Effects of ocean acidification on growth, pigment contents and antioxidant potential of the subtropical Atlantic red alga Hypnea pseudomusciformis Nauer, Cassano & M.C. Oliveira (Gigartinales) in laboratory

Marine ecosystems are subject to several modifications due to anthropogenic impacts, including ocean acidification caused by the absorption of excessive CO 2 present in the atmosphere. Perspectives are for dramatic modifications in seawater pH and more than 60% of the ocean surface impacted over the next 100 years by global change. In this study, ocean acidification scenarios were simulated by CO 2 enrichment into seawater in three pH levels (8.0, 7.6 and 7.2) using a bioreactor system in laboratory conditions. Experimental evaluation was performed with Hypnea pseudomusciformis Nauer, Cassano & M.C. Oliveira due to its great importance in coastal marine ecosystems for primary production and commercial interest. Contrary to our initial hypothesis, the growth rate of H. pseudomusciformis decreased significantly with decreased pH conditions, even with increased availability of CO 2 . The maximum quantum yield and chlorophyll a content were also negatively affected by the pH reduction, while an increase in antioxidant activity was observed, indicating physiological stress. The physiological responses to decreased pH conditions reflect the importance of species-level studies and corroborate the changes caused by the ocean acidification on the macroalgal species.