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1 Study Summary
The Exuberant and Extraordinary Life Around
Hydrothermal Chimneys
Discovered in the 1970s, ecosystems related to the expulsion of hydrothermal fluids are
today known to host exuberant and extraordinary communities, in as far as their development is based not on photosynthesis, like almost all life on our planet, but on chemosynthesis. Micro-organisms are the founding elements of these systems which comprise
hundreds of species of invertebrates, often large in size and mostly new to science.
Knowledge of these environments and the life developing there is still quite incomplete. Scientific progress in the understanding of how these ecosystems work
and how organisms adapt to the strong constraints of the environment leads us to
believe that many scientific discoveries are still to come. It is therefore crucial to
preserve these unique ecosystems.
Beyond active hydrothermal sites, very few data exist on the nature and distribution of fauna associated with ocean ridges and volcanic back-arc systems. Nevertheless, the complexity of their topography, its influence on hydrodynamics as well as
the heterogeneity of hard and soft substrates are thought to enable the coexistence
of assemblages of highly diversified specific organisms, with a majority of fixed
suspension feeders on rocky substrates (with, for instance, gardens of solitary corals
or sponges) and mobile detritus feeders on and in soft sediment.
In these systems, the exploitation of sulphide deposits would have a direct impact
on the benthic ecosystem of inactive metal deposits (destruction of the environment
and living organisms) and indirect impacts related to the propagation of sediment
plumes (alteration of the environment’s physical and chemical characteristics for the
pelagic ecosystem) and their sediments, by mechanical and chemical effects on chemosynthetic ecosystems in active areas and adjacent benthic ecosystems. This impact
will depend on the exploitation technique developed. We note however the existence
of a natural impact lasting several tens of thousands of years, related to the dispersion
of dissolved metal elements and particles by natural plumes at active vents.
The potential exploitation of natural hydrogen produced by hydrothermal vents
would have consequences mainly on the chemosynthetic ecosystem. It would directly affect the energy source at the base of the ecosystem and chemically alter the
environment.
Furthermore, the elimination or restriction of the hydrothermal plume could also
affect the dispersal of the larvae of organisms living in these systems, restricting
gene flows between sites on a regional scale. Finally, the mechanical constraints of
exploitation structures on these fragile environments are unknown.
Specificities of Seamounts
Knowledge of the biological communities associated with cobalt-rich crusts is limited. Nevertheless, recent studies have shown that these communities are comparable
to those of other rocky substrates on seamounts, favourable environments sheltering
1 Study Summary
The Exuberant and Extraordinary Life Around
Hydrothermal Chimneys
Discovered in the 1970s, ecosystems related to the expulsion of hydrothermal fluids are
today known to host exuberant and extraordinary communities, in as far as their development is based not on photosynthesis, like almost all life on our planet, but on chemosynthesis. Micro-organisms are the founding elements of these systems which comprise
hundreds of species of invertebrates, often large in size and mostly new to science.
Knowledge of these environments and the life developing there is still quite incomplete. Scientific progress in the understanding of how these ecosystems work
and how organisms adapt to the strong constraints of the environment leads us to
believe that many scientific discoveries are still to come. It is therefore crucial to
preserve these unique ecosystems.
Beyond active hydrothermal sites, very few data exist on the nature and distribution of fauna associated with ocean ridges and volcanic back-arc systems. Nevertheless, the complexity of their topography, its influence on hydrodynamics as well as
the heterogeneity of hard and soft substrates are thought to enable the coexistence
of assemblages of highly diversified specific organisms, with a majority of fixed
suspension feeders on rocky substrates (with, for instance, gardens of solitary corals
or sponges) and mobile detritus feeders on and in soft sediment.
In these systems, the exploitation of sulphide deposits would have a direct impact
on the benthic ecosystem of inactive metal deposits (destruction of the environment
and living organisms) and indirect impacts related to the propagation of sediment
plumes (alteration of the environment’s physical and chemical characteristics for the
pelagic ecosystem) and their sediments, by mechanical and chemical effects on chemosynthetic ecosystems in active areas and adjacent benthic ecosystems. This impact
will depend on the exploitation technique developed. We note however the existence
of a natural impact lasting several tens of thousands of years, related to the dispersion
of dissolved metal elements and particles by natural plumes at active vents.
The potential exploitation of natural hydrogen produced by hydrothermal vents
would have consequences mainly on the chemosynthetic ecosystem. It would directly affect the energy source at the base of the ecosystem and chemically alter the
environment.
Furthermore, the elimination or restriction of the hydrothermal plume could also
affect the dispersal of the larvae of organisms living in these systems, restricting
gene flows between sites on a regional scale. Finally, the mechanical constraints of
exploitation structures on these fragile environments are unknown.
Specificities of Seamounts
Knowledge of the biological communities associated with cobalt-rich crusts is limited. Nevertheless, recent studies have shown that these communities are comparable
to those of other rocky substrates on seamounts, favourable environments sheltering