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Evolution can be examined by studies of on-going processes<br />
and by analysis of present patter~s in vie~ of hi~torical<br />
events. Extension of the populatIon genetIc studIes to<br />
comparisons on the species level will reveal taxonomic<br />
affinities. Smaller scales of evolution can be identified from<br />
community comparisons between separate segments of a ridge.<br />
Identification of major discontinuities in vent community<br />
composition along or among ridges should allow recognition of<br />
geographic centers of evolution. Fundamental geological<br />
differences among ridges, such as spreading rates, should be<br />
examined in terms of species diversity and adaptions in response<br />
to varying geochemical patterns. Communities in other deep-sea<br />
habitats dependent upon chemosynthetic energy are composed of<br />
different species; they may yield clues to the evolutionary<br />
origin of hydrothermal vent species. Analysis of fossil vent<br />
species in sulfides will give direct evidence of past<br />
evolutionary steps. Sedimented hydrothermal systems may<br />
preserve evidence for relationships between chemistry, bacteria,<br />
and animals.<br />
Specific data requirements include information from geology<br />
and geophysics on past ridge morphology and rifting history to<br />
identify times and methods of isolation. Parallel evolutionary<br />
adaptions to the vent habitat can be identified by comparisons<br />
of systematics and physiology. Traditional and genetic techniques<br />
should be employed in erection of animal phylogenies. A<br />
key technique to aid these studies is the refinement of<br />
mechanisms to identify the genetic differentiation in a variety<br />
of organisms.<br />
Plume Studies<br />
How do hydrothermal plumes contribute to the total biological<br />
productivity associated with vent and other benthic<br />
environments?<br />
Extensive plumes associated with hot vent systems represent<br />
the vertical and horizontal component of hydrothermally derived<br />
biologically important energy sources. These energy sources<br />
support a chemosynthesis based food chain, the significance of<br />
which is not known. The importance of plume systems as a source<br />
of chemosynthetically fixed carbon, and the fate of this organic<br />
carbon needs study. Species composition and feeding rates of<br />
zooplankton consuming plume bacteria and the role, if any,<br />
plumes have on the dispersal and nutrition of vent animal larvae<br />
are critical to understanding this system.<br />
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