The coupled effects of carbon dioxide enrichment and ultroviolet radiation on Phaeocystis globosa Scherffel

CO₂ perturbation experiments were carried out under the solar radiation with or without UV radiation (280~400 nm) in a temperature-controlled water bath to evaluate the coupled effects of CO₂ and UVR on Phaeocystis globosa Scherffel that forms harmful algal blooms. The results show that both of high CO₂ and UVR stress on the algae. The high concentration CO₂ decreases a specific growth rate and the photochemical efficiency of the algae by up to 11.0% and 10.7%, respectively, and the UVR does further them 19.2% and 41.7%. With its cell density increasing, however, their inhibition to the alga was declining, and to minus value. UVR decreases its maximal relative electron transpert rate and photosynthetic efficiency by 14.1% and 21.0%, respectively, in ambient air, and additional 8.2% and 17.6% in the CO₂-enriched. CO₂ enrichment increases chlorophyll a, chlorophyll c and carotenoids by 4.6%,5.9% and 5.2%, respectively. The UVR increases carotenoids by 4.3%. The studies indicate that the high concentration CO₂ aggravates the damage of UVR to the algae, which increaseds in carotenoids as a protective response.