Nitrogen cycle what can you say? What is the F ratio and what is it used for?

In spring in oceons the water collom is very well mixed, so the nitrate from the bottom water can come up again. Can be used by phytoplankton which are eaten by for instance copopods and so on. But with strong stratisfication nitrate can not be used in upper layers. Bakteria in the upper layer are converting parts from copopods to amonium which is used by phytoplankton. In the spring the primary production is most based on amonium. (regenerated primary production) The F ratio: how much of the primary production is based on new production. The F ration can tell us where we are in the seasonal development. Upwelling leads to nutrients coming up from the buttom – a lot of new production. In oligotrphic areas – mostlly based on regenerated production A rule of thumb is when there is a lot of regenerated nitrogen production is pretty low.