Light availability and temperature, not increased CO2, will structure future meadows of Posidonia oceanica

• Published in: Aquatic Botany
• Main Authors: Hendriks, Iris E., Olsen, Ylva S., Duarte, Carlos M.
• Other Authors: Biological and Environmental Sciences and Engineering (BESE) Division, Marine Science Program, Red Sea Research Center (RSRC), Global Change Department, IMEDEA (CSIC-UIB), Instituto Mediterráneo de Estudios Avanzados, C/Miquel Marqués 21, 07190 Esporles, Mallorca, Spain, The UWA Oceans Institute and School of Biological Sciences, The University of Western Australia, 35 Stirling Highway, Crawley 6009, Australia
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier BV 2017
• Subjects: Seagrass; Global warming; Temperature; Ocean acidification; Light limitation
• Online Access: http://hdl.handle.net/10754/622922; https://doi.org/10.1016/j.aquabot.2017.02.004

We evaluated the photosynthetic performance of Posidonia oceanica during short-term laboratory exposures to ambient and elevated temperatures (24–25°C and 29–30°C) warming and pCO2 (380, 750 and 1000ppm pCO2) under normal and low light conditions (200 and 40μmol photons m−2s−1 respectively). Plant growth was measured at the low light regime and showed a negative response to warming. Light was a critical factor for photosynthetic performance, although we found no evidence of compensation of photosynthetic quantum efficiency in high light. Relative Electron Rate Transport (rETRmax) was higher in plants incubated in high light, but not affected by pCO2 or temperature. The saturation irradiance (Ik) was negatively affected by temperature. We conclude that elevated CO2 does not enhance photosynthetic activity and growth, in the short term for P. oceanica, while temperature has a direct negative effect on growth. Low light availability also negatively affected photosynthetic performance during the short experimental period examined here. Therefore increasing concentrations of CO2 may not compensate for predicted future conditions of warmer water and higher turbidity for seagrass meadows. This research was supported by the MedSeA project (www.medsea-project.eu, contract number 265103 of the Framework Program 7 of the European Union), and ESTRESX (ref. CTM2012-32603), funded by the Spanish Ministry of Economy and Competitiveness. I.E.H. was supported by a JAE-DOC fellowship (CSIC, Spain). YSO was funded by a Marie Curie IEF from the European Union Seventh Framework Programme (FP7/2007–2013) under grant agreement no. 254297: FP7-PEOPLE-2009-IEF.