N:Si ratios and the 'balance of organisms': PROWQM simulations of the northern North Sea

The simulated removal of nutrient up to the time of maximum chlorophyll was used to estimate values for diatoms and flagellates of the yield, q, of chlorophyll from nitrate or silicate. The silicate value (0.77 g chl (mol Si)− 1 in the best simulation) is novel. The yields from nitrate were 0.23-0.75 g chl (mol N)− 1, the range including both groups and all simulations. These were less than yields reported for inshore waters. Finally, the need for detailed study of the distributions of pelagic microflora and microfauna in late summer in the northern North Sea is pointed out.