Leg 4: Deep-sea Chemistry
The primary mission for this expedition is to investigate the chemistry of the pore water—water that occupies the space between seafloor sediment particles—that surrounds various geologic features and active natural gas vents in the Gulf of California.
Peter Brewer's research group will use as their primary tool a laser Raman spectrometer, which can bounce a specially-tuned laser beam off of almost any object or substance, and receive back a signal that provides information about that object's chemical composition and molecular structure. This tool will allow the group to get chemical data back from the seafloor in real time.
In addition, the research team plans to take a series of push cores for pore-water sampling for comparison with the Raman and long-term studies. Gas and water samples will also be collected near the vents to study their impact on the local water chemistry, and for comparison with local gas hydrate compositions.
If natural oil seeps are found, the group plans to study oil droplets, measuring how quickly they rise to the surface. They will also measure the release of natural gas from the droplets as they transit up to the surface. This provides in microcosm a natural analogy of processes occurring at human-induced oil releases.
In addition, water samples will be collected using CTD casts for collaborators J. Martín Hernández Ayón and Gabriela Y. Cervantes from the Universidad Autónoma de Baja California in Ensenada, and for Joseph Murray and Abbey Chrystal—graduate students from University of California, Santa Cruz.
Dr. Hernández Ayón is studying the inorganic carbon system, ocean acidification, and biogeochemistry in coastal regions near Baja California and the Sea of Cortez with a special interest in the oxygen minimum zone. Joseph Murray is interested in the effects of coastal runoff and its impact on nitrogen-based nutrients. Abbey Chrystal is a paleo-oceanographer looking at the record of long-term changes in seawater pH recorded in the sediments.