51
original way; unlike in the surrounding abyssal environment, their productivity is
very high (incomparable biomass) and their specific diversity (with the exclusion of
microbes) is low (a few hundred species identified to date). However, their faunal
communities are original; 99 % of species are endemic, and some of them are “living
fossils” having survived major extinction events. The biotope, high in compounds
reputed to be toxic, is extreme, compared to all environments known so far. Microorganisms which proliferate in these environments also show very specific characteristics, growth at very high temperatures and original and heat-stable compounds.
Sulphide extraction would have destructive effects on hydrothermal ecosystems
on a local scale. However, this environment is naturally very unstable due to volcanic activity, and the restoration of a hydrothermal system destroyed by sulphide exploitation can be expected to be relatively fast, taking a few years. The direct effects
of large-scale exploitation would of course be more damaging and the resilience or
restoration of biological communities longer and more random.
Communities of species fixed to sulphide deposits are far less well known that
those of hydrothermal vents, on which the majority of scientific investigation efforts are focused. These communities would of course be destroyed during extraction, and those fixed to surrounding volcanic rocks as well as those colonising the
sediment accumulated in dips could suffer the secondary effects of the redistribution of particle plumes on the seabed.
It was recently shown that hydrogen could be naturally produced in hydrothermal
systems through the reaction of water with ferromagnesian minerals in rocks. These
phenomena occur either at low temperatures at “inactive” serpentinized seamounts
or at high temperatures at “active” hydrothermal chimneys. The inventory of sites
producing large quantities of natural hydrogen is far from complete, however many
of them have already been identified at depths of over 4,000 m.
The extraction of natural hydrogen could be expected to mainly have consequences on the hydrothermal ecosystem, chemically altering the environment on a
local scale. These processes could result in the local extinction of biological communities associated with these environments. Furthermore, disturbance by hydrothermal plumes could also affect the dispersal of the larvae of organisms living in
these systems, restricting gene flows between sites on a regional scale.
Cobalt- and Platinum-rich Crusts
The first systematic investigations of these resources began in 1981 in the Central
Pacific Ocean. These crusts develop on indurated substrates, in conditions of strong
currents and low sedimentation rates. They are often found on structures situated
above the ocean floor, seamounts, at depths ranging from 400 to 4,000 m.
Recent efforts to study these environments have shown that these are “islets”
rich in biomass and in biological diversity, for animal communities living both on
the seabed and in the water column. However, these environments are still difficult
for the scientific community to access and the inventory of their biodiversity remains quite incomplete, especially for small organisms. Benthic fauna is believed to
2 Deep-sea Environment
original way; unlike in the surrounding abyssal environment, their productivity is
very high (incomparable biomass) and their specific diversity (with the exclusion of
microbes) is low (a few hundred species identified to date). However, their faunal
communities are original; 99 % of species are endemic, and some of them are “living
fossils” having survived major extinction events. The biotope, high in compounds
reputed to be toxic, is extreme, compared to all environments known so far. Microorganisms which proliferate in these environments also show very specific characteristics, growth at very high temperatures and original and heat-stable compounds.
Sulphide extraction would have destructive effects on hydrothermal ecosystems
on a local scale. However, this environment is naturally very unstable due to volcanic activity, and the restoration of a hydrothermal system destroyed by sulphide exploitation can be expected to be relatively fast, taking a few years. The direct effects
of large-scale exploitation would of course be more damaging and the resilience or
restoration of biological communities longer and more random.
Communities of species fixed to sulphide deposits are far less well known that
those of hydrothermal vents, on which the majority of scientific investigation efforts are focused. These communities would of course be destroyed during extraction, and those fixed to surrounding volcanic rocks as well as those colonising the
sediment accumulated in dips could suffer the secondary effects of the redistribution of particle plumes on the seabed.
It was recently shown that hydrogen could be naturally produced in hydrothermal
systems through the reaction of water with ferromagnesian minerals in rocks. These
phenomena occur either at low temperatures at “inactive” serpentinized seamounts
or at high temperatures at “active” hydrothermal chimneys. The inventory of sites
producing large quantities of natural hydrogen is far from complete, however many
of them have already been identified at depths of over 4,000 m.
The extraction of natural hydrogen could be expected to mainly have consequences on the hydrothermal ecosystem, chemically altering the environment on a
local scale. These processes could result in the local extinction of biological communities associated with these environments. Furthermore, disturbance by hydrothermal plumes could also affect the dispersal of the larvae of organisms living in
these systems, restricting gene flows between sites on a regional scale.
Cobalt- and Platinum-rich Crusts
The first systematic investigations of these resources began in 1981 in the Central
Pacific Ocean. These crusts develop on indurated substrates, in conditions of strong
currents and low sedimentation rates. They are often found on structures situated
above the ocean floor, seamounts, at depths ranging from 400 to 4,000 m.
Recent efforts to study these environments have shown that these are “islets”
rich in biomass and in biological diversity, for animal communities living both on
the seabed and in the water column. However, these environments are still difficult
for the scientific community to access and the inventory of their biodiversity remains quite incomplete, especially for small organisms. Benthic fauna is believed to
2 Deep-sea Environment