Combined effects of ocean acidification and solar UV radiation on photosynthesis, growth, pigmentation and calcification of the coralline alga Corallina sessilis (Rhodophyta)

• Published in: Global Change Biology
• Main Authors: Gao, Kunshan, 高坤山, Zheng, Yangqiao（Chinese Acad Fisheries Sci, E China Sea Fisheries Res Inst, Minist Agr, Key Lab Marine & Estuarine Fisheries Resources &, Shanghai 200090, Peoples R China）
• Format: Article in Journal/Newspaper
• Language: English
• Published: WILEY-BLACKWELL PUBLISHING, INC 2010
• Subjects: calcification; CO2; Corallina sessilis; coralline algae; ocean acidification; photosynthesis; UV; UV-absorbing compounds; Ocean acidification
• Online Access: https://doi.org/10.1111/j.1365-2486.2009.02113.x; http://dspace.xmu.edu.cn/handle/2288/1751

Previous studies have shown that increasing atmospheric CO2 concentrations affect calcification in some planktonic and macroalgal calcifiers due to the changed carbonate chemistry of seawater. However, little is known regarding how calcifying algae respond to solar UV radiation (UVR, UVA+UVB, 280-400 nm). UVR may act synergistically, antagonistically or independently with ocean acidification (high CO2/low pH of seawater) to affect their calcification processes. We cultured the articulated coralline alga Corallina sessilis Yendo at 380 ppmv (low) and 1000 ppmv (high) CO2 levels while exposing the alga to solar radiation treatments with or without UVR. The presence of UVR inhibited the growth, photosynthetic O-2 evolution and calcification rates by13%, 6% and 3% in the low and by 47%, 20% and 8% in the high CO2 concentrations, respectively, reflecting a synergistic effect of CO2 enrichment with UVR. UVR induced significant decline of pH in the CO2-enriched cultures. The contents of key photosynthetic pigments, chlorophyll a and phycobiliproteins decreased, while UV-absorptivity increased under the high pCO(2)/low pH condition. Nevertheless, UV-induced inhibition of photosynthesis increased when the ratio of particulate inorganic carbon/particulate organic carbon decreased under the influence of CO2-acidified seawater, suggesting that the calcified layer played a UV-protective role. Both UVA and UVB negatively impacted photosynthesis and calcification, but the inhibition caused by UVB was about 2.5-2.6 times that caused by UVA. The results imply that coralline algae suffer from more damage caused by UVB as they calcify less and less with progressing ocean acidification. National Basic Research Program of China [2009CB421207]; National Natural Science Foundation of China [40930846, 40676063]