Exam Revision Flashcards
What is the Redfield Ratio O2:C:N:P?
138:106:16:1.
Where do ions in seawater come from?
Major cations (Na+, K+, Ca+) from river water but major anions (Cl-, SO42-, HCO3-) from volcanic outputs.
What are the main bio limiting nutrients?
N, P, Si and Fe.
What is the thermocline?
An area where the temperature changes more rapidly with depth than in layers above or below.
How is density controlled?
Mainly by temperature but also salinity.
What is the pycnocline?
An area where the density changes more with depth than the areas above or below it.
What is the ocean conveyor direction?
N. Atlantic -> S. Atlantic -> Indian -> Pacific
What is the role of nitrate (NO3-) in the ocean conveyor?
It increases along the conveyor with the most in the Pacific.
What is the role of phosphate (PO43-) in the ocean conveyor?
The same as nitrate.
What is the role of O2 in the ocean conveyor?
It decreases along the conveyor as nutrients and primary productivity increase. What
What does a positive deviation from the Redfield ratio mean?
Nitrogen gain by processes like N2 fixation.
What does a negative deviation from the Redfield ratio mean?
Nitrogen loss from processed like denitrification, annamox and N20 production.
Why is there an N-deficit in the Indian Ocean?
There are low O2 levels so N used as an electron acceptor.
What is silicon needed by?
Diatoms, silicoflagellates, radiolarians, sponges etc.
What role do Diatoms play in the biological c-pump?
They account for ~40% of primary productivity.
Where are siliceous sediments found?
Under areas of high productivity e.g. Equatorial regions (esp Pacific) & Southern Ocean. Rare in Atlantic bc water young and low in dissolved silicon.
What is the calcium carbonate saturation horizon?
The depth at which calcium carbonate will start to dissolve. Ksp=[Ca2+]x[CO32-]
Why does calcium carbonate dissolution increase with depth?
Because of increasing pressure and decreasing pH.
What is the lysocline?
The depth at which calcium carbonate dissolution increases rapidly.
What is the carbonate compensation depth (CCD)?
The depth where rate of dissolution compensates rate of deposition. The greatest depth that calcium carbonate sediments are found.
How does CO32- affect calcium carbonate?
The depth of the saturation horizon, lysocline and CCD depend on CO32- content of seawater.
How do the depth of the CCDS & lysocline change?
They decrease in depth along the conveyor belt.
What is the normal atmospheric equilibrium of a gas?
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.
How do you calculate % saturation?
[A] in situ/NAEC of A x100
