Long-term acclimation to elevated p CO 2 alters carbon metabolism and reduces growth in the Antarctic diatom Nitzschia lecointei

• Published in: Proceedings of the Royal Society B: Biological Sciences
• Main Authors: Torstensson, Anders, Hedblom, Mikael, Mattsdotter Björk, My, Chierici, Melissa, Wulff, Angela
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 2015
• Subjects: Antarctic; The Antarctic; Antarc*; Ocean acidification; Sea ice
• Online Access: http://dx.doi.org/10.1098/rspb.2015.1513; https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2015.1513; https://royalsocietypublishing.org/doi/full-xml/10.1098/rspb.2015.1513

Increasing atmospheric CO 2 levels are driving changes in the seawater carbonate system, resulting in higher p CO 2 and reduced pH (ocean acidification). Many studies on marine organisms have focused on short-term physiological responses to increased p CO 2 , and few on slow-growing polar organisms with a relative low adaptation potential. In order to recognize the consequences of climate change in biological systems, acclimation and adaptation to new environments are crucial to address. In this study, physiological responses to long-term acclimation (194 days, approx. 60 asexual generations) of three p CO 2 levels (280, 390 and 960 µatm) were investigated in the psychrophilic sea ice diatom Nitzschia lecointei . After 147 days, a small reduction in growth was detected at 960 µatm p CO 2 . Previous short-term experiments have failed to detect altered growth in N. lecointei at high p CO 2 , which illustrates the importance of experimental duration in studies of climate change. In addition, carbon metabolism was significantly affected by the long-term treatments, resulting in higher cellular release of dissolved organic carbon (DOC). In turn, the release of labile organic carbon stimulated bacterial productivity in this system. We conclude that long-term acclimation to ocean acidification is important for N. lecointei and that carbon overconsumption and DOC exudation may increase in a high-CO 2 world.