PHYSICAL CONDITIONS IN DEEP SEA ENVIRONMENTS

Question 1

Are there strict ecological zones with altitude on land? Why?

Answer 1

No - boundaries between ecological zones vary with latitude, rainfall, prevailing wind, topography etc.

Question 2

How much does pressure increase with 10m depth?

Answer 2

by ~1 atmosphere per 10m depth

Question 3

Why do deep sea organisms not require structural adaptations at depths?

Answer 3

Internal and external pressures are equalised in most organism tissues (solids and liquids are largely incompressible)

Question 4

Pressure can trap water on surfaces of unfolded proteins. What can this cause? How does the physiology of many taxa overcome this?

Answer 4

Prevents them folding into shape for correct enzyme function.
Many taxa use “chaperone” molecules (piezolytes) to remove water from unfolded proteins and promote correct folding.
Fish and decapod crustaceans use a molecule called TMAO.

Question 5

How does fish and decapod tissue TMAO conc change with depth?
What effect does this have on depth distribution of teleost fish?

Answer 5

Increase.
With increasing TMAO, teleost fish become hypertonic to seawater by <9000 metres, limiting their depth distribution.

Question 6

What is the piezothermal effect? What might this explain for vent fish and vent shrimp?

Answer 6

higher temperatures can enable tolerance of higher pressures
lower-than-expected-for-depth tissue TMAO in vent shrimp and fish

Question 7

Why does lipid composition of cell membrane vary with depth in deep-sea taxa?

Answer 7

To maintain membrane fluidity under pressure

Question 8

Calcite starts to dissolve below certain depths (CCD). How do trench amphipods overcome this?

Answer 8

Produce an aluminium hydroxide gel that coats their exoskeleton to protect its calcite mineral content from dissolving under pressure.

Question 9

Why is their some slight adiabatic warming at great depths?

Answer 9

Due to slight incompressibility of water

Question 10

What is water mass structure a consequence of? What concentration does it affect?

Answer 10

Thermohaline circulation
Deep-water oxygen concentration (& CCD)

Question 11

What is the dysphotic and aphotic zone?

Answer 11

• solar irradiance still present/detectable but insufficient for NET photosynthetic primary production
• no (detectable) solar photon flux (but some other light sources still present e.g. bioluminescence, geochemistry, physics)