Question

Given that the global average DIN vs DIP trend in subsurface ocean waters follows: DIN = (16 x DIP) - 2.9 µmol/kg

(a). [1 point] Calculate the N* value of a parcel of water at 1000 m depth with DIN = 18.0 µmol/kg and DIP = 1.20 µmol/kg.

(b). [1 point] Based on the N* value calculated above, what process, other than photosynthesis and respiration, is likely to have altered DIN in this water parcel?

Answer 1

Part a-

The value of N calculates by Redfield ratio, which is DIN/DIP or TN/TP.

Here DIN is concentration of dissolved inorganic nitrogen.

DIP is concentration of dissolved inorganic P.

TN is concentration of total nitrogen and

TP is concentration of total phosphorus.

Now the N* or N:P = DIN ÷ DIP

N* or N:P = 18.0 µmol/kg ÷ 1.20 µmol/kg

N* or N:P = 15:1

Part b- the cause of lower nitrogen content is due to the microbial consumption of the free nitrogen into chemicals. Generally, oceans have lower nitrogen content at the surface than lower regions.