Minerals Report - International Seabed Authority

the mussel's nutrition. When experimentally moved away from active
venting these mussels do survive, although considerable weight loss occurs.
The mussel blood lacks specific proteins for the binding and transport of
sulphide and oxygen that are found in the vestimentifera and clams 4 .
Ectosymbioses
The EPR Pompei worm Alvinella pompejana represented in Figure 3,
has specialized structures on its dorsal surface that are colonised by a diverse
community of bacteria, including large filamentous forms visible to the naked
eye. While described as the most highly evolved epibiotic association among
all marine invertebrates, the functional role of the Pompeii worm’s bacteria
remains uncertain. They may serve as a source of nutrition for the worm or in
detoxifying the microenvironment within the worm’s tube 11 . The worm does
have a functional digestive system and exhibits deposit-feeding behaviour.
Since at least some of the epibiotic bacteria are know to be chemosynthetic,
and are probably sulphide oxidizers, they could both provide a
supplementary food source for A. pompejana and act as a barrier against the
diffusion of hydrogen sulphide into the worm’s tissues.
Free-living microbial growth
Microorganisms can also grow abundantly on animal and mineral
surfaces that are exposed to hydrothermal fluids 12, 13 . Filamentous bacteria
often produce dense aggregations that are visible to the naked eye as fluffy
tufts and mats. These surface-growing bacteria are a potential food source for
grazing and deposit-feeding animals such as snails, limpets and worms.
These same microbial films can be detached from surfaces by turbulence, and
either consumed by filter or suspension feeding animals around the vent or
exported to the surrounding deep sea.
3.2 MAR Vent Ecosystems
The visually spectacular vestimentiferan tubeworms, the archetypal
organisms of vents in the eastern Pacific, are conspicuously absent from
known vent sites on the Mid-Atlantic Ridge.
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