Deep sea Flashcards
Describe the formation of a hydrothermal vent.
Seawater in the basaltic rock is heated by magma, and escapes through hydrothermal vents.
The hot water leeches metals from the surrounding basalts.
The metals precipitate as sulfide and sulfate minerals around the vent, forming a chimney. (copper-iron sulfides - copper iron sulfides and calcium sulfides - iron-zinc sulfides and calcium sulfates)
These generate quite a lot of nutrients and is an important source for life.
Vents result from tectonics. The main ones are found on the mid-atlantic ridge.
How do hydrothermal vents recirculate and enrich ocean water?
Through interaction with shallow volcanic heat sources and easily dissolvable trace minerals in basaltic rocks and sea floor sediments.
Heat conducted from a shallow magma chamber causes the connective flow of seawater through fractured and faulted basalt.
Mineral precipitation causes chimneys to grow upward sometimes to heights of more than 20 metres.
Describe the dense communities of organisms that live around hydrothermal vents
The base of the food webs in these vent communities consists of chemosynthetic bacteria. - They obtain energy to manufacture food by oxidising hydrogen sulfide gas.
The bacteria thrive within the vents- They are swept out by the hot water and are caught by filter-feeding organisms.
They support diverse communities of tube-dwelling worms, giant bivalves, crabs and shrimps, fish all supported by chemoautotrophic bacteria that use hydrogen sulfide as an energy source.
What are the other food sources for deep sea life other than near vents?
Dead plankton. dead fish, squid, faeces.
All other food depends on fallout of organic matter from above.
Pelagic species (<30m) feed on marine snow and benthic species are scavengers (up to 1m).
Describe the whale fall communities.
400 species live directly or indirectly on whale remains.
Tissues of mollusks host chemosynthetic bacteria.
50-100 years to completely degrade a whale carcuss.
Stages:
i. Scavengers (hagfish, sleeper sharks, crabs) eat much of the blubber and muscle tissue, takes up to 2 years)
ii. Opportunist
(invertebrates; snails, bristle worms, shrimp) eat scraps of meat and whale oil soaked into sediment. Worms live on lipid content of whale bones, takes up to 2 years)
iii. Sulfophilic (anaerobic bacteria and mussles, worms, clams and limpets) anaerobic bacteria produce H2s, form mats and live sybiotically in tissues of shellfish and worms. Crustaceans prey on other organisms. Bacteria slowly degrade remaining whale bone lipids, takes up to 50 years.
