Solar UV Irradiances Modulate Effects of Ocean Acidification on the Coccolithophorid Emiliania huxleyi

• Published in: Photochemistry and Photobiology
• Main Authors: Xu, Kai, Gao, Kunshan
• Other Authors: National Natural Science Foundation of China, Chinese Academy of Sciences, China-Japan collaboration project from MOST, Program for Changjiang Scholars and Innovative Research Team of China
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2014
• Subjects: Ocean acidification
• Online Access: http://dx.doi.org/10.1111/php.12363; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fphp.12363; https://onlinelibrary.wiley.com/doi/pdf/10.1111/php.12363

Abstract Emiliania huxleyi , the most abundant coccolithophorid in the oceans, is naturally exposed to solar UV radiation (UVR, 280–400 nm) in addition to photosynthetically active radiation (PAR). We investigated the physiological responses of E. huxleyi to the present day and elevated CO 2 (390 vs 1000 μ atm; with pH NBS 8.20 vs 7.86) under indoor constant PAR and fluctuating solar radiation with or without UVR. Enrichment of CO 2 stimulated the production rate of particulate organic carbon (POC) under constant PAR, but led to unchanged POC production under incident fluctuating solar radiation. The production rates of particulate inorganic carbon (PIC) as well as PIC/POC ratios were reduced under the elevated CO 2 , ocean acidification (OA) condition, regardless of PAR levels, and the presence of UVR. However, moderate levels of UVR increased PIC production rates and PIC/POC ratios. OA treatment interacted with UVR to influence the alga's physiological performance, leading to reduced specific growth rate in the presence of UVA (315–400 nm) and decreased quantum yield, along with enhanced nonphotochemical quenching, with addition of UVB (280–315 nm). The results clearly indicate that UV radiation needs to be invoked as a key stressor when considering the impacts of ocean acidification on E. huxleyi .