title: Physiological responses of a population of Sargassum vulgare (Phaeophyceae) to high pCO2/low pH: implications for its long-term distribution.
abstract: Ocean Acidification (OA) is likely to affect macroalgal diversity in the future with species-specific responses shaping macroalgal communities. In this framework, it is important to focus research on the photosynthetic response of habitat-forming species which have an important structural and functional role in coastal ecosystems. Most of the studies on the impacts of OA involve short-term laboratory or micro/mesocosm experiments. It is more challenging to assess the adaptive responses of macroalgal community to decreasing ocean pH over long-term periods, as they represent the basis of trophic dynamics in marine environments. This work aims to study the physiological traits of a population of Sargassum vulgare that lives naturally in the high pCO2vents system in Ischia (Italy), in order to predict the species behaviour in a possible OA future scenario. With this purpose, the photosynthetic performance of S. vulgare was studied in a wild, natural population living at low pH (6.7) as well as in a population transplanted from native (6.7) to ambient pH (8.1) for three weeks. The main results show that the photochemical activity and Rubisco expression decreased by 30% after transplanting, whereas the non-photochemical dissipation mechanisms and the photosynthetic pigment content increased by 50% and 40% respectively, in order to compensate for the decrease in photochemical efficiency at low pH. Our data indicated a stress condition for the S. vulgare population induced by pH variation, and therefore a reduced acclimation capability at different pH conditions. The decline of the PSIImaximum quantum yield (Fv/Fm) and the increase of PARP enzyme activity in transplanted thalli further supported this hypothesis. The absence of the species at ambient pH conditions close to the vent system, as well as the differences in physiological traits, suggest a local adaptation of S. vulgare at pH6.7, through optimization of photosynthetic performance.
authors.affiliation: Stazione Zoologica Anton Dohrn of Naples, Integrative Marine Ecology Department, Branch office 'Villa Dohrn', Punta S. Pietro, 80077, Ischia, Naples, Italy. Electronic address: lucia.porzio@szn.it.
authors.forename: Lucia
authors.initials: L
authors.lastname: Porzio
authors.affiliation: Stazione Zoologica Anton Dohrn of Naples, Integrative Marine Ecology Department, Branch office 'Villa Dohrn', Punta S. Pietro, 80077, Ischia, Naples, Italy.
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Buia
authors.affiliation: Stazione Zoologica Anton Dohrn of Naples, Integrative Marine Ecology Department, Branch office 'Villa Dohrn', Punta S. Pietro, 80077, Ischia, Naples, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Lorenti
authors.affiliation: Department of Biology, University of Naples Federico II, Via Cinthia, 80126 Naples, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: De Maio
authors.affiliation: Department of Biology, University of Naples Federico II, Via Cinthia, 80126 Naples, Italy; Institute for Sustainable Plant Protection, The National Research Council of Italy, via Madonna del Piano 10, 50019 Sesto Fiorentino, FI, Italy.
authors.forename: Carmen
authors.initials: C
authors.lastname: Arena
mesh_terms: D002245:Carbon Dioxide / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007558:Italy; D044647:Sargassum / Q000502:physiology*; D012623:Seawater / Q000737:chemistry*
chemical_list: D002245:Carbon Dioxide
keywords: Adaptive response; Brown algae; Ecophysiology; Ocean acidification; Poly(ADP-ribosylation); Stress response