What are the ecological characteristics of.....?

Question

Hydrothermal vents -vs- cold seeps

Answer 1

Unlike hydrothermal vents, which are volatile and ephemeral environments, cold seeps emit at a slow and dependable rate. Likely owing to the differing temperatures and stability, cold seep organisms are much longer-lived than those inhabiting hydrothermal vents. Indeed, recent research has revealed seep tubeworms to be the longest living noncolonial invertebrates known, with a minimum lifespan of between 170 and 250 years.




Physical properties
Hydrothermal vents in the deep ocean typically form along the Mid-ocean ridges, such as the Mid-Atlantic Ridge. These are locations of upwellings of ascending mantle plumes occur between two tectonic plates at a divergent boundary.[2]

The water that issues from hydrothermal vents consists mostly of ground water that has percolated down into hot regions from the surface, but it also commonly contains some portion of primordial water that originated deep underground and is only now surfacing for the first time. The proportion varies from location to location.

The water emerges from a hydrothermal vent at temperatures ranging up to 400°C, compared to a typical 2°C for the surrounding deep water. The high pressure at these depths significantly expands the thermal range at which water remains liquid, and so the water doesn't boil. Water at a depth of 3,000 m and a temperature of 407°C becomes supercritical.[3] However the increase in salinity pushes the water closer to its critical point.

Some hydrothermal vents form roughly cylindrical chimney structures. These form from minerals that are dissolved in the vent fluid. When the super-heated water contacts the near-freezing sea water, the minerals precipitate out to form particles which add to the height of the stacks. Some of these chimney structures can reach heights of 60 m.[4] An example of such a towering vent is "Godzilla", a structure in the Pacific Ocean near Oregon that rose to 40 m before it fell over.

The initial stages of a vent chimney begin with the deposition of the mineral anhydrite. Sulfides of copper, iron and zinc then precipitate in the chimney gaps, making it less porous over the course of time. Vent growths on the order of 30 cm per day have been recorded.[5]

Chimney structures that emit a cloud of black material are called "black smokers", named for the dark hue of the particles they emit. The black smokers typically emit particles with high levels of metal sulfides. Vents that emit lighter-hued minerals have also been discovered, and these are named "white smokers". They are typically lower in temperature than black smokers, and are deficient in copper, iron and hydrogen sulfide, while being rich in zinc.[5]

A cold seep (sometimes called a cold vent) is an area of the ocean floor where hydrogen sulfide, methane and other hydrocarbon-rich fluid seepage occurs. Cold seeps are distinct from hydrothermal vents: the former's emissions are of the same temperature as the surrounding seawater, whereas the latter's emissions are super-heated. Cold seeps constitute a biome supporting several endemic species.

Entire communities of light independent organisms - known as extremophiles - develop in and around cold seeps, most relying on a symbiotic relationship with chemoautotrophic bacteria. These prokaryotes, both Archaea and Eubacteria, process sulfides and methane through chemosynthesis into chemical energy. Higher organisms, namely vesicomyid clams and siboglinid tube worms use this energy to power their own life processes, and in exchange provide both safety and a reliable source of food for the bacteria. Other bacteria form mats, blanketing sizable areas in the process.

Answer 2

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