.

The researchers analyzed the distribution of hopane in the northern Gulf of Mexico and found that it was concentrated in a thin layer at the sea floor within 25 miles of the ruptured well, clearly implicating Deepwater Horizon as the source.

"Based on the evidence, our findings suggest that these deposits are from Macondo oil that was first suspended in the deep ocean, then settled to the sea floor without ever reaching the ocean surface," said Valentine, a biogeochemist at UCSB.

"The pattern is like a shadow of the tiny oil droplets that were initially trapped at ocean depths around 3,500 feet and pushed around by the deep currents.

"Some combination of chemistry, biology and physics ultimately caused those droplets to rain down another 1,000 feet to rest on the sea floor."

Valentine and colleagues were able to identify hotspots of oil fallout in close proximity to damaged deep-sea corals.

According to the researchers, the data support the previously disputed finding that these corals were damaged by the Deepwater Horizon spill.

"The evidence is becoming clear that oily particles were raining down around these deep sea corals, which provides a compelling explanation for the injury they suffered," said Valentine.

"The pattern of contamination we observe is fully consistent with the Deepwater Horizon event but not with natural seeps--the suggested alternative."

While the study examined a specified area, the scientists argue that that the observed oil represents a minimum value. They believe that oil deposition likely occurred outside the study area but so far has largely evaded detection because of its patchiness.

"These findings," said Valentine, "should be useful for assessing the damage caused by the Deepwater Horizon spill, as well as planning future studies to further define the extent and nature of the contamination.

"Our work can also help assess the fate of reactive hydrocarbons, test models of oil's behavior in the ocean, and plan for future spills."

Co-authors of the paper are G. Burch Fisher and Sarah C. Bagby of UCSB; Robert K. Nelson, Christopher M. Reddy and Sean P. Sylva of WHOI and Mary A. Woo of University of California, Irvine.

-NSF-

A MEASURE OF OCEAN PROTEINS MAY REVEAL HOW OCEAN SYSTEMS OPERATE

FROM:  THE NATIONAL SCIENCE FOUNDATION 

Scientists apply biomedical technique to reveal changes in body of the ocean
Researchers look at biochemical reactions happening inside ocean organisms
For decades, doctors have developed methods to diagnose how different types of cells and systems in the body are functioning. Now scientists have adapted an emerging biomedical technique to study the vast body of the ocean.

In a paper published in the journal Science, scientists demonstrate that they can identify and measure proteins in the ocean, revealing how single-celled marine organisms and ocean ecosystems operate.

The National Science Foundation (NSF) and the Gordon and Betty Moore Foundation funded the research.

"Proteins are the molecules that catalyze the biochemical reactions happening in organisms," says Woods Hole Oceanographic Institution (WHOI) biogeochemist Mak Saito, the paper's lead author.

"Instead of just measuring what species are in the ocean, now we can look inside those organisms and see what biochemical reactions they're performing in the face of various ocean conditions.

"It's a potentially powerful tool we can use to reveal the inner biochemical workings of organisms in ocean ecosystems--and to start diagnosing how the oceans are responding to pollution, climate change and other shifts."

The emerging biomedical technique of measuring proteins--a field called proteomics--builds on the more familiar field of genomics that has allowed scientists to detect and identify genes in cells.

"Proteomics is an advanced diagnostic tool that allows us to take the pulse of, for example, phytoplankton cells while they respond to environmental cues," says paper co-author Anton Post, currently on leave from the Marine Biological Laboratory in Woods Hole, Mass., and a program officer in NSF's Division of Ocean Sciences.

The new study is an initial demonstration that proteomic techniques can be applied to marine species not only to identify the presence of proteins, but for the first time, to precisely count their numbers.

"We're leveraging that biomedical technology and translating it for use in the oceans," Saito says.

"Just as you'd analyze proteins in a blood test to get information on what's happening inside your body, proteomics gives us a new way to learn what's happening in ocean ecosystems, especially under multiple stresses and over large regions.

"With that information, we can identify changes, assess their effects on society and devise strategies to adapt."

For their study, the scientists collected water samples during a research cruise along a 2,500-mile stretch of the Pacific Ocean from Hawaii to Samoa.

The transect cut across regions with widely different concentrations of nutrients, from areas rich in iron to the north to areas near the equator that are rich in phosphorus and nitrogen but devoid of iron.

Back in the lab, the scientists analyzed the samples, focusing on proteins produced by one of the ocean's most abundant microbes, Prochlorococcus.

They used mass spectrometers to separate individual proteins in the samples, identifying them by their peptide sequences.

In subsequent steps, the scientists demonstrated for the first time that they could precisely measure the amounts of specific proteins in individual species at various locations in the ocean.

The results painted a picture of what factors were controlling microbial photosynthesis and growth and how the microbes were responding to different conditions over a large geographic region of the sea.

For example, in areas where nitrogen was limited, the scientists found high levels of a protein that transports urea, a form of nitrogen, which the microbes used to maximize their ability to obtain the essential nutrient.

In areas where iron was deficient, they found an abundance of proteins that help grab and transport iron.

"The microbes have biochemical systems that are ready to turn on to deal with low-nutrient situations," Saito says.

