Sammendrag
The objective of this study was to learn how species specific physiol ogical properties can be used to predict the optimal nutrient and lig ht regime of phytoplankton species, and thus their ability to compete under variable environmental conditions. The diatom Skeletonema co statum and the coccolithophorid Emiliania huxleyi were examined in co ntinous cultures under varying element ratios (NP25 vs. NP10) and at three different growth rates (0.22, 0.37 and 0.47 d-1). Growth irradi ance was 200 µmol m-2 s-1 provided over a 18:6 h photoperiod. The ch aracterization of the species included measurements of maximum growth rate, chemical composition, capability of gross and net phosphate up take, storage capacity of nutrients, and bio-optical properties, incl uding light absorption spectra, fluorescence exitation spectra and P ulse Amplitude Modulated fluorescence. Prelimenary results indicate that E. huxleyi has a higher potential for gross phosphorus uptake than S. costatum. Both the P:C ratio and the N:C ratio were systemati cally higher in S. costatum. The higher P:C ratio in S. costatum indi cate a lower yield of biomass per unit P. E. huxleyi had the highest light harvesting capacity per chl a, but both species had lower value s at NP10. The results and the conceptual competition model will be discussed and evaluated based on results from competition experiments with the actual species under the same exeperimental conditions as a bove.
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