CO2 availability affects elemental composition (C:N:P) of the marine diatom Skeletonema costatum

Abstract

The effect of variable CO, concenti-ations on the elemental composition ( C N:P) of marine diatoms was investigated in 2 strains of Skeletonema costatum (Grev.) Cleve Five or 6 concentrations of dissolved molecular carbon dioxlde [CO, (aq)], ranging from 0.5 to 39 pm01 I-', were applied in dilute batch cultures. In both strains, elemental ratios were clearly dependent on [ C O . (aq)]. With decreasing CO2 concentrations, a decline in C.P and N P and an increase in C:N was observed. The close correlation between C:P or N:P and [CO, (aq)] corresponded to a ca 45 to 65?<, decrease in elemental ratios from highest (230 pm01 I-') to lowest (ca 1 pm01 I-') COz concentrations. C:N a t low [COz (aq)] was up to 24 % higher than at high [CO, (aq)]. To date, the elemental composition of marine phytoplankton has been considered to be independent of CO, availability. If dependency of the C:N:P ratio on [CO2 (aq)] proves to be a general phenomenon in marine phytoplankton, changes in the elemental composition may be expected in response to the currently observed increase in partial pressure of atmospher~c COz.