Ocean acidification at high latitudes: Potential effects on

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TitleOcean acidification at high latitudes: Potential effects on functioning of the antarctic bivalve Laternula ellipticaAbstractOcean acidification is a well recognised threat to marine ecosystems. High latitude regions are predicted to be particularly affected due to cold waters and naturally low carbonate saturation levels. This is of concern for organisms utilising calcium carbonate (CaCO3) to generate shells or skeletons. Studies of potential effects of future levels of pCO2 on high latitude calcifiers are at present limited, and there is little understanding of their potential to acclimate to these changes. We describe a laboratory experiment to compare physiological and metabolic responses of a key benthic bivalve, Laternula elliptica, at pCO2 levels of their natural environment (430 ÃŽÅ'atm, pH 7.99; based on field measurements) with those predicted for 2100 (735 ÃŽÅ'atm, pH 7.78) and glacial levels (187 ÃŽÅ'atm, pH 8.32). Adult L. elliptica basal metabolism (oxygen consumption rates) and heat shock protein HSP70 gene expression levels increased in response both to lowering and elevation of pH. Expression of chitin synthase (CHS), a key enzyme involved in synthesis of bivalve shells, was significantly up-regulated in individuals at pH 7.78, indicating L. elliptica were working harder to calcify in seawater undersaturated in aragonite (Ar = 0.71), the CaCO3 polymorph of which their shells are comprised. The different response variables were influenced by pH in differing ways, highlighting the importance of assessing a variety of factors to determine the likely impact of pH change. In combination, the results indicate a negative effect of ocean acidification on whole-organism functioning of L. elliptica over relatively short terms (weeks-months) that may be energetically difficult to maintain over longer time periods. Importantly, however, the observed changes in L. elliptica CHS gene expression provides evidence for biological control over the shell formation process, which may enable some degree of adaptation or acclimation to future ocean acidification scenarios. Copyright 2011 Cummings et al.AcknowledgementsWe thank Malcolm Reid (University of Otago), and Jeremy Bulleid and Claire Coppard for advice on and construction of the spectrophotometer, respectively, Sarah Allen for her work in establishing the containment facility, and the K082 dive team (all NIWA) for Laternula elliptica collection. Antarctica New Zealand are thanked for their excellent logistical support on the ice, and we are particularly grateful to Paul Woodgate for his efforts in ensuring the safe importation of L. elliptica to NZ. This manuscript was improved by the helpful comments of two anonymous reviewers.

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1st AuthorCummings, V.AuthorCummings, V.Hewitt, J.van Rooyen, A.Currie, K.Beard, S.Thrush, S.Norkko, J.Barr, N.Heath, P.Jane Halliday, N.Sedcole, R.Gomez, A.McGraw, C.Metcalf, V.Year2011JournalPLoS ONEVolume6Number1DOI10.1371/journal.pone.0016069Keywordscarbon dioxidechitin synthaseheat shock protein 70oxygenchitin synthasesea water, acclimatizationacidificationanimal tissuearticlebivalvecarbon dioxide tensioncontrolled studyenvironmental impactgene expressionlatitudenonhumannucleotide sequenceocean environmentoxygen consumptionpHupregulationadaptationanimalAntarcticabiosynthesisbivalvechemistryecosystemphysiologysea, BivalviaLaternula elliptica, Adaptation, PhysiologicalAnimalsAntarctic RegionsBivalviaChitin SynthaseEcosystemHydrogen-Ion ConcentrationOceans and SeasSeawater, rank5

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TypeArticleCitationCummings, V., Hewitt, J., van Rooyen, A., Currie, K., Beard, S., Thrush, S., Norkko, J., Barr, N., Heath, P., Jane Halliday, N., Sedcole, R., Gomez, A., McGraw, C. and Metcalf, V. (2011). Ocean acidification at high latitudes: Potential effects on functioning of the antarctic bivalve Laternula elliptica. PLoS ONE, 6(1) IdentifierCummings2011Relevancerank5