CO2 and dissolved inorganic carbon, and decreased concentration Throughout the brief history of ocean acidification research, a spectrum of p(CO2)

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3Guide to best practices for ocean acidiÞ cation research and data reportingPreface Ocean acidiÞ cation is an undisputed fact. The ocean presently takes up one-fourth of the carbon CO2 emitted to the atmosphere from human activities. As this CO 2 dissolves in the surface ocean, it reacts with seawater to form carbonic acid, increasing ocean acidity and shifting the partitioning of inorganic carbon species towards increased CO2 and dissolved inorganic carbon, and decreased concentration of carbonate ion. Since the beginning of the industrial revolution in the 18th century, surface-ocean acidity has gone up by 30%. The current increase in ocean acidity is a hundred times faster than any previous natural change that has occurred over the last many millions of years. In the case of unabated CO 2 emissions the level of ocean acidity will increase to three times the preindustrial level by the end of this century. Recovery from this large and rapid perturbation will require tens of thousands of years. While our understanding of the possible consequences of ocean acidiÞ cation is still rudimentary, both the scientiÞ c community and the society at large are increasingly concerned about the possible risks associated with ocean acidiÞ cation for marine organisms and ecosystems. Over the past few years, several high proÞ le reports have highlighted the urgent need to better understand the effects of changes in carbonate chemistry on marine organisms and ecosystems. Research in this Þ eld was limited to a few groups around the world until recently but the number of scientists involved in ocean acidiÞ cation research has been rapidly rising over the past few years. New coordinated national programmes are being initiated and will further augment the research efforts in this area. Students, young researchers, and established scientists inexperienced with the intricacies of the seawater carbonate chemistry will enter the Þ eld. At Þ rst sight, the experimental and intellectual challenges of conducting CO 2/pH perturbation experiments may appear trivial. pH seems easy to measure and CO 2 enrichment simple and straightforward. However, the reliable characterisation and manipulation of the carbonate system involves good analytical skills and measuring facilities and continuous monitoring of seawater chemistry in the Þ eld and during experimentation. The predictive power of Þ eld surveys and the robustness of results from perturbation experiments critically depend on proper sampling and experimental protocols, and sound statistical data analysis. The relevant expertise is available in many laboratories around the world and efforts are being made, both in the framework of national and international programmes and on a scientist by scientist basis, to pass the expertise on to those

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44interested to enter the Þ eld. We encourage funding agencies, research coordinators, and experienced scientists to further promote and facilitate the exchange of expertise relevant to ocean acidiÞ cation research. The initial learning curve in this new and rapidly growing research Þ eld is steep. Simple experiments will provide new insights and give straightforward answers. As more results come in, the picture will complicate. Some results may lead to conß icting conclusions. The reasons for this can be manifold. Different strains or species may respond differently. The sensitivity to ocean acidiÞ cation of recent isolates may differ from that of clones kept in culture over years or decades. The duration of acclimation or the rate at which the carbonate system is manipulated may also lead to different results. Species interactions may alter individual responses. Community and ecosystem changes unrelated to ocean acidiÞ cation may disguise or amplify the sensitivity to ocean acidiÞ cation. Environmental variables other than carbonate chemistry may also modify the response to ocean acidiÞ cation. However, some contradictory responses may also result from inappropriate experimental protocols, experimental artefacts, misinterpretations of the data, and inconsistent model parameterisations. To be able to distinguish these from genuine biological and biogeochemical disparity it will be crucially important for our community to apply rigorous scientiÞ c standards in our research, have access to full and detailed documentation of the analytical, experimental, statistical, and modeling approaches as well as the original data and model parameterisations. As this new and pressing Þ eld of marine research gains momentum, many in our community, including representatives of coordinated research projects, international scientiÞ c organisations, funding agencies, and scientists in this Þ eld felt the need to provide guidelines and standards for ocean acidiÞ cation research. To initiate this process, the European Project on Ocean AcidiÞ cation (EPOCA) and the Intergovernmental Oceanographic Commission (IOC) jointly invited over 40 leading scientists active in ocean acidiÞ cation research to a meeting at the Leibniz Institute of Marine Science (IFM-GEOMAR) in Kiel, Germany on 19-21 November 2008. To keep this initiative focused and efÞ cient, its scope was limited to research areas dealing with the recent past, present and future of ocean acidiÞ cation. We hope this initiative will stimulate similar activities in research foci that are not covered in this guide, including palaeoceanography.

