Minerals Report - International Seabed Authority

These bacteria are a potential food source for grazing and deposit-feeding
animals.
4. Gene Flow Along the Global Ridge System
From the time of the first discovery of hydrothermal vent communities
biologists have been asking how vent animals manage to persist in this
ephemeral and spatially discontinuous habitat. How are new vents
colonized? Why do we find the same species at vents hundreds and
thousands of km apart? Why do other species have very restricted
distributions? These questions lead to a fundamental point about how genetic
information is transmitted along the global ridge system. Most hydrothermal
vent species colonize new sites by producing larvae that have some
swimming ability but, as for most marine larvae, are primarily transported by
ocean currents. If there are barriers to the movement of larvae between
different areas of the ridge crest, their species compositions will eventually
begin to differentiate as a result of natural mutations or local extinctions. If
gene flow is maintained through the exchange of larvae, then the populations
and assemblages of species will continue to resemble each other.
Part of the answer to questions about gene flow along ridges has come
from sampling of vents around the world and comparing species inventories
between geographic locations 19 . New techniques in molecular biology are also
being applied to this problem, both to confirm differences between
morphological species and to compare populations of the same species in
order to quantify the rate of genetic exchange along the ridge axis. While
published data are few and sampling of the global ridge system is still very
incomplete, several interesting observations and hypotheses have emerged
regarding the relationship between ridge crest processes and gene flow within
the global vent fauna. First is a finding that species distribution along present
day ridges is related to tectonic plate history. One model suggests that the
global distribution of vent species and groups of species can be explained on
the basis of a radiation away from an ancestral source on the mid-Tertiary
ridges in the eastern Pacific. The entire global ridge fauna has ancestral ties to
the eastern Pacific vent fauna, through shared species, genera and families,
and can be seen as a subset of it since the greatest number of vent species is
found on the northern EPR. When comparing the vent faunas of different
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