Diatoms
can be dominant in conditions with a lack or excess of nitrogen
relative to phosphorus, but the Si:P ratio should also be either below
or above the theoretical value (Fig. 5b), i.e. diatoms dominate over a
certain range of Si:N ratios (Fig. 5d), within the range of 1.8–2.8, and
2.3 on average, slightly above the theoretical Redfield value.