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7Guide to best practices for ocean acidiÞ cation research and data reportingTable of contents List of acronyms and abbreviations . 11Contributing authors 131The carbon dioxide system in seawater: equilibrium chemistry and measurements 171.1Introduction .171.2Basic chemistry of carbon dioxide in seawater .201.3The deÞ nition and measurement of pH in seawater 271.4Implications of other acid-base equilibria in seawater on seawater alkalinity ..311.5Choosing the appropriate measurement techniques 321.6Conclusions and recommendations .381.7References 392Approaches and tools to manipulate the carbonate chemistry 412.1Introduction .412.2Approaches and methodologies .412.3Strengths and weaknesses .452.4Potential pitfalls and suggestions for improvements ..462.5Data reporting .502.6Recommendations for standards and guidelines ..512.7References 513Atmospheric CO2 targets for ocean acidiÞ cation perturbation experiments 533.1Introduction .533.2Approaches and methodologies .553.3Strengths and weaknesses .623.4Potential pitfalls .623.5Suggestions for improvements ..633.6Data reporting .633.7Recommendations for standards and guidelines ..633.8References 644Designing ocean acidiÞ cation experiments to maximise inference ..674.1Introduction .674.2The sampling universe 674.3Experimental design 694.4Statistical analyses 724.5Recommended texts for further reading 794.6Recommendations for standards and guidelines ..794.7References 795Bioassays, batch culture and chemostat experimentation .815.1Introduction .815.2Approaches and methodologies .825.3Strengths and weaknesses .905.4Potential pitfalls .915.5Suggestions for improvements ..915.6Data reporting .925.7Recommendations for standards and guidelines ..925.8References 92

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86Pelagic mesocosms 956.1Introduction .956.2Approaches and methodologies .976.3Strengths and weaknesses ..1046.4Potential pitfalls and suggestions for improvements 1046.5Data reporting ..1076.6Recommendations for standards and guidelines 1086.7References .1087Laboratory experiments and benthic mesocosm studies ..113 7.1Introduction 113 7.2Approaches and methodologies 114 7.3Strengths and weaknesses 115 7.4Potential pitfalls 117 7.5Suggestions for improvements .119 7.6Data reporting 119 7.7Recommendations for standards and guidelines 1207.8References .1218 In situ perturbation experiments: natural venting sites, spatial/temporal gradients in ocean pH, manipulative in situ p(CO2) perturbations ..1238.1Introduction ..1238.2Approaches and methodologies ..1268.3Strengths and weaknesses ..1298.4Potential pitfalls ..1328.5Suggestions for improvement ..1338.6Data reporting ..1338.7Recommendations for standards and guidelines 1338.8References .1349Studies of acid-base status and regulation ..1379.1Introduction ..1379.2Fundamentals of acid-base regulation .1389.3Measurement of pH, total CO2 and non-bicarbonate buffer values ..1419.4Compartmental measurements: towards a quantitative picture ..1569.5Overall suggestions for improvements 1599.6Data reporting ..1609.7References .16010Studies of metabolic rate and other characters across life stages 16710.1Introduction ..16710.2DeÞ nition of a frame of reference: studying speciÞ c characters across life stages ..16710.3Approaches and methodologies: metabolic studies ..17210.4Study of early life stages 17510.5Techniques for oxygen analyses .17610.6Overall suggestions for improvements 17710.7Data reporting ..17710.8Recommendations for standards and guidelines 17710.9References .17811Production and export of organic matter .18111.1 Introduction ..18111.2 Approaches and methodologies ..18211.3 Strengths and weaknesses ..186

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911.4 Potential pitfalls ..18811.5 Suggestions for improvements 19111.6 Data reporting ..19111.7 Recommendations for standards and guidelines 19411.8 References .19512Direct measurements of calciÞ cation rates in planktonic organisms.201 12.1Introduction ..20112.2Approaches and methodologies ..20112.3Strengths and weaknesses ..20612.4Potential pitfalls ..20812.5Suggestions for improvement ..20812.6Data reporting ..20812.7Recommendations for standards and guidelines 20912.8References .20913Measurements of calciÞ cation and dissolution of benthic organisms and communities .21313.1Introduction ..21313.2Approaches and methodologies ..21313.3CalciÞ cation ..21413.4Dissolution .22413.5Strengths and weaknesses ..22613.6Potential pitfalls ..22713.7Suggestions for improvement ..22713.8Data reporting ..22713.9Recommendations for standards and guidelines 22813.10References .22814Modelling considerations 23314.1Introduction ..23314.2Approaches and methodologies ..23414.3Strengths and weaknesses ..23614.4Potential pitfalls ..23714.5Suggestions for improvements 23814.6Data reporting ..23914.7Recommendations for standards and guidelines 23914.8References .23915 Safeguarding and sharing ocean acidiÞ cation data. 24315.1Introduction ..24315.2Sharing ocean acidiÞ cation data .24315.3Safeguarding ocean acidiÞ cation data .24515.4Harmonising ocean acidiÞ cation data and metadata 24615.5Disseminating ocean acidiÞ cation data and metadata .24715.6Reporting data and metadata 24815.7Avoiding pitfalls and addressing challenges 25515.8Recommendations for standards and guidelines 25715.9References .258

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