Workshop Report - Ridge 2000 Program

control the genesis of many types of seafloor ore deposits that
are analogous to those found on land. Ridge crest venting of
seawater provides the ultimate energy source to support unique
chemosynthetic biological communities on mid-ocean spreading
centers. Interactions with circulating seawater strongly affect
the geometry and external dynamics of axial magma chambers,
resulting in some of the topographic and morphological variability
seen on ridge segments. The injection of vent water into
the ocean by hydrothermal activity has implications for ciculation
patterns. A detailed understanding of the individual
physical and chemical processes that constitute a hydrothermal
system will provide insight into many problems in biological,
chemical, geological. and physical oceanography. While current
research on seafloor hydrothermal circulation has begun to
address a few of these problems, new approaches and a more
focused effort will be required to achieve an interdisciplinary
view.
Four broad areas about which future hydrothermal system
research might center can be outlined. First. the physical
mechanisms of heat transfer from magma chambers or hot rock
into hydrothermal systems must be identified. Second, the
geometry of hydrothermal plumbing and the permeability structure
of the crust must be delineated. Third, information must
be gathered about the temporal variability of hydrothermal
systems. Finally, the spatial variability and tectonic associations
of hydrothermal systems must be more clearly defined.
All of these objectives involve a mixture of basic exploratory
research with more focused, detailed investigations using new
technologies and imaginative approaches.
OBJECTIVE 5: To determine the interactions of organisms with
physical and chemical environments at mid-ocean ridges.
The discovery and subsequent studies of unique biological
communities associated with hydrothermal vents along the midocean
ridge system have altered drastically many traditional
views of biological processes and adaptations on this planet.
In these hydrothermal environments, the energy source is chemical
rather than solar, with chemosynthetic bacteria rather
than photosynthetic plants at the base of the food chain.
Many of the dominant animals at the vents have incorporated
these bacteria within their tissues, resulting in unusual
symbiotic adaptations that are now proving to be far more
widespread throughout the entire Earth's biosphere than
originally imagined. Some bacteria in these environments
survive temperatures well above the range once thought
tolerable for living organisms, and continuing studies of
such microbial adaptations will be of fundamental importance
to our understanding of the basic structure of living matter.
Further definition of the extent to which chemosynthetic bacteria
affect the chemistry of vent fluids is essential to a
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