ODU Chemical Oceanographer Greg Cutter Takes Leading Role in International GEOTRACES Research Program
For decades, scientists have known that they can learn a lot about the oceans from the trace elements-iron, lead and so forth-that they find within the water column and in the sediments at the bottom. But up until now a global survey of trace elements has been hard to conduct, which is a problem Old Dominion University chemical oceanographer Gregory Cutter is trying to solve.
Cutter is one of the leaders of GEOTRACES, the largest research program ever in chemical oceanography, and which over the next dozen years is expected to cost more than $200 million and involve scientists from 30 countries. The research findings are expected to have a broad impact on our understanding of global climate change and seawater contamination.
Trace elements and their isotopes, or TEIs as they are called, are nutrients and contaminants in the oceans. They also reveal information about oceanographic processes, and, when found in layers of sediment they often hold clues about ocean and climate conditions dating back hundreds of thousands of years. To the dismay of scientists, however, because insufficient data exist about the distribution and impact of TEIs in today's oceans, they have difficulty interpreting the significance of evidence they find in sediments. They also are stymied in their attempts to create computer models based upon TEI evidence that could predict what's in store for the oceans.
GEOTRACES will allow for the first time a coordinated, global assessment of ocean TEIs. It also will establish the baseline data set that scientists can use to better understand past phenomena and to measure in the near future how human activities and global warming are affecting the health of the oceans.
Cutter believes GEOTRACES can help assess global conditions that are of interest to everyone. Because TEIs, as both essential elements and toxins, "have a direct effect on phytoplankton at the base of the food web that take up carbon dioxide, their connection to the carbon cycle and global climate is pretty direct and not esoteric at all," he adds. "That's the answer that most people today can appreciate when someone asks who cares about trace elements in the ocean."
The researcher says that the more we know about biogeochemical processes, the more we can learn about chemical signatures in the surface sediments. "And that allows us to develop proxies, as we call them, with which we can look into the ancient sediments. In other words, from what we find in GEOTRACES, we can then tell if those same things were happening in ancient oceans."
In the Sept. 1 issue of Chemical & Engineering News, a publication of the American Chemical Society, an article about the launch of GEOTRACES describes Cutter's role as chair of the program's Intercalibration Committee. In June and July, he led an expedition in the Atlantic Ocean near Bermuda aboard the 280-foot research vessel Knorr to help establish what might be called the rules of the game for GEOTRACES.
These rules, as it turns out, must be strict, while also allowing for procedural and analytic innovations that might come from a disparate set of scientists working all over the globe. The overarching rule is keep it clean, as in getting, storing and analyzing clean samples. This has been a pesky problem in the past for marine research involving TEIs.
Because trace elements, as their name implies, are found in minute quantities in the oceans, only a trace of contaminants can throw off research findings. In the past, TEI research has been compromised by traces of metals that come off the large instruments that are lowered into the water to collect samples. Other contamination can originate with sample bottles, the cables used to lower and hoist instruments into the ocean, films left on the water's surface by metals leaching off research vessels, airborne pollutants and even stray particles in laboratories.
Dependable research results also will require coordination of work going on in the some 80 labs that will participate in GEOTRACES. It is the job of Cutter's Intercalibration Committee to make sure all of the program's researchers are operating as one, big, efficient machine. "To be usable, the results from GEOTRACES must come from collection, sample processing and storage, and analytical methods that agree with the community consensus of what the correct value is of TEI concentration," he explains.
"If we're going to research the chemistry of the oceans on a global basis and if you want to compare what's happening in the Indian Ocean with what's happening in the Pacific, you have to know that data are accurate and that the value one lab gets is the same as the other lab's," he adds. One large sample of water from the expedition this past summer was divided into smaller samples and sent to all participating labs so cross-checking can be done and correct values established.
Also during last summer's expedition, the researchers tested types of instruments and equipment that will be recommended for use in GEOTRACES, as well rehearsed sampling and analysis procedures. This preliminary work is required before the central research mission can be undertaken. Next year, Cutter will lead a dry-run expedition in the Pacific Ocean, and after that he expects to continue to help guide research methodology in the U.S. portion of the program.
For the expedition, there were eight different labs on the RV Knorr that could conduct parallel tests on a single sample. In one exercise, three labs tested for iron and they got different values. "They said, 'Whoa! What's going on? What reagent are you using?'" Cutter relates. "They began swapping reagents," which, in this case, were substances used in a chemical reaction to help measure the iron, "and by the end they were getting the same values. This is intercalibration."
The researchers on the Knorr also had to overcome a problem with zinc contamination from sacrificial zinc anodes on a sampling instrument, Cutter says. Their experiences, such as solutions to the equipment glitches they encountered, will be shared in a GEOTRACES user's manual.
