Sensitivity of Antarctic phytoplankton species to ocean acidification: Growth, carbon acquisition, and species interaction

• Published in: Limnology and Oceanography
• Main Authors: Trimborn, Scarlett, Brenneis, Tina, Sweet, Elizabeth, Rost, Björn
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2013
• Subjects: Antarctic; Southern Ocean; Antarc*; Antarctica; Ocean acidification
• Online Access: http://dx.doi.org/10.4319/lo.2013.58.3.0997; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.4319%2Flo.2013.58.3.0997; https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.2013.58.3.0997

Despite the fact that ocean acidification is considered to be especially pronounced in the Southern Ocean, little is known about CO 2 ‐dependent physiological processes and the interactions of Antarctic phytoplankton key species. We therefore studied the effects of CO 2 partial pressure (P CO2 ) (16.2, 39.5, and 101.3 Pa) on growth and photosynthetic carbon acquisition in the bloom‐forming species Chaetoceros debilis, Pseudo‐nitzschia subcurvata, Fragilariopsis kerguelensis, and Phaeocystis antarctica. Using membrane‐inlet mass spectrometry, photosynthetic O 2 evolution and inorganic carbon (C i ) fluxes were determined as a function of CO 2 concentration. Only the growth of C. debilis was enhanced under high P CO2 . Analysis of the carbon concentrating mechanism (CCM) revealed the operation of very efficient CCMs (i.e., high C i affinities) in all species, but there were species‐specific differences in CO 2 ‐dependent regulation of individual CCM components (i.e., CO 2 and uptake kinetics, carbonic anhydrase activities). Gross CO 2 uptake rates appear to increase with the cell surface area to volume ratios. Species competition experiments with C. debilis and P. subcurvata under different P CO2 levels confirmed the CO 2 ‐stimulated growth of C. debilis observed in monospecific incubations, also in the presence of P. subcurvata . Independent of P CO2 , high initial cell abundances of P. subcurvata led to reduced growth rates of C. debilis . For a better understanding of future changes in phytoplankton communities, CO 2 ‐sensitive physiological processes need to be identified, but also species interactions must be taken into account because their interplay determines the success of a species.