Nutrient‐ and light‐limited growth of Thalassiosira fluviatilis in continuous culture, with implications for phytoplankton growth in the ocean1

The marine diatom Thalassiosira fluviatilis was grown in a continuous culture system at 20°C on a 12:12 L:D cycle over a series of nutrient‐ and light‐limited dilution rates. Bannister’s theoretical model describing nutrient‐saturated growth gave an excellent fit to the light‐limited data. A simple extension of the model allows description of nutrient‐limited growth as well. Dark carbon loss rates were in the range 10–20% of daytime production rates at dilution rates ⩾0.25 d −1 . The relationship between Chl a :C ratios and dilution rate was linear under nutrient limitation and independent of the type of limiting nutrient. Productivity indices under nutrient limitation were found to be a hyperbolic function of dilution rate. N:C ratios were linearly correlated with dilution rate under both light and nutrient limitation, but with the regressions having opposite signs.