The GEOTRACES Scientific Steering Committee is co-chaired by Robert F. Anderson, a chemical oceanographer from Columbia University, and Gideon M. Henderson, a geochemist from Oxford University in England. The overall effort has been organized under the auspices of the international Scientific Committee on Oceanic Research (SCOR).
Individual countries are funding their own portions of the GEOTRACES investigations. Cutter's work is supported by two National Science Foundation (NSF) grants, one for $529,000 for equipment and the other for the development of GEOTRACES scientific infrastructure for $1.4 million (ODU's share is $414,000). He is the sole principal investigator on the equipment grant and the lead investigator of the science grant. The funding "represents the first phase of this international program, but with the sampling facility based here, ODU will be involved in the program for its lifetime," Cutter said.
The equipment includes a specially designed aluminum and titanium sampling carousel that holds 30 12-liter plastic sampling bottles as well as a sensors for depth, salinity, temperature, particles and chlorophyll fluorescence. This sampling package is lowered through the water column using a large winch that holds 18,200 feet of Kevlar conducting cable. Additionally, there is a 20-foot "trace metal-clean" sampling van that Cutter and his research team put aboard the RV Knorr for their intercalibration expedition this summer. This van, which serves as a portable laboratory for the processing of samples, and all of the equipment will be headquartered at ODU, but be available for use on a broad range of GEOTRACES expeditions
The carousel is based upon a previous design, "but we supersized it in the grand American tradition," Cutter says with a smile. To minimize metallic contamination, the carousel is polyurethane powder-coated, and the latest design also has corrosion-resistant titanium parts, such as nuts and bolts.
Recent TEI research has been conducted with plastic equipment that doesn't have the strength and sampling capacity of an aluminum and titanium carousel. "The plastic was effective, but time-consuming and physically demanding," Cutter says. For example, one sampling procedure might hoist back into the research boat two liters of water from 1,000 feet, and one stop at an ocean station might require continuous sampling for 24 hours. "But for an operation with the global scope of GEOTRACES, we needed to assure the sampling not only was clean and took sufficient volumes of water, but also fast." The new equipment collects enough water over a broader depth range to cut time on station by half compared to traditional methods.
While many TEIs serve as measures of the productivity of organisms in the oceans, there also are trace elements such as aluminum and manganese or stable isotopes such as carbon-13 that can give unique information about the continental sources of these elements. This helps scientists better understand ocean processes and the distribution of TEIs. Radioisotopes (unstable isotopes that are decaying and are the radioactive form of an element) such as thorium-230 can be "tracers" that provide information about the fates of trace elements-for instance, how fast they adsorb onto organic and inorganic particles.
Anderson, the Columbia professor who is co-chair of GEOTRACES, told Chemical & Engineering News that by studying "a suite of elements together, we can learn a lot more about the whole ensemble than we can by studying one element alone." He added, "The community realized a few years ago that to make a big advance in understanding how these elements and isotopes operate in the ocean, we all need to work together."
Researchers involved in GEOTRACES include chemical oceanographers such as Cutter, marine geochemists, paleoceanographers, radiochemists, trace-metal chemists, and specialists in contaminants and computer modeling. Curtis Barnes, an ODU oceanography equipment specialist, is in charge of the GEOTRACES equipment based at the university.
Cutter, who has faculty appointments in the departments of Ocean, Earth and Atmospheric Sciences as well as Chemistry and Biochemistry, has published more than 50 articles in journals, including Nature and Science, and has received funding in excess of $5 million for his research. Much of his support has come from the NSF. He is a principal investigator in the NSF-funded Hall-Bonner Program for Minority Doctoral Scholars in Ocean Science.
In 2007, he was the recipient of ODU's annual Faculty Research Achievement Award "for his outstanding research over more than 20 years at Old Dominion and for his international reputation as a scholar and scientist." He has spent more than 500 days working aboard research vessels and was among an international team of scientists who participated in a 2005 trans-Arctic research expedition, gathering samples and data that will provide information about climate cycles through the ages and present-day global warming.
Richard Zimmerman, chair of the Department of Ocean, Earth and Atmospheric Sciences, says Cutter's distinguished career at ODU includes a range of achievements outside of research. "We are equally proud of his contributions to our undergraduate and graduate education programs, as well as his service to ODU and the larger community. Two of the numerous examples of his contributions in these areas include his pioneering development of our senior capstone course sequence that gives all our undergraduate majors a real research experience in their final year at ODU, and his leadership as coordinator of the Hall-Bonner Program for Minority Doctoral Scholars."