Exam Revision

Question 0

What is the Redfield Ratio O2:C:N:P?

Answer 0

138:106:16:1.

Question 1

Where do ions in seawater come from?

Answer 1

Major cations (Na+, K+, Ca+) from river water but major anions (Cl-, SO42-, HCO3-) from volcanic outputs.

Question 2

What are the main bio limiting nutrients?

Answer 2

N, P, Si and Fe.

Question 3

What is the thermocline?

Answer 3

An area where the temperature changes more rapidly with depth than in layers above or below.

Question 4

How is density controlled?

Answer 4

Mainly by temperature but also salinity.

Question 5

What is the pycnocline?

Answer 5

An area where the density changes more with depth than the areas above or below it.

Question 6

What is the ocean conveyor direction?

Answer 6

N. Atlantic -> S. Atlantic -> Indian -> Pacific

Question 7

What is the role of nitrate (NO3-) in the ocean conveyor?

Answer 7

It increases along the conveyor with the most in the Pacific.

Question 8

What is the role of phosphate (PO43-) in the ocean conveyor?

Answer 8

The same as nitrate.

Question 9

What is the role of O2 in the ocean conveyor?

Answer 9

It decreases along the conveyor as nutrients and primary productivity increase. What

Question 10

What does a positive deviation from the Redfield ratio mean?

Answer 10

Nitrogen gain by processes like N2 fixation.

Question 11

What does a negative deviation from the Redfield ratio mean?

Answer 11

Nitrogen loss from processed like denitrification, annamox and N20 production.

Question 12

Why is there an N-deficit in the Indian Ocean?

Answer 12

There are low O2 levels so N used as an electron acceptor.

Question 13

What is silicon needed by?

Answer 13

Diatoms, silicoflagellates, radiolarians, sponges etc.

Question 14

What role do Diatoms play in the biological c-pump?

Answer 14

They account for ~40% of primary productivity.

Question 15

Where are siliceous sediments found?

Answer 15

Under areas of high productivity e.g. Equatorial regions (esp Pacific) & Southern Ocean. Rare in Atlantic bc water young and low in dissolved silicon.

Question 16

What is the calcium carbonate saturation horizon?

Answer 16

The depth at which calcium carbonate will start to dissolve. Ksp=[Ca2+]x[CO32-]

Question 17

Why does calcium carbonate dissolution increase with depth?

Answer 17

Because of increasing pressure and decreasing pH.

Question 18

What is the lysocline?

Answer 18

The depth at which calcium carbonate dissolution increases rapidly.

Question 19

What is the carbonate compensation depth (CCD)?

Answer 19

The depth where rate of dissolution compensates rate of deposition. The greatest depth that calcium carbonate sediments are found.

Question 20

How does CO32- affect calcium carbonate?

Answer 20

The depth of the saturation horizon, lysocline and CCD depend on CO32- content of seawater.

Question 21

How do the depth of the CCDS & lysocline change?

Answer 21

They decrease in depth along the conveyor belt.

Question 22

What is the normal atmospheric equilibrium of a gas?

Answer 22

The gas concentration a water mass would attain if it were to
equilibrate with the atmosphere at its in situ temperature and salinity. If in situ concentration = NAEC then water is saturated.

Question 23

How do you calculate % saturation?

Answer 23

[A] in situ/NAEC of A x100