Interrelationships between carbon, oxygen and nitrogen metabolisms

Studies of the fluxes of carbon, nitrogen and oxygen were undertaken during
the Discovery 179 EROS cruise adjacent to and in the outflow of the Rhone.
An increase in gross planktonic production towards the mouth of the river
was observed, with rates ranging from less than 1 μmoles/litre.day offshore
to approaching 10 umoles/litre.day in the immediate area of the outflow.
There was generally a good correlation between the rates determined by
the *4C and the oxygen techniques, with apparent P.Q. values in the region
of 1.1, theoretical values calculated from nitrogen and carbon metabolisms
were similar (mean value = 1.28). These quotients imply low rates of nitrate
metabolism. Concurrent measurements of 15N-determined nitrate and
ammonia assimilation in the majority of cases gave f-ratios above 0.5, but
the C/N ratios were also high, the latter was the cause of the low P.Q.
values. The study provided an opportunity to attempt to equate new and
net production rates. Net production rates were obtained from the oxygen
flux observations, new production was calculated from the nitrogen
assimilation measurements. In the upper part of the water column there
was correspondence between the two processes, in the deeper part of the
water column the system was out of balance and there was lack of any such
agreement.