Photophysiology in two southern ocean phytoplankton taxa: Photosynthesis of Phaeocystis Antarctica (prymnesiophyceae) and Fragilariopsis Cylindrus (bacillariophyceae) under simulated mixed-layer irradiance

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Mills, M. M., Kropuenske, L. R., Van Dijken, G. L., Alderkamp, A. -C., Berg, G. M., Robinson, D. H., … Arrigo, K. R. (2010). Photophysiology in two southern ocean phytoplankton taxa: Photosynthesis of Phaeocystis Antarctica (prymnesiophyceae) and Fragilariopsis Cylindrus (bacillariophyceae) under simulated mixed-layer irradiance. Journal of Phycology, 46(6), 1114-1127. doi:10.1111/j.1529-8817.2010.00923.x
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TitlePhotophysiology in two southern ocean phytoplankton taxa: Photosynthesis of Phaeocystis Antarctica (prymnesiophyceae) and Fragilariopsis Cylindrus (bacillariophyceae) under simulated mixed-layer irradiance
AuthorsM. Mills, R. Kropuenske, L. Van Dijken, A. Alderkamp, M. Berg, H. Robinson, N. Welschmeyer, R. Arrigo
AbstractIn the Ross Sea, the prymnesiophyte Phaeocystis antarctica G. Karst. dominates deeply mixed water columns, while diatoms dominate shallower mixed layers. Understanding what controls the dynamics of these two phytoplankton taxa is essential because they dominate virtually all coastal polar waters, have different nutrient utilization characteristics, and support dissimilar food webs. We cultured two strains of P. antarctica and one strain of the diatom Fragilariopsis cylindrus (Grunow) Willi Krieg under three dynamic irradiance regimes that simulated different mixed-layer depths and measured their photosynthetic characteristics, cellular pigment concentrations, and cellular carbon and nitrogen content. In both species, chl a-normalized maximum carbon uptake rate (P m *) and specific growth rate were highest in the deeply mixed treatment that had a dark period. In all irradiance treatments, both (P m *) and photosynthetic efficiency (α ) were greater for the two P. antarctica strains than for the F. cylindrus strain. In contrast, P. antarctica strains were more susceptible to photoinhibition (β*) than the F. cylindrus strain. When photosynthetic rates of each phytoplankton taxon were normalized by cellular particulate organic carbon (POC), the difference in the maximal photosynthetic rate was generally reduced. In the dynamic irradiance treatment that simulated the shallowest mixed-layer irradiance, all three phytoplankton had similar ; however, the diatom had a 2-fold higher POC-normalized photosynthetic efficiency (α C). Finally, we performed calculations using the measured POC-normalized photosynthetic parameters to show that α C and can play a greater role than β C in determining the competitive outcome between P. antarctica and F. cylindrus in both shallow and deep mixed-layer environments of the Ross Sea. © 2010 Phycological Society of America.
JournalJournal of Phycology
Date2010
Volume46
Issue6
Start page1114
End page1127
ISSN00223646
SubjectsBacillariophyceae, Bacillariophyta, Fragilariopsis cylindrus, Haptophyceae, Phaeocystis antarctica
NoteCited By (since 1996):15, CODEN: JPYLA

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