41
Chapter 2
Deep-sea Environment
Joëlle Galéron
J. Galéron ()
Centre Bretagne, Environnement profond, Ifremer, BP 70, 29280 Plouzané, France
e-mail: joelle.galeron@ifremer.fr
The Deep Sea, the Planet’s Largest Biome
The deep sea, defined as the part of the ocean over 1,000 m deep, covers 60 % of
the Earth’s surface, making it the planet’s largest biome (homogeneous ecological
formation). The geological, geochemical and physical conditions of the seabed and
water column define varied habitats, sheltering specific biological communities.
The ocean floor is composed of various distinct environments, including continental
margins, abyssal plains, oceanic trenches, mid-ocean ridges and seamounts. Over
90 % of the deep seabed is covered with fine sediments composed of particles of
biogenic (i.e. produced by living organisms), terrigenous, volcanic and authigenic
(i.e. originating from the rock where it is found) origin: they are found on abyssal
plains, but also on continental slopes. The seabed is however rockier on mid-ocean
ridges and seamounts, as well as in some isolated areas of continental slopes, into
which submarine canyons with abrupt cliffs may be cut. The marine environment is
globally characterised by an absence of sunlight, high pressure, low and relatively
constant temperatures, low currents and an oxygen content generally sufficient for
animal life to develop. In the case of the total absence of dissolved oxygen, in specific situations and in small areas, only anaerobic bacteria can develop.
Energy Sources for Deep-sea Life
Despite the lack of light, the life found in the deep-sea environment relies almost
exclusively on organic matter produced by photosynthesis. This occurs mainly in
surface waters that light can reach; it enables the development of plankton and
pelagic ecosystems in the water column. The residues of these networks settle on
the ocean floor mainly in the form of a shower of small particles, supplying animal
Y. Fouquet, D. Lacroix (eds.), Deep Marine Mineral Resources,
DOI 10.1007/978-94-017-8563-1_2, © Éditions Quæ 2014
Chapter 2
Deep-sea Environment
Joëlle Galéron
J. Galéron ()
Centre Bretagne, Environnement profond, Ifremer, BP 70, 29280 Plouzané, France
e-mail: joelle.galeron@ifremer.fr
The Deep Sea, the Planet’s Largest Biome
The deep sea, defined as the part of the ocean over 1,000 m deep, covers 60 % of
the Earth’s surface, making it the planet’s largest biome (homogeneous ecological
formation). The geological, geochemical and physical conditions of the seabed and
water column define varied habitats, sheltering specific biological communities.
The ocean floor is composed of various distinct environments, including continental
margins, abyssal plains, oceanic trenches, mid-ocean ridges and seamounts. Over
90 % of the deep seabed is covered with fine sediments composed of particles of
biogenic (i.e. produced by living organisms), terrigenous, volcanic and authigenic
(i.e. originating from the rock where it is found) origin: they are found on abyssal
plains, but also on continental slopes. The seabed is however rockier on mid-ocean
ridges and seamounts, as well as in some isolated areas of continental slopes, into
which submarine canyons with abrupt cliffs may be cut. The marine environment is
globally characterised by an absence of sunlight, high pressure, low and relatively
constant temperatures, low currents and an oxygen content generally sufficient for
animal life to develop. In the case of the total absence of dissolved oxygen, in specific situations and in small areas, only anaerobic bacteria can develop.
Energy Sources for Deep-sea Life
Despite the lack of light, the life found in the deep-sea environment relies almost
exclusively on organic matter produced by photosynthesis. This occurs mainly in
surface waters that light can reach; it enables the development of plankton and
pelagic ecosystems in the water column. The residues of these networks settle on
the ocean floor mainly in the form of a shower of small particles, supplying animal
Y. Fouquet, D. Lacroix (eds.), Deep Marine Mineral Resources,
DOI 10.1007/978-94-017-8563-1_2, © Éditions Quæ 2014