title: Intertidal oysters reach their physiological limit in a future high-CO2world.
abstract: Sessile marine molluscs living in the intertidal zone experience periods of internal acidosis when exposed to air (emersion) during low tide. Relative to other marine organisms, molluscs have been identified as vulnerable to future ocean acidification; however, paradoxically it has also been shown that molluscs exposed to high CO2environments are more resilient compared with those molluscs naive to CO2exposure. Two competing hypotheses were tested using a novel experimental design incorporating tidal simulations to predict the future intertidal limit of oysters in a high-CO2world; either high-shore oysters will be more tolerant of elevatedPCO2because of their regular acidosis, or elevatedPCO2will cause high-shore oysters to reach their limit. Sydney rock oysters,Saccostrea glomerata, were collected from the high-intertidal and subtidal areas of the shore and exposed in an orthogonal design to either an intertidal or a subtidal treatment at ambient or elevatedPCO2, and physiological variables were measured. The combined treatment of tidal emersion and elevatedPCO2interacted synergistically to reduce the haemolymph pH (pHe) of oysters, and increase thePCO2in the haemolymph (Pe,CO2) and standard metabolic rate. Oysters in the intertidal treatment also had lower condition and growth. Oysters showed a high degree of plasticity, and little evidence was found that intertidal oysters were more resilient than subtidal oysters. It is concluded that in a high-CO2world the upper vertical limit of oyster distribution on the shore may be reduced. These results suggest that previous studies on intertidal organisms that lacked tidal simulations may have underestimated the effects of elevatedPCO2.
authors.affiliation: School of Science and Health, Western Sydney University, Penrith, NSW 2750, Australia elliot.scanes@sydney.edu.au.|School of Life and Environmental Sciences, The University of Sydney, Camperdown, NSW 2006, Australia.
authors.forename: Elliot
authors.identifier: 0000-0001-7520-3804
authors.initials: E
authors.lastname: Scanes
authors.affiliation: School of Life and Environmental Sciences, The University of Sydney, Camperdown, NSW 2006, Australia.
authors.forename: Laura M
authors.initials: LM
authors.lastname: Parker
authors.affiliation: Department of Primary Industries, Port Stephens Fisheries Research Institute, Taylors Beach Road, Taylors Beach, NSW 2316, Australia.
authors.forename: Wayne A
authors.initials: WA
authors.lastname: O'Connor
authors.affiliation: Integrative Ecophysiology, Alfred Wegener Institute Helmholtz Institute for Polar and Marine Research, Am Handelshafen 12, Bremerhaven D-27570, Germany.
authors.forename: Laura S
authors.initials: LS
authors.lastname: Stapp
authors.affiliation: School of Life and Environmental Sciences, The University of Sydney, Camperdown, NSW 2006, Australia.
authors.forename: Pauline M
authors.initials: PM
authors.lastname: Ross
mesh_terms: D000064:Acclimatization; D000818:Animals; D059001:Aquatic Organisms / Q000254:growth & development / Q000502:physiology; D001481:Basal Metabolism; D002245:Carbon Dioxide / Q000032:analysis* / Q000378:metabolism*; D006458:Hemolymph / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D010125:Ostreidae / Q000254:growth & development / Q000502:physiology*; D012623:Seawater / Q000032:analysis*
chemical_list: D002245:Carbon Dioxide
keywords: Emersion; Hypercapnia; Mollusc; Multiple stressors; Ocean acidification