Hydrothermal vents in the deep sea bed support anomalously large biomasses, and are a relatively recent discovery - the first vent was found in 1977 by ALVIN. They are associated with depths of 2000-3000m and issue water rich in bacterial floc at up to 350C. At the prevailing pressure, the water does not boil until 450C.
They form along the Mid-Atlantic ridge, amonst other expansion and subduction zones, as water is cycled down through cracks in the benthos, is heated by a magma chamber or dike, and cycled back up at a reduced density owing to the temperature increase. The water, now filled with elements and minerals as it has filtered through the rock, re-emerged in a mega-plume with steady venting.A smoker may be black or white depending on its chemistry.
Hydrothermal Vent Life
There IS light down at the vents, in the form of crystalloluminescence - seawater quenches the 350C brine, and so dissolved minerals re-crystallise, causing a luminescence effect. In chemiluminescence, energy is released by chemical reactions in the vent water, enough to emit light, but not to produce significant quantities of heat. During triboluminescence, mineral crystals crack from the cold or bang together in the turbulent erupting plume, and a flash of light is produced from the friction, impact or breakage. Somoluminescence is the luminescence that is excited in a substance by the passage of sound waves through it - in the deep, this is primarily what happens when microscopic bubbles in the hot fluid collapse. This light energy is not enough for any living organism to be able to depend upon. Instead, sulphur is utilised in chemosynthesis. The Anglerfish uses bio-luminescence to attract and confuse its prey!
The metabolic rate of abyssal bacteria is 100x slower than that of bacteria at atmospheric pressure, same temperature but maintained in the dark. This was discovered when the water-filled, sunken ALVIN was recovered after one year of submergence, and an exposed lunch was found to still be in perfect condition!
A hydrothermal vent is colonised by the vestimentiferans - huge worms, which in this case are Tubeworms. Jericho worms, Avinella pompejana (Pompeii worm) and small crustaceans then appear, before the appearance of the Riftia pachyptila worm species, amongst further crustaceans and Zoarchid fish.
The Pompeii Worm (Alvinella pompejana) lives in the highest temperature known for any higher organism: their head stays in the seawater at 22C, but their butt is rooted in the vent water at 80C. It also has a carpet of bacteria on its back. Riftia pachyptila ingest a significant quantity of bacteria in to its trophosome, a special tissue that forms half of its body mass.
The fauna is dominated by animals with chemoautrophic bacterial symbionts that oxidise the various reduced compounds issued from the fumaroles - sulphides, sulphur and thiosulphates.
Giant white clams were the first vent animals discovered, and they live on nutrients produced by symbiotic bacteria in their gills; they wedge their muscular foot in to cracks where vent fluid wells up. The Deep-sea mussel is knwon as Bathymodiolus thermophilus.
Galatheid Crabs/Bythograea thermydron alongside the spider crab also colonise hydrothermal vents.
Hydrothermal Vent shrip - Rimicaris exoculata will feed on copepods and amphipods (opportunistic animals), but their main nutrition is from the bacteria they farm on large gills. It scrapes off this bacteria with modified clays, and has a dorsal organ which may be a far red eye.
Zoarcidae fish including Thermarces cerberus feed on amphipods such as Ventiella sulfuris, as well as limpets, brachyruan crabs and copepods.
Feeding
The larger macrofauna are broken up in to a few feeding types; deposit (ooze) feeders, suspension feeders and carnivores-scavengers. However, species cannot be definitively assigned to any of these, since some deep-sea bryozoans and ascidians are deposit feeders, whilst their shallow-water relatives are suspension feeders. Bivalves and ascidian tunicates may be macrophagous predators.
The mobile and wide-ranging scavengers and carnivores are far less abundant than the detritus-feeding types, but when carrion appears, ophiuroids, crustaceans and fish accumulate around it very quickly. The first to the scene is usually the Hagfish, of the family Myxini.
Croppers are organisms that roam over the deep-sea bed cropping any food organisms they can find. Mobile deposit feeders may act as croppers, and ingest smaller deposit feeders. Gigantism is widespread amongst the opportunistic scavengers and predators. Croppers maintain the benthic prey species populations below the carrying capacity of their habitat. This means the croppers prevent competition for food amongst prey, competitive exclusion and dominance by a few superior species.
Hagfish are disgusting.
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