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-

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Cheryl Dybas, NSF

DEEPWATER HORIZON OIL SHEEN SOURCE IDENTIFIED

Oil Sheen.  Credit:  NOAA

FROM: NATIONAL SCIENCE FOUNDATION

Study Identifies Source of Oil Sheens Near Deepwater Horizon Site

A chemical analysis indicates that the source of oil sheens recently found floating at the ocean's surface near the site of the Gulf of Mexico Deepwater Horizon oil spill is pockets of oil trapped within the wreckage of the sunken rig.


First reported to the U.S. Coast Guard by multinational oil and gas company BP in September 2012, the oil sheens raised public concern that the Macondo well, which was capped in July 2010, might be leaking.

However, both the Macondo well and the natural oil seeps common to the Gulf of Mexico were confidently ruled out, according to researchers from the University of California Santa Barbara (UCSB) and the Woods Hole Oceanographic Institution (WHOI).

The results are published this week in the journal Environmental Science & Technology.

"Silver linings in the dark cloud of the Deepwater Horizon spill are very hard to come by," says Don Rice, program director in the National Science Foundation's (NSF) Division of Ocean Sciences, which funded the research.

"Among the precious few are the lessons we've learned about the marine biogeochemistry of petroleum mixtures. This team has demonstrated convincingly that we can also use what we have learned for forensic purposes."

The researchers used a recently patented method to fingerprint the chemical makeup of the oil sheens, and to estimate the location of the source based on the extent to which gasoline-like compounds evaporated from the sheens.

"The results demonstrate a recently developed geochemical analytical method and may have real-world implications in environmental management strategies for future contamination incidents," says Deborah Aruguete, program director in NSF's Division of Earth Sciences, which co-funded the research.

Because every oil sample contains chemical clues pointing to the reservoir it came from, scientists can compare it to other samples to determine if they share a common source.

"This appears to be a slow leak from the wreckage of the rig, not another catastrophic discharge from a deep oil reservoir," says geochemist David Valentine of UCSB.

"Continued oil discharge to the Gulf of Mexico from the wreckage of the Deepwater Horizon rig is not a good thing, but there is some comfort that the amount of leakage is limited to the pockets of oil trapped within the wreckage of the rig."

Valentine and WHOI's Chris Reddy have worked on Deepwater Horizon for much of the last three years, investigating a wide range of problems, including the composition of the oil, detection of subsurface plumes, the biodegradation of the oil, the fate of the dispersants and the chemical transition from floating oil slicks to sunken tar balls.

"Because of our ongoing funding from NSF, we were prepared to interrogate the source of mysterious oil sheens in the Gulf of Mexico," said Valentine.

"We've been exploring new ways to do this for several years in the context of natural seeps, and this event provided us an opportunity to apply our fundamental advances to a real-world problem."

The scientists analyzed 14 sheen samples skimmed from the sea surface during two trips to the Gulf of Mexico.

Using comprehensive two-dimensional gas chromatography, a technique developed in Reddy's lab, the researchers first confirmed that the sheens contained oil from the Macondo well.

But the sheen samples also contained trace amounts of olefins, industrial chemicals used in drilling operations. The presence of olefins provided a fingerprint for the sheens the scientists could compare to the samples they had analyzed during the last three years.

Olefins are not found in crude oil and their uniform distribution in the sheens indicated that the Macondo well was unlikely to be the source.

The team surmised that the sheens must be coming from equipment exposed to olefins during drilling operations.

"The occurrence of these man-made olefins in all our sheen samples points to a single main source, which contains both Macondo oil and lesser amounts of the drilling fluids that harbor the olefins," said Valentine.

"This pointed us to the wreckage of the rig, which was known to have both, as the most likely source for the sheens."

The researchers compared the sheen samples to other field samples, some of which they expected would contain olefins and some they thought would not.

The reference samples included two pieces of debris from the Deepwater Horizon found floating in May 2010, as well as oil collected by BP in October 2012, during an inspection of the 80-ton cofferdam that had been abandoned at the seafloor after its use in a failed attempt to cover the Macondo well in 2010.

The team's gas chromatography analysis of BP's cofferdam samples definitively showed that it was not the sole source of the leak as there were no olefins present.

Prior to the analysis the cofferdam had become the prime suspect as the source when BP found small amounts of oil leaking from its top.

BP scientists acquired oil samples from this leak point before sealing the leak, thinking they had resolved the problem. However, the sheens on the sea surface persisted, and the lack of olefins pointed to another source entirely.

When Valentine and Reddy compared the chemical makeup of the sheens with debris found floating in 2010, they found a match. That debris, which came from the rig itself, was coated with oil and was contaminated by drilling mud olefins.

"The ability to fingerprint synthetic hydrocarbons allowed us to crack this case," Valentine said. "We were able to exclude a number of suspects and match the olefin fingerprint in the new oil slicks to that of the wreckage from the sunken rig."

The chemical analysis also told researchers which sheens had surfaced more recently than others, allowing them to reconstruct a trajectory for local ocean currents that pointed back to the oil's source.

By looking for sheens that showed the least amount of evaporation, they determined that oil surfaced closer to Deepwater Horizon wreckage than to the cofferdam site.

To explain how the oil might be trapped and released from the wreckage, the scientists point out that when the Deepwater Horizon rig sank, it was holding tanks containing hundreds of barrels of a mixture of drilling mud and oil.

Over time, corrosive seawater can create small holes through which oil can slowly escape to the surface. The researchers suspect that the containers on the rig holding trapped oil may be the source of the recent oil sheen.

In addition to Valentine and Reddy, the research team consisted of Christoph Aeppli and Robert Nelson of WHOI, and Matthias Kellermann of UCSB.

The Gulf of Mexico Research Initiative, Woods Hole Oceanographic Institution and a Swiss National Science Foundation Postdoctoral Fellowship also funded the research.

-NSF-