In areas in-between, where the microbes were starved for both nutrients, proteins indicated which biochemical machinery the microbes used to negotiate multiple environmental stresses.

The protein measurements enabled the scientists to map when, where, and how ecosystem changes occurred over broad areas of the ocean.

"We measured about 20 biomarkers that indicate metabolism, but we can scale up that capacity to measure many more simultaneously," Saito says.

"We're building an oceanic proteomic capability, which includes sampling with ocean-going robots, to allow us to diagnose the inner workings of ocean ecosystems and understand how they respond to global change."

Along with Saito and Post, the research team included Matthew McIlvin, Dawn Moran, Tyler Goepfert and Carl Lamborg of WHOI and Giacomo DiTullio of the College of Charleston in South Carolina.

-NSF-

SCIENTISTS STUDY CHANGES IN MERCURY LEVELS IN OCEANS

FROM:  NATIONAL SCIENCE FOUNDATION 

Mercury in the world's oceans: On the rise

New results show three times as much in upper oceans since Industrial Revolution times

Little was known about how much mercury in the environment was the result of human activities, or how much "bioavailable" mercury was in the world's oceans. Until now.

The first direct calculation of mercury pollution in the world's oceans, based on data from 12 oceanographic sampling cruises during the last eight years, is reported in this week's issue of the journal Nature.

The scientists involved are affiliated with the Woods Hole Oceanographic Institution (WHOI) in Massachusetts, Wright State University in Ohio, the Observatoire Midi-Pyréneés in France and the Royal Netherlands Institute for Sea Research in the Netherlands.

The research was funded by the National Science Foundation (NSF) and the European Research Council. It was led by WHOI marine chemist Carl Lamborg. The results offer a look at the global distribution of mercury in the marine environment.

"Mercury is an environmental poison that's detectable wherever we look for it, including the ocean abyss," says Don Rice, director of the NSF's Chemical Oceanography Program.

"These scientists have reminded us that the problem is far from abatement, especially in regions of the world's oceans where the human fingerprint is most distinct."

Mercury is a naturally occurring element as well as a by-product of such human activities as burning coal and making cement.

"If we want to regulate mercury emissions into the environment and in the food we eat, we should first know how much is there and how much human activity is adding every year," says Lamborg.

"At the moment, however, there is no way to look at a water sample and tell the difference between mercury that came from pollution and mercury that came from natural sources. Now we at least have a way to separate the bulk contributions of natural and human sources over time."

The group started by looking at data that reveal details about ocean levels of phosphate, a substance that is better studied in the oceans than mercury and that behaves in much the same way as mercury.

Phosphate is a nutrient that, like mercury, is taken up into the marine food web by binding with organic material.

By determining the ratio of phosphate-to-mercury in water deeper than 1,000 meters (3,300 feet) that has not been in contact with Earth's atmosphere since the Industrial Revolution, the researchers were able to estimate mercury in the oceans that originated from natural sources such as the breakdown, or weathering, of rocks on land.

Their findings agreed with what they would expect to see given the pattern of global ocean circulation.

North Atlantic waters, for example, showed the most obvious signs of mercury pollution because that's where surface waters sink to form deep and intermediate water flows.

The tropical and Northeast Pacific, on the other hand, were relatively unaffected; it takes centuries for deep ocean water to circulate to these regions.

Determining the contribution of mercury from human activity required another step.

To obtain estimates for shallower waters and to provide numbers for the amount of mercury in the oceans, the scientists needed a tracer--a substance that could be linked with major human activities that release mercury into the environment.

They found it in one of the most well-studied gases of the past 40 years: carbon dioxide. Databases containing information on carbon dioxide in ocean waters are extensive and readily available for every ocean at all depths.

Because much of the mercury and carbon dioxide from human sources comes from the same activities, the team was able to derive with an index relating the two.

The results show that the oceans contain about 60,000 to 80,000 tons of mercury pollution.

Ocean waters shallower than about 100 meters (300 feet) have tripled in mercury concentration since the Industrial Revolution. Mercury in the oceans as a whole has increased roughly 10 percent over pre-industrial times.

"The next 50 years could very well add the same amount we've seen in the past 150," says Lamborg.

"We don't know what that means for fish and marine mammals, but likely that some fish contain at least three times more mercury than 150 years ago. It could be more.

"The key is that now we have some solid numbers on which to base continued work."

-NSF-

Media Contacts
Cheryl Dybas, NSF

OVERFISHING AND CORAL KILLING-SPONGES

FROM:  NATIONAL SCIENCE FOUNDATION 
Overfishing of Caribbean coral reefs favors coral-killing sponges
Caribbean-wide study shows protected coral reefs dominated by sponges with chemical defenses

Scientists had already demonstrated that overfishing removes angelfish and parrotfish that feed on sponges growing on coral reefs--sponges that sometimes smother the reefs. That research was conducted off Key Largo, Fla.

Now, new research by the same team of ecologists suggests that removing these predators by overfishing alters sponge communities across the Caribbean.

Results of the research, by Joseph Pawlik and Tse-Lynn Loh of the University of North Carolina Wilmington, are published this week in the journal Proceedings of the National Academy of Sciences (PNAS).

