ub-seafloor fluid flow systems in geological, biological, and hydrographic environments.

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Sub-seafloor fluid flow systems in geological, biological, and hydrographic environments. Many seafloor and all sub-seafloor ecosystems are inextricably linked to, and perhaps an inevitable consequence of, the flow of energy and material between the earth’s crust and the deepest portions of the overlying ocean. The direct linkages between life and planetary processes operating along deep-sea spreading centers, subduction zones, and transform faults, as well as mid-plate circulation, can only be understood through tightly integrated studies across a broad range of disciplines in geophysics, geology, chemistry, biology, and oceanography. (Figure from JOIDES Hydrogeology PPG Report (2001), http://poseidon.palaeoz.geomar.de/panels/reports.html.)

Fluid-Rock Interactions and the Subseafloor Biosphere

The oceanic crust contains the largest aquifer on Earth. Thermal circulation and reactivity of seawater-derived fluids can modify the composition of oceanic plates, can lead to the formation of hydrothermal vents that support unique micro- and macro-biological communities, and can concentrate methane to form massive methane gas and methane hydrate reservoirs. The role that transient events (e.g., earthquakes, volcanic eruptions, and slope failures) play in these fluid-rock interactions and in the dynamics of subseafloor microbial communities remains largely unknown.

The long-term sensor deployments on the ocean floor, fully networked and controllable in response to short-term changes and objectives, will provide unique observing opportunities of tectonic events and their catalytic role in biological activity. Sensors deployed on nearby moored platforms or in profiling mode in the water column, unconstrained by power limitations, will track related changes into the overlying hydrosphere. The OOI's on-demand abilities to interconnect sensor systems to make measurements, and combine data systems to analyze measurements, will empower new collaborations between the geological and marine biology communities.

Examples of Key Scientific Questions

  • What is the extent, abundance, distribution, and diversity of the sub-seafloor biosphere?
  • How do submarine hydrothermal systems and their associated biological communities vary over time?
  • What processes control the formation and destabilization of gas hydrates?
  • What role do gas hydrates play in catastrophic slope failure?