Hydrothermal Vents

Question 1

Where do vents occur?

Answer 1

Associate with areas of tectonic activity

Mid-ocean ridges: oceanic spreading
Volcanic seamounts

690 venting sites discovered
Models predict ~900 more at spreading centers

Question 2

Hydrothermal vent formation

Answer 2

Porous upper crust is permeated by sea water

This mixes with the hot basalt and is ejected and super heater water with new chemistry

Question 3

Vent Chemistry

Answer 3

Hydrothermal fluid: a geothermally heated fluid that escapes ocean crust

HV fluid is acidic, anoxic and enriched in energy sources for chemosynthetic bacteria as well as minerals

Significant thermal and chemical gradients form around HTV as the hydrothermal fluid mixes with seawater

Question 4

Biology at vents

Answer 4

Temperature diffuses quickly, so most organisms live at ambient temperatures of ~2C

The Pompeii worm is an exception: lives close to the vent at 80C

Organisms here have adaptations to high temperature, anoxic conditions, high metal concentration

Question 5

Food Webs at HTV

Answer 5

Mutualistic symbionts: Organisms with chemosynthetic symbionts form the base of the food web

Bacterial Mats: These also form an essential part of the base of the food web

Question 6

Zonation around HTV

Answer 6

More thermotolerant are closer to the vent
More reliant on symbiotic bacteria are closer to the vent

These two factors only explain 30% of the zonation

The zonation model is the opposite of the Menge-Sutherland model

Question 7

Gene Flow Hypothesis

Answer 7

Limited dispersal capabilities: stepping-stone model, disperse one vent at a time

Long-distance dispersal capability: Island model, dispersal from a large pool to far away vents

Question 8

Larvae of vent species

Answer 8

Some look like adults, some look different, some are lecithotrophic and some are planktotrophic

Some have large dispersal ability and others do not

Developmental modes is more related to ancestral traits, nothing species about their strategies

Question 9

Outstanding questions (3)

Answer 9

What are the patterns of connectivity: sources and sink populations, how do patterns of ocean circulation affect distribution and connectivity of populations over short and long time scales

What are the patterns of biodiversity: how many species are there, what factors drive the spatial distribution and biodiversity of benthic fauna?

What ecosystem services do hydrothermal vents provide: what is the relationship between biodiversity and ecosystem function, what role do hydrothermal vents play in global bio-geo-chemical cycles, what are the current threats