Nutrient-saturated cultures of Skeletonema costatum were grown at 15°C and 42 combinations of photon flux density (PFD) and daylength. The growth rate increased with the daylength and PFD up to 460–630 μE m −2 s −1 (maximum 2.5 doublings day At 2000 μE m −2 s −1 the growth rate was reduced by 45%. The chlorophyll (chl) content of the cells and the rate of production of carbon per unit chlorophyll and ambient light increased for declining light regimes as did cellular nitrogen and carbon. The N/C ratio, cellular phosphorus and ratios between in vivo fluorescence, with and without DCMU, and chlorophyll varied negligibly. The ATP/C ratio was linearly related to the growth rate. The results were described mathematically. The chl/C ratio was low both in strong light and in marginally low light, corresponding to low cellular chlorophyll and high cellular carbon, respectively. The observed increase in cellular nitrogen and carbon at shade adaptation probably represent an increase in the size of internal stores of organic nitrogen and may imply that Skeletonema cells become enriched with organic nitrogen when staying in nitrate-rich subsurface layers, e.g. in or below a nutricline. However, close to zero growth in marginal light the cells become greatly enriched with respect to every measured factor. Such cells may be physiologically resting stages which may ensure survival during dark periods and promote rapid development during the initial phase of blooms. Cultures and natural blooms of Skeleronema in the Trondheimsfjord exhibit very similar patterns of variation.
No takes yet. Share an insight, caveat, or question.
Sakshaug et al. (1986) studied this question.