Xanthophyll cycling in Phaeocystis globosa and Thalassiosira sp.: a possible mechanism for species succession

The ability of phytoplankton species to initiate photo-protective mechanism s and the rates by which they do so have been suggested to be partly respon sible for species succession. To examine whether this is also true in the c ase of diatom spring blooms preceding Phaeocystis globosa, cultures of P. g lobosa and Thalassiosira sp. were investigated under controlled laboratory conditions for differences in their xanthophyll cycling rates and abilities . It was found that P. globosa exhibited; were shifted to active and rapid xanthophyll cycling when cultures photoacclimated to 10, 50 and 100 mu mol quanta m 150 and 250 mu mol quanta m(-2) s(-1). The early spring diatom Tha lassiosira only exhibited xanthophyll cycling when acclimated to 10 mu mol quanta m(-2) s(-1). P. globosa always exhibited faster xanthophyll cycling rates than Thalassiosira, giving P. globosa a possible competitive edge ove r Thalassiosira sp. It was also found that the magnitude of xanthophyll cyc ling correlates with the intensity of light changes during the one-hour xan thophyll cycling experiments, and thus may be regarded as related to photoa cclimation. (C) 2000 Elsevier Science B.V. All rights reserved.