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apidity with which faunal communities develop around new vents is astonishing.
Within one year of the 9°N and Coaxial eruptions tube worm communities had
appeared, requiring growth at several 10’s of centimetres per year 24,27, the highest growth
rates ever reported for multicellular animals. These observations bespeak the extent to
which vent communities have adapted to exploit this ephemeral but energy-rich habitat
through their capacities for reproduction, dispersal, colonization and growth. At
Coaxial, one third of the regional pool of vent species had become established at the new
vents within 2 years of the eruption 24.
5.2 Local habitat evolution
Active hydrothermal vents are extremely dynamic environments and studies of
how vent communities respond to local environmental change provide an appreciation
of their capacity to recover from human perturbation. Studies at 13°N on the East Pacific
Rise and on the Juan de Fuca Ridge 28,29 found that alvinellid worms adapted quickly to
sulphide chimney growth and were able to colonise new areas of chimney as they were
formed. A more extensive, 4-year study of habitat and faunal community dynamics on a
hydrothermal sulphide edifice on the Juan de Fuca Ridge showed that the composition of
entire communities can be very plastic, shifting with fluid flow regimes at time scales of
weeks to months 30. These adaptations involve both recolonisation by more tolerant
organisms where hydrothermal conditions become too severe for the previous
community, as well as the progress colonisation of cooling surfaces by species less
tolerant of severe conditions. All such observations contribute to an emerging picture of
a fauna that is well adapted to the ever-changing habitat of active sulphide edifices. This
capacity to keep up with environmental change is dependent on a ready supply of adults
and larvae to recolonise disturbed or gradually changing surfaces.
6. POTENTIAL MINING IMPACTS
6.1 Nature of mining-related perturbations
Mining activities in the coming decades are likely to be concentrated in very
limited areas where polymetallic sulphide deposits of commercial size are known to
occur. At these locations, extracting ore will result in removal of the substratum and
production of a particulate plume. Some organisms will be directly killed by mining
machinery, while others nearby risk smothering by material settling from the particulate
plume. Individuals surviving these perturbations would be subject to a radical change in
habitat conditions with hard substrata being replaced by soft particulates settling from
the mining plume. These particulates could also clog hydrothermal conduits, depriving
established vent communities of their vital fluid supply. At sedimented hydrothermal
110 International Seabed Authority