CO2-driven seawater acidification increases photochemical stress in a green alga

• Published in: Phycologia
• Main Authors: Liu, Yuting, Xu, Juntian, Gao, Kunshan, 高昆山
• Format: Article in Journal/Newspaper
• Language: English
• Published: INT PHYCOLOGICAL SOC 2012
• Subjects: Ulva prolifera; CO2; Photosynthetic performance; Carbon-concentrating mechanisms; Nonphotochemical quenching; Ocean acidification
• Online Access: https://doi.org/10.2216/11-65.1; http://dspace.xmu.edu.cn/handle/2288/14694

Increased CO2 and associated acidification in seawater, known as ocean acidification, decreases calcification of most marine calcifying organisms. However, there is little information available on how marine macroalgae would respond to the chemical changes caused by seawater acidification. We hypothesized that down-regulation of bicarbonate acquisition by algae under increased acidity and CO2 levels would lower the threshold above which photosynthetically active radiation (PAR) becomes excessive. Juveniles of Ulva prolifera derived from zoospores were grown at ambient (390 mu atm) and elevated (1000 mu atm) CO2 concentrations for 80 days before the hypothesis was tested. Here, the CO2-induced seawater acidification increased the quantum yield under low levels of light, but induced higher nonphotochemical quenching under high light. At the same time, the PAR level at which photosynthesis became saturated was decreased and the photosynthetic affinity for CO2 or inorganic carbon decreased in the high-CO2 grown plants. These findings indicated that ocean acidification, as an environmental stressor, can reduce the threshold above which PAR becomes excessive. National Basic Research Program of China [2009CB421207, 2011CB200902]; National Natural Science Foundation [41120164007, 40930846]; Program for Changjiang Scholars and Innovative Research Team [IRT0941]; MOST [S2012GR0290]