title: Internal pH regulation facilitates in situ long-term acclimation of massive corals to end-of-century carbon dioxide conditions.
abstract: The resilience of tropical corals to ocean acidification depends on their ability to regulate the pH within their calcifying fluid (pHcf). Recent work suggests pHcf homeostasis under short-term exposure to pCO2 conditions predicted for 2100, but it is still unclear if pHcf homeostasis can be maintained throughout a corals lifetime. At CO2 seeps in Papua New Guinea, massive Porites corals have grown along a natural seawater pH gradient for decades. This natural gradient, ranging from pH 8.1-7.4, provides an ideal platform to determine corals' pHcf (using boron isotopes). Porites maintained a similar pHcf (~8.24) at both a control (pH 8.1) and seep-influenced site (pH 7.9). Internal pHcf was slightly reduced (8.12) at seawater pH 7.6, and decreased to 7.94 at a site with a seawater pH of 7.4. A growth response model based on pHcf mirrors the observed distribution patterns of this species in the field. We suggest Porites has the capacity to acclimate after long-time exposure to end-of-century reduced seawater pH conditions and that strong control over pHcf represents a key mechanism to persist in future oceans. Only beyond end-of-century pCO2 conditions do they face their current physiological limit of pH homeostasis and pHcf begins to decrease.
authors.affiliation: GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Wall
authors.affiliation: GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Fietzke
authors.affiliation: Alfred-Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
authors.forename: G M
authors.initials: GM
authors.lastname: Schmidt
authors.affiliation: Max-Planck Institute for Marine Microbiology, Bremen, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Fink
authors.affiliation: Marine Botany, Bremen Center for Marine Research and Education, University of Bremen, Germany.|Max-Planck Institute for Marine Microbiology, Bremen, Germany.
authors.forename: L C
authors.initials: LC
authors.lastname: Hofmann
authors.affiliation: Max-Planck Institute for Marine Microbiology, Bremen, Germany.
authors.forename: D
authors.initials: D
authors.lastname: de Beer
authors.affiliation: Australian Institute for Marine Science, Townsville, Australia.
authors.forename: K E
authors.initials: KE
authors.lastname: Fabricius
mesh_terms: D000064:Acclimatization; D000818:Animals; D037421:Anthozoa / Q000254:growth & development / Q000502:physiology*; D002245:Carbon Dioxide / Q000032:analysis*; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D008954:Models, Biological; D010219:Papua New Guinea; D012623:Seawater / Q000737:chemistry*
chemical_list: D002245:Carbon Dioxide