title: Effects of Ocean Acidification and Temperature Increases on the Photosynthesis of Tropical Reef Calcified Macroalgae.
abstract: Climate change is a global phenomenon that is considered an important threat to marine ecosystems. Ocean acidification and increased seawater temperatures are among the consequences of this phenomenon. The comprehension of the effects of these alterations on marine organisms, in particular on calcified macroalgae, is still modest despite its great importance. There are evidences that macroalgae inhabiting highly variable environments are relatively resilient to such changes. Thus, the aim of this study was to evaluate experimentally the effects of CO2-driven ocean acidification and temperature rises on the photosynthesis of calcified macroalgae inhabiting the intertidal region, a highly variable environment. The experiments were performed in a reef mesocosm in a tropical region on the Brazilian coast, using three species of frondose calcifying macroalgae (Halimeda cuneata, Padina gymnospora, and Tricleocarpa cylindrica) and crustose coralline algae. The acidification experiment consisted of three treatments with pH levels below those occurring in the region (-0.3, -0.6, -0.9). For the temperature experiment, three temperature levels above those occurring naturally in the region (+1, +2, +4°C) were determined. The results of the acidification experiment indicate an increase on the optimum quantum yield by T. cylindrica and a decline of this parameter by coralline algae, although both only occurred at the extreme acidification treatment (-0.9). The energy dissipation mechanisms of these algae were also altered at this extreme condition. Significant effects of the temperature experiment were limited to an enhancement of the photosynthetic performance by H. cuneata although only at a modest temperature increase (+1°C). In general, the results indicate a possible photosynthetic adaptation and/or acclimation of the studied macroalgae to the expected future ocean acidification and temperature rises, as separate factors. Such relative resilience may be a result of the highly variable environment they inhabit.
authors.affiliation: Universidade Federal Rural de Pernambuco, Departamento de Biologia, R. Dom Manoel de Medeiros, s/n, Dois Irmãos, 52171-900, Recife, PE, Brazil.
authors.forename: Fernando
authors.identifier: 0000-0002-4440-4002
authors.initials: F
authors.lastname: Scherner
authors.affiliation: Instituto Coral Vivo, Estrada da Balsa, km 4,5, Arraial d'Ajuda, 45816-000, Porto Seguro, BA, Brazil.
authors.forename: Cristiano Macedo
authors.initials: CM
authors.lastname: Pereira
authors.affiliation: Instituto Coral Vivo, Estrada da Balsa, km 4,5, Arraial d'Ajuda, 45816-000, Porto Seguro, BA, Brazil.|Universidade Federal do Rio de Janeiro, Museu Nacional, Departamento de Inverterbrados, Quinta da Boa Vista, s/n, São Cristóvão, 20940-040, Rio de Janeiro, RJ, Brazil.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Duarte
authors.affiliation: Instituto Coral Vivo, Estrada da Balsa, km 4,5, Arraial d'Ajuda, 45816-000, Porto Seguro, BA, Brazil.|Universidade Federal de Santa Catarina, Departamento de Botânica, Trindade, 88010-970, Florianópolis, SC, Brazil.
authors.forename: Paulo Antunes
authors.initials: PA
authors.lastname: Horta
authors.affiliation: Instituto Coral Vivo, Estrada da Balsa, km 4,5, Arraial d'Ajuda, 45816-000, Porto Seguro, BA, Brazil.|Universidade Federal do Rio de Janeiro, Museu Nacional, Departamento de Inverterbrados, Quinta da Boa Vista, s/n, São Cristóvão, 20940-040, Rio de Janeiro, RJ, Brazil.
authors.forename: Clovis Barreira
authors.initials: CB
authors.lastname: E Castro
authors.affiliation: Universidade Federal de Santa Catarina, Departamento de Botânica, Trindade, 88010-970, Florianópolis, SC, Brazil.
authors.forename: José Bonomi
authors.initials: JB
authors.lastname: Barufi
authors.affiliation: Universidade Federal Rural de Pernambuco, Departamento de Biologia, R. Dom Manoel de Medeiros, s/n, Dois Irmãos, 52171-900, Recife, PE, Brazil.|Universidade Federal de Pernambuco, Programa de Pós-graduação em Saúde Humana e Meio Ambiente, Rua Alto do Reservatório, s/n, 55608-680, Vitória de Santo Antão, PE, Brazil.
authors.forename: Sonia Maria Barreto
authors.initials: SM
authors.lastname: Pereira
mesh_terms: D000143:Acids / Q000737:chemistry*; D002256:Carbonic Anhydrases / Q000378:metabolism; D057894:Coral Reefs; D006863:Hydrogen-Ion Concentration; D009792:Oceans and Seas; D010788:Photosynthesis; D012624:Seaweed / Q000201:enzymology / Q000502:physiology*; D013696:Temperature; D014329:Tropical Climate
chemical_list: D000143:Acids; D002256:Carbonic Anhydrases