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1998 Projects

Current Projects

Green_Ball.gif (257 bytes)Biogeochemistry/
climate and ocean

Green_Ball.gif (257 bytes)Deep-sea
community dynamics

Green_Ball.gif (257 bytes)Sub-seabed flow on continental margins

Green_Ball.gif (257 bytes)Mid-ocean ridges and submarine volcanoes

Green_Ball.gif (257 bytes)Marine microbial ecology

Green_Ball.gif (257 bytes)New tools and

Green_Ball.gif (257 bytes)Feasibility studies

Green_Ball.gif (257 bytes)High-risk initiatives

Green_Ball.gif (257 bytes)ROV infrastructure

Green_Ball.gif (257 bytes)Mooring infrastructure

Green_Ball.gif (257 bytes)Technology

Green_Ball.gif (257 bytes)Video infrastructure

Green_Ball.gif (257 bytes)Monterey Bay Aquarium/
MBARI joint projects

Green_Ball.gif (257 bytes)1997 Projects




Project 3

Patterns and consequences of sub-seabed flow on continental margins

Principal Investigator: Jim Barry

Co-investigators: Peter Brewer, Kurt Buck, Gernot Friederich, Hans Jannasch

Collaborators: Keith Kvenvolden, Tom Lorenson, Jon Martin, Geoff Wheat

This project encompasses ongoing studies at the continental margin and expands the research to other areas. There are two components:

P3A Margin tectonics and fluid flow—Beneath the seafloor lies a complex "plumbing system" that channels fluids chemically distinct from seawater. The flow of these fluids tends to be greatest along faults that fracture the margins of continents. When earthquakes occur in these regions, fluid flow surges, then tapers off to seeping levels; thus, tectonic activity appears to be a driving force in regulating sub-seafloor flow. The several cold seeps discovered by MBARI researchers over the last six years in Monterey Bay mostly occur along the traces of major faults. The question of whether fluids there originate from aquifers on land, or from compaction of the soupy sediments that accumulate on the seafloor, remains to be resolved.

The chemical composition of the fluids reflects not only their origins, but the environment through which they traversed before discharging into seawater. The mixing of seep fluids with ocean water causes chemical reactions that produce precipitates. The carbonate slabs and chimneys MBARI geologists have recovered using the ROV Ventana are composed of one type of such precipitates. Geologists would like to know whether the chemical reactions that produce carbonates are continual, or if the processes occur in episodes of short duration in geologic terms or over millennia. As with hydrothermal vents at mid-ocean ridges, cold seeps also sustain biological communities of bacteria, clams, and other organisms, which use the reduced inorganic compounds from the leaking fluids in chemosynthesis.

Institute scientists are addressing such questions within the scope of this project. Building on past MBARI studies of cold seeps, they will compare subseafloor fluids and carbonates from three locations:

  • Monterey Bay—Researchers will continue to collect fluid samples and carbonate slabs in the bay, where cold seep fluids contain relatively high levels of sulfide. Analysis of the chemical make-up of the fluids and the carbonates will shed light on their origins and evolution, and the history of fluid venting at various sites.
  • Eel River Basin off Northern California— MBARI scientists collected fluid and carbonate samples at methane-rich seeps on a research cruise in 1997.
  • Santa Barbara Basin—Seeps rich in hydrocarbons abound in this area. In Spring 1998 institute scientists plan to map the distribution of fluid flow with side-scan sonar. On a cruise with the R/V Point Lobos in October, they will use areas of high reflectivity identified on the sonar images (which usually indicate seafloor expanses of precipitates) to locate sites for collecting rock samples and seep fluids.

P3B Cold seep biology and ecology—Studies of cold seeps in Monterey Bay and elsewhere have revealed considerable variation in their resident animal communities which seems to be associated with differences in the intensity of fluid release. Seeps on the bay seafloor appear to represent a low-flow endpoint in the spectrum of seep habitats around the world and thus are valuable in comparisons with those at other sites. In 1998 institute ecologists will concentrate their investigations on seeps in the axis of the canyon, using the ROV Tiburon to venture into deeper waters, where they expect to find varieties of clams not yet studied. They will also participate in the October expedition to the Santa Barbara Basin. In laboratory studies of clams collected in a range of locations, the biologists will determine variations in clam blood physiology that appear to allow different species to thrive at sites with different environmental chemistries. The Monterey Bay and Santa Barbara findings will be compared with those from studies of seeps with more intense flows in Northern California and Sagami Bay, Japan.

The researchers will also continue documenting the distribution and abundance of cold-seep organisms of all sizes, from bacteria to snails and clams, and compare them to animal communities at non-seep control sites. A new branch of this cold-seep census will focus on foraminiferans, microscopic organisms whose shells are abundant in fossils and carbonates. Sizable numbers of forams exist at cold seeps, but little is known of their role in seep ecology. Other work, with collaborators, will explore important links in the chemical cycling of sulfur, such as processes of sulfate reduction in seep sediment and sulfide uptake by free-living bacteria there.

Next: Mid-ocean ridges and submarine volcanoes

Last updated: 23 November 2005