"In fact," says Pawlik, "healthy coral reefs need predatory fish--they keep sponge growth down."

The biologists studied 109 species of sponges at 69 Caribbean sites; the 10 most common species made up 51 percent of the sponge cover on the reefs.

"Sponges are now the main habitat-forming organisms on Caribbean coral reefs," says Pawlik.

Reefs in the Cayman Islands and Bonaire--designated as off-limits to fishing--mostly have slow-growing sponges that manufacture chemicals that taste bad to predatory fish.

Fish numbers are higher near these reefs. Predatory fish there feast on fast-growing, "chemically undefended" sponges. What's left? Only bad-tasting, but slow-growing, sponges.

Overfished reefs, such as those off Jamaica and Martinique, are dominated by fast-growing, better-tasting sponges. "The problem," says Pawlik, "is that there are too few fish around to eat them." So the sponges quickly take over the reefs.

"It's been a challenge for marine ecologists to show how chemical defenses influence the structure of ocean communities," says David Garrison, a program director in the National Science Foundation's (NSF) Division of Ocean Sciences, which funded the research.

"With this clever study, Pawlik and Loh demonstrate that having--or not having--chemical defenses structures sponge communities on Caribbean coral reefs."

The results support the need for marine protected areas to aid in coral reef recovery, believes Pawlik.

"Overfishing of Caribbean coral reefs, particularly by fish trapping, removes sponge predators," write Loh and Pawlik in their paper. "It's likely to result in greater competition for space between faster-growing palatable sponges and endangered reef-building corals."

The researchers also identified "the bad-tasting molecule used by the most common chemically-defended sponge species," says Pawlik. "It's a compound named fistularin 3."

Similar chemical compounds defend some plants from insects or grazers (deer, for example) in onshore ecosystems, "but the complexity of those ecosystems makes it difficult to detect the advantage of chemical defenses across large areas," says Pawlik.

When it comes to sponges, the view of what's happening is more direct, he says. "The possibility of being eaten by a fish may be the only thing a reef sponge has to worry about."

And what happens to reef sponges may be critical to the future of the Caribbean's corals.

-NSF-

BOUYS RELEASED TO INCREASE ACCURACY OF WEATHER FORCASTS



130528-N-HA376-137 PACIFIC OCEAN (May 28, 2013) Lt. j.g. Jeffrey Grabon launches a global drifter buoy into the Pacific Ocean from the amphibious dock landing ship USS Pearl Harbor (LSD 52) while underway for Pacific Partnership 2013. The buoy, belonging to the UCSD Scripps Institution of Oceanography, is used to measure ocean currents up to 15 meters in depth, sea surface temperatures, and atmospheric pressure. Pacific Partnership is the largest disaster response-preparation mission in the Indo-Asia-Pacific region. (U.S. Navy photo by Mass Communication Specialist 1st Class Lowell Whitman/Released)

FROM: U.S. NAVY
Global Drifter Buoys Released in Pacific Ocean
By Mass Communication Specialist Seaman Samantha J. Webb

PACIFIC OCEAN (NNS) -- Sailors from the office of Naval Meteorology and Oceanography released ten global drifter buoys belonging to the University of California, San Diego Scripps Institution of Oceanography from the amphibious dock landing ship USS Pearl Harbor (LSD 52), May 28, during Pacific Partnership 2013.

The buoys measure ocean currents up to 15 meters in depth, sea surface temperatures and atmospheric pressure. All are important elements in creating an observation network, allowing for more accurate weather forecasts.

"The mission of Pacific Partnership is disaster relief preparedness," said Lt.j.g. Jeffrey S. Grabon, Pacific Partnership Mobile Environment Team division officer. "Most of the disasters that are going on in this region are from typhoons and tsunamis, so if we have observations that we can use to help forecast typhoons, that benefits the area."

The buoys were deployed at specific coordinates while USS Pearl Harbor transited the Pacific Ocean to Samoa, the first mission port of Pacific Partnership.

Both Scripps and the Navy seek to benefit from the buoy drop and subsequent data to be collected.

The global drifter buoys provide real-time data in support of both civilian and DoD activities. That data can be used to improve forecasts, which can benefit the effectiveness of activities like search and rescue missions and disaster response operations.

"I think it is absolutely crucial we have the ability to engage with the U.S. Navy and work in a synergistic way to collect useful data and create deployment opportunities in regions that are hard to access with commercial and scientific vessels," said Luca Centurioni, scientist, Scripps physical oceanography research division. "We really welcome the opportunity to work together with the U.S. Navy 3rd Fleet. "

Grabon said that much of the ongoing research has the potential to impact the Navy.

"Because the Navy is a sea-going, war-fighting force, the better the universities understand the ocean, the better the Navy will understand it," said Grabon.

Pacific Partnership is about bringing people together. The collaboration of the University of California, San Diego Scripps Institute of Oceanography and the United States Navy demonstrates a cooperative approach to both disaster preparedness and prevention by working to understand the many variables that contribute to the long history of natural disasters that have earned the whole region the moniker, "The Pacific Ring of Fire."