Our approaches to these questions are continually evolving and include field sampling and experiments, laboratory-based experimental studies, laboratory-based analytical measurements, and computer modeling efforts. These questions also encompass different scales of study. In this context, MC&G scientists continue to undertake a blend of small, single-investigator projects, and to coordinate and participate in large multi-investigator and often multi-institutional initiatives. The ability to execute projects at these different scales is one of the factors that contribute to the on-going success of the research endeavors within MC&G and WHOI as a whole.
At the multi-institutional level, 2009 saw the launch of a major NSF-funded project led by Bernhard Peucker-Ehrenbrink that involves scientists from WHOI, the Woods Hole Research Center and the University of New Hampshire, and partnerships with East China Normal University, Shanghai, China; the Centre de Recherches Pétrographiques et Géochimiques, Nancy, France; and the University of the Fraser Valley, British Columbia, Canada. A major goal of this project is to initiate sustained observations of carbon cycling and related biogeochemical processes in six large rivers around the world—the Yangtze (Changjiang), Ganges, Brahmaputra, Congo, Lena and Fraser. Field programs were conducted on the Yangtze and Fraser rivers this past summer, with the latter expedition being spearheaded by Peucker-Ehrenbrink in conjunction with Research Associate Daniel Montluçon and MIT/WHOI Joint-Program student Britta Voss.
Other field activity this year included visits by MC&G scientists to Antarctic ice shelves, deep-sea hydrothermal systems in the Pacific and coral reefs in the Red Sea. Mak Saito and members of his research group made two visits to McMurdo Sound in Antarctica in 2009. In conjunction with his colleagues at the J.C. Venter Institute, Saito is using a combination of proteomics and genomics to examine the diversity of phytoplankton that form the base of the food chain.
Konrad Hughen undertook fieldwork in the Red Sea in a study supported by King Abdullah University of Science and Technology. Hughen’s project examines the potential vulnerability of coral reefs in the Red Sea to climate and environmental changes. He is also using the coral skeletons deposited over time to infer how the Red Sea has varied in the past. For this effort, he has successfully collected cores from corals and is examining their chemical composition, which reveals past temperature variations and other surface water changes recorded in the coral skeletons. Meg Tivey, working with Anna-Louise Reysenbach (Portland State University), carried out two sets of in situ experiments in the field to investigate microbial colonization of deep-sea hydrothermal deposits in the Pacific. The experiments, conducted at hydrothermal vents in the Lau Basin (SW Pacific) using the ROV Jason 2, and in the Gulf of California (Guaymas Basin) using the HOV Alvin, entailed razing active chimneys and placing arrays of temperature probes over the active flow in order to record the temperature history as the chimneys grew back. Molecular biological tools are being used to reveal the members of the microbial communities that developed during the re-growth of the chimneys.
Of course, collection of unique and valuable samples of the types described above in many cases represents only the starting point of an investigation. The development and application of novel analytical methods forms an essential component of many studies and is crucial for advancing our understanding of processes that drive the cycling of chemicals in the ocean.
Such analytical innovations continued to yield important advances in 2009. For example, Phoebe Lam is using synchrotron X-ray spectroscopic techniques to examine how the chemical form of iron supplied by atmospheric and marine particles becomes available to phytoplankton communities. This project, called SIRENA (Sources of Iron to the Eastern tropical North Atlantic), involves collaborations with fellow MC&G scientist Ken Buesseler, and Henrieta Dulaiova (formerly a MC&G postdoc, now at the University of Hawaii.) Its goal is to test the hypothesis that the continental margin is an important source of iron to the water column of eastern tropical North Atlantic, a region whose main iron source is generally thought to be from Saharan dust. Aerosol, sediment and suspended marine particulate samples are analyzed at synchrotron x-ray facilities such as the National Synchrotron Light Source at Brookhaven National Laboratory and the Advanced Light Source at the Lawrence Berkeley National Laboratory. Synchrotron x-ray fluorescence mapping and x-ray absorption spectroscopy is combined to determine the distribution of iron that occurs as iron oxides, iron silicates, and iron sulfides (pyrite), which are distinguishable based on their x-ray absorption spectra. Importantly, this analytical technique has revealed the presence of pyrite in water column samples, indicating that continental margin sediments must be a source of iron to the open ocean.
Ben Van Mooy has been pioneering the use of liquid chromatography coupled with mass spectrometry to explore for novel lipids, in their intact form, produced by marine microorganisms. These studies have uncovered hitherto unrecognized organic compounds, and have led to a host of exciting new discoveries. For example, Van Mooy has found that some eukaryotic phytoplankton and cyanobacteria can substitute betaine lipids and sulfur-lipids, respectively, for phosphorus-containing lipids in order to alleviate needs for the nutrient phosphorus by the cell. This finding, which represents a fundamental change in our understanding of microbial biochemistry and physiology, also has major implications for our understanding of controls of phytoplankton growth, particularly in regions of the oceans with limited available phosphorus. Van Mooy has made other exciting discoveries related to novel organic compounds in the marine environment. These include glycosphingolipids produced by marine viruses that play an important role in the infection and demise of certain types of phytoplankton such as Emiliania huxleyi. Van Mooy, working with MC&G scientist Tracy Mincer and MIT/WHOI Joint Program student Laura Hmelo, has also been exploring quorum-sensing molecules that are increasingly recognized as being crucial in cell-cell signaling by bacteria.
Two new Assistant Scientists joined the MC&G Department in 2009. Zhaohui ‘Aleck’ Wang brings expertise in the development and utilization of chemical sensors for studying the chemistry and dynamics of inorganic carbon in seawater. Aleck is particularly interested in studying inorganic carbon biogeochemistry in coastal waters. Rachel Stanley uses the abundance and isotopic compositions of dissolved gases as tracers to study carbon cycling in the upper ocean, including biological productivity and air-sea gas exchange. The innovative measurement capabilities and perspectives that Aleck and Rachel bring to WHOI very nicely complement existing expertise. We are delighted and excited to have them on board.
Overall this year, MC&G scientists have continued to make major advances in our understanding of ocean chemistry and its role in processes over a range of scales—from that involving an individual organism to global biogeochemical cycles. Advances like these continue to take place through this combination of field and laboratory studies, and through the development and application of innovative analytical techniques.
—Timothy Eglinton, Department Chair