title: Reversal of ocean acidification enhances net coral reef calcification.
abstract: Approximately one-quarter of the anthropogenic carbon dioxide released into the atmosphere each year is absorbed by the global oceans, causing measurable declines in surface ocean pH, carbonate ion concentration ([CO3(2-)]), and saturation state of carbonate minerals (Ω). This process, referred to as ocean acidification, represents a major threat to marine ecosystems, in particular marine calcifiers such as oysters, crabs, and corals. Laboratory and field studies have shown that calcification rates of many organisms decrease with declining pH, [CO3(2-)], and Ω. Coral reefs are widely regarded as one of the most vulnerable marine ecosystems to ocean acidification, in part because the very architecture of the ecosystem is reliant on carbonate-secreting organisms. Acidification-induced reductions in calcification are projected to shift coral reefs from a state of net accretion to one of net dissolution this century. While retrospective studies show large-scale declines in coral, and community, calcification over recent decades, determining the contribution of ocean acidification to these changes is difficult, if not impossible, owing to the confounding effects of other environmental factors such as temperature. Here we quantify the net calcification response of a coral reef flat to alkalinity enrichment, and show that, when ocean chemistry is restored closer to pre-industrial conditions, net community calcification increases. In providing results from the first seawater chemistry manipulation experiment of a natural coral reef community, we provide evidence that net community calcification is depressed compared with values expected for pre-industrial conditions, indicating that ocean acidification may already be impairing coral reef growth.
authors.affiliation: Department of Global Ecology, Carnegie Institution for Science, Stanford, California 94305, USA.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Albright
authors.affiliation: Department of Global Ecology, Carnegie Institution for Science, Stanford, California 94305, USA.
authors.forename: Lilian
authors.initials: L
authors.lastname: Caldeira
authors.affiliation: Bodega Marine Laboratory, University of California, Davis, Bodega Bay, California 94923, USA.
authors.forename: Jessica
authors.initials: J
authors.lastname: Hosfelt
authors.affiliation: Department of Global Ecology, Carnegie Institution for Science, Stanford, California 94305, USA.
authors.forename: Lester
authors.initials: L
authors.lastname: Kwiatkowski
authors.affiliation: Department of Global Ecology, Carnegie Institution for Science, Stanford, California 94305, USA.|Stanford Nano Shared Facilities, Stanford University, Stanford, California 94305, USA.
authors.forename: Jana K
authors.initials: JK
authors.lastname: Maclaren
authors.affiliation: Department of Genetics, Stanford University School of Medicine, Stanford, California 94305, USA.
authors.forename: Benjamin M
authors.initials: BM
authors.lastname: Mason
authors.affiliation: Department of Global Ecology, Carnegie Institution for Science, Stanford, California 94305, USA.
authors.forename: Yana
authors.initials: Y
authors.lastname: Nebuchina
authors.affiliation: Bodega Marine Laboratory, University of California, Davis, Bodega Bay, California 94923, USA.
authors.forename: Aaron
authors.initials: A
authors.lastname: Ninokawa
authors.affiliation: Department of Global Ecology, Carnegie Institution for Science, Stanford, California 94305, USA.|Max Planck Institute for Meteorology, Bundesstraße 53, 20146 Hamburg, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Pongratz
authors.affiliation: Department of Global Ecology, Carnegie Institution for Science, Stanford, California 94305, USA.|Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Katharine L
authors.initials: KL
authors.lastname: Ricke
authors.affiliation: The Interuniversity Institute for Marine Sciences, The H. Steinitz Marine Biology Laboratory, The Hebrew University of Jerusalem, Eilat, Israel.|The Fredy and Nadine Herrman Institute of Earth Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, Israel.
authors.forename: Tanya
authors.initials: T
authors.lastname: Rivlin
authors.affiliation: Department of Global Ecology, Carnegie Institution for Science, Stanford, California 94305, USA.|Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Schneider
authors.affiliation: Department of Global Ecology, Carnegie Institution for Science, Stanford, California 94305, USA.
authors.forename: Marine
authors.initials: M
authors.lastname: Sesboüé
authors.affiliation: Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA.|Texas A&M University, College Station, Texas 77843, USA.
authors.forename: Kathryn
authors.initials: K
authors.lastname: Shamberger
authors.affiliation: Institute for Oceanographic and Limnological Research, Haifa, Israel.
authors.forename: Jacob
authors.initials: J
authors.lastname: Silverman
authors.affiliation: School of Medical Sciences, The University of Sydney, Sydney, New South Wales 2006, Australia.
authors.forename: Kennedy
authors.initials: K
authors.lastname: Wolfe
authors.affiliation: Department of Global Ecology, Carnegie Institution for Science, Stanford, California 94305, USA.|Department of Biology, Stanford University, Stanford, California 94305, USA.|Department of BioSciences, Rice University, Houston, Texas 77005, USA.
authors.forename: Kai
authors.initials: K
authors.lastname: Zhu
authors.affiliation: Department of Global Ecology, Carnegie Institution for Science, Stanford, California 94305, USA.
authors.forename: Ken
authors.initials: K
authors.lastname: Caldeira
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000737:chemistry / Q000378:metabolism*; D002113:Calcification, Physiologic; D002119:Calcium Carbonate / Q000378:metabolism; D057486:Carbon Cycle; D004396:Coloring Agents; D057894:Coral Reefs; D006863:Hydrogen-Ion Concentration; D009792:Oceans and Seas; D012623:Seawater / Q000737:chemistry*; D013696:Temperature
chemical_list: D004396:Coloring Agents; D002119:Calcium Carbonate