50
tal margins, mainly affected by the bathymetric gradient, reflecting gradients that
evolve with depth (temperature, oxygen concentration, energy resource availability,
pressure…). Knowledge of the endemism rate of species and connectivity between
populations remains poor. They are believed to be related to various biotic and abiotic factors, the most important being distance between seamounts, hydrodynamics
and larval dispersal capacities.
Environmental Impact of Possible Exploitation of Deep-sea
Mineral Resources
Polymetallic Nodules on Abyssal Plains
Nodules represent one of the few hard substrates on abyssal plains. They are home
to a specific biological community, quite different to surrounding soft substrates, and
provide a hard substrate for large filter-feeders to fix on to. The initial consequence of
their exploitation would therefore be to destroy this specific habitat, resulting in the
local extinction of related fauna. Nodules could not be extracted without also removing the upper sediment layer on which they lie. Yet, it is in the top few centimetres of
sediment that almost all small animal communities develop, whose local species diversity is very high and yet remains almost unknown. Recent work conducted under
French licenses in the Clarion–Clipperton Zone resulted in the identification of over
10,000 invertebrates, measuring a few dozen microns, in an area of around 0.07 m
2
of sediment, among which taxonomists have been able to identify over 1,000 species
according to their morphological characteristics. For the first time, it was also shown
that the presence of nodules on the seabed influenced the structure of sediment communities, and that a sediment community disturbed by a dredging operation had not
recovered its original characteristics after a period of 26 years. The restoration of
sediment communities destroyed by mining would appear to take several decades,
or even several centuries. The redistribution of sediment in suspension in the water
column would also significantly disturb the deep-sea pelagic community and the
benthic community over far more extensive areas than those exploited.
Resources Related to Hydrothermal Systems
The first hydrothermal sulphide mineral deposits were discovered in 1978 on the
East Pacific Rise. They are found on all submarine structures of volcanic origin, at
depths between 800 and 4,100 m. Their inventory is still largely incomplete; several
hundred are thought to exist in the world’s oceans.
The specificity of environments in which sulphide deposits develop is the possibility of the presence of hydrothermal vents, with which specific communities are
associated. These ecosystems are of considerable importance. They function in an
J. Galéron
tal margins, mainly affected by the bathymetric gradient, reflecting gradients that
evolve with depth (temperature, oxygen concentration, energy resource availability,
pressure…). Knowledge of the endemism rate of species and connectivity between
populations remains poor. They are believed to be related to various biotic and abiotic factors, the most important being distance between seamounts, hydrodynamics
and larval dispersal capacities.
Environmental Impact of Possible Exploitation of Deep-sea
Mineral Resources
Polymetallic Nodules on Abyssal Plains
Nodules represent one of the few hard substrates on abyssal plains. They are home
to a specific biological community, quite different to surrounding soft substrates, and
provide a hard substrate for large filter-feeders to fix on to. The initial consequence of
their exploitation would therefore be to destroy this specific habitat, resulting in the
local extinction of related fauna. Nodules could not be extracted without also removing the upper sediment layer on which they lie. Yet, it is in the top few centimetres of
sediment that almost all small animal communities develop, whose local species diversity is very high and yet remains almost unknown. Recent work conducted under
French licenses in the Clarion–Clipperton Zone resulted in the identification of over
10,000 invertebrates, measuring a few dozen microns, in an area of around 0.07 m
2
of sediment, among which taxonomists have been able to identify over 1,000 species
according to their morphological characteristics. For the first time, it was also shown
that the presence of nodules on the seabed influenced the structure of sediment communities, and that a sediment community disturbed by a dredging operation had not
recovered its original characteristics after a period of 26 years. The restoration of
sediment communities destroyed by mining would appear to take several decades,
or even several centuries. The redistribution of sediment in suspension in the water
column would also significantly disturb the deep-sea pelagic community and the
benthic community over far more extensive areas than those exploited.
Resources Related to Hydrothermal Systems
The first hydrothermal sulphide mineral deposits were discovered in 1978 on the
East Pacific Rise. They are found on all submarine structures of volcanic origin, at
depths between 800 and 4,100 m. Their inventory is still largely incomplete; several
hundred are thought to exist in the world’s oceans.
The specificity of environments in which sulphide deposits develop is the possibility of the presence of hydrothermal vents, with which specific communities are
associated. These ecosystems are of considerable importance. They function in an
J. Galéron