title: Coralline algal physiology is more adversely affected by elevated temperature than reduced pH.
abstract: In this study we analyzed the physiological responses of coralline algae to ocean acidification (OA) and global warming, by exposing algal thalli of three species with contrasting photobiology and growth-form to reduced pH and elevated temperature. The analysis aimed to discern between direct and combined effects, while elucidating the role of light and photosynthesis inhibition in this response. We demonstrate the high sensitivity of coralline algae to photodamage under elevated temperature and its severe consequences on thallus photosynthesis and calcification rates. Moderate levels of light-stress, however, were maintained under reduced pH, resulting in no impact on algal photosynthesis, although moderate adverse effects on calcification rates were still observed. Accordingly, our results support the conclusion that global warming is a stronger threat to algal performance than OA, in particular in highly illuminated habitats such as coral reefs. We provide in this study a quantitative physiological model for the estimation of the impact of thermal-stress on coralline carbonate production, useful to foresee the impact of global warming on coralline contribution to reef carbon budgets, reef cementation, coral recruitment and the maintenance of reef biodiversity. This model, however, cannot yet account for the moderate physiological impact of low pH on coralline calcification.
authors.affiliation: Unidad Académica de Sistemas Arrecifales Puerto Morelos (Reef System Academic Unit), Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México (ICML-UNAM), Apartado postal 1152, Cancún, Q. Roo 77500, Mexico.
authors.forename: Román Manuel
authors.initials: RM
authors.lastname: Vásquez-Elizondo
authors.affiliation: Unidad Académica de Sistemas Arrecifales Puerto Morelos (Reef System Academic Unit), Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México (ICML-UNAM), Apartado postal 1152, Cancún, Q. Roo 77500, Mexico.
authors.forename: Susana
authors.initials: S
authors.lastname: Enríquez
mesh_terms: D000818:Animals; D037421:Anthozoa; D002113:Calcification, Physiologic; D057894:Coral Reefs; D057232:Global Warming; D006863:Hydrogen-Ion Concentration; D000461:Rhodophyta / Q000502:physiology*; D013696:Temperature