hydrothermal vents

Question 1

what are hydrothermal vents?

Answer 1

naturally formed structures, occur on divergent plate boundaries, where tectonic plates are moving apart. The vents expel a fluid that was heated to extreme temperatures when seeping through the Earth’s crust from the ocean

Question 2

depth

Answer 2

500-5000

Question 3

light

Answer 3

none

Question 4

pressure

Answer 4

increases with depth, with every 10 m of depth there is an additional 1 atm of pressure

Question 5

temperature

Answer 5

Water coming out of the vents can be up to 400 C

But the water does not boil because of the great pressure

Waters surrounding the vents can be as low as 3-4oC

Question 6

substrate

Answer 6

Chimneys – smokestacks that form as superheated
water is extruded

This water is very rich in minerals which precipitate
out in the much colder, oxygen-rich water to form
chimneys

Up to 55 m tall (Lost City)

Pillow lava – forms during slow extrusion of lava

Question 7

the cycle of water in vent

Answer 7

Cold water seeps through cracks in seafloor

Water is heated by molten rock and chemically modified:

Oxygen is removed

Hydrogen sulfide and dissolved metals (e.g. iron, copper and zinc) are added

Heated water then rises up through crust

In cold, oxygen-rich water metal sulfides form and precipitate out

Question 8

oxygen

Answer 8

absent from vent water but present in

surrounding water

Question 9

H2S hydrogen suflide

Answer 9

present in vent water but absent from surrounding water

Question 10

pH

Answer 10

of water coming out of vents can be as low

as 2.5 (but at ‘Lost City’ pH = 9-11)

Question 11

salinity

Answer 11

remember that hydrothermal vents are one source of the salt in the ocean

Question 12

Nutrients

Answer 12

iron from vents, others may sink from shallower waters

Question 13

black smokers

Answer 13

Hottest of the vents

Mostly iron and sulfide which combine to make
black ‘smoke’

Question 14

white smokers

Answer 14

Cooler water than black smokers

Barium, calcium & silicon

Question 15

bio adaptations

Answer 15

No light means no photosynthesis

Chemosynthesis instead!

Chemical equations of photosynthesis and
chemosynthesis are very similar but the
source of energy differs (light versus hydrogen
sulfide)

Question 16

Chemoautotrophic bacteria

Answer 16

the base of hydrothermal vent food webs

Free living in the surrounding seawater AND

Live symbiotically with many vent organisms
e.g. Riftia pachyptila, Bathymodiolus thermophilus,
Calyptogena magnifica, Tevnia jerichonana

Question 17

giant vent tubeworm

Answer 17

Giant vent tubeworm (up to 2 m long) Bright red plume
(hemoglobin!)

No mouth, anus or gut

Instead: trophosome = bag full of chemoautotrophic bacteria (mutualistic association)

Bacteria make up half of Riftia’s weight

Young worms do have a gut but they absorb bacteria across their skin

Question 18

Tube worm haemoglobin

Answer 18

Unique hemoglobin which simultaneously carries O2and H2S and delivers both to the bacteria in the trophosome

Binding H2S to hemoglobin prevents both sulfide toxicity and prevents premature sulfide oxidation

Question 19

Hydrothermal vent food web

Answer 19

Primary producers: bacteria

Primary consumers: giant vent tube worm

Secondary consumers: hydrothermal vent crab

Tertiary consumers: Vulcanoctopus

Question 20

human impacts

Answer 20

Mining of iron, gold, silver, copper, zinc, cadmium, manganese and sulfur

deep-sea mining