Over-determined charbonate chemstry dataset from different kinds of manipulation (TA, DIC) and water types (natural and artificial seawater)@en

The growing field of ocean acidification research is concerned with the investigation of organism responses to increasing pCO2 values. One important approach in this context is culture work using seawater with adjusted CO2 levels. As aqueous pCO2 is difficult to measure directly in small-scale experiments, it is generally calculated from two other measured parameters of the carbonate system (often AT, CT or pH). Unfortunately, the overall uncertainties of measured and subsequently calculated values are often unknown. Especially under high pCO2, this can become a severe problem with respect to the interpretation of physiological and ecological data. In the few datasets from ocean acidification research where all three of these parameters were measured, pCO2 values calculated from AT and CT are typically about 30% lower (i.e. ~300 µatm at a target pCO2 of 1000 µatm) than those calculated from AT and pH or CT and pH. This study presents and discusses these discrepancies as well as likely consequences for the ocean acidification community. Until this problem is solved, one has to consider that calculated parameters of the carbonate system (e.g. pCO2, calcite saturation state) may not be comparable between studies, and that this may have important implications for the interpretation of CO2 perturbation experiments.日益发展的海洋酸化研究领域，聚焦于探究生物机体对二氧化碳分压（pCO2）升高的响应。该领域的一项重要研究方法为使用经二氧化碳水平调节的海水开展培养实验。由于在小型实验中难以直接测定水相二氧化碳分压，目前通常通过碳酸盐体系的另外两个实测参数（多为总碱度(AT)、总无机碳(CT)或pH值）间接计算得到。遗憾的是，实测值与后续计算值的整体不确定性往往未被明确界定。尤其在高二氧化碳分压条件下，这一问题会严重干扰生理与生态数据的解读。在已公开的少量海洋酸化研究数据集中，当三个碳酸盐体系参数均被实测时，由总碱度(AT)与总无机碳(CT)计算得到的二氧化碳分压值，通常比由总碱度(AT)与pH值或总无机碳(CT)与pH值计算得到的结果低约30%（例如目标分压为1000微大气压时，计算结果约为300微大气压）。本研究对这类差异及其对海洋酸化研究领域的潜在影响进行了阐述与讨论。在该问题得到解决之前，学界需意识到：不同研究中计算得到的碳酸盐体系参数（如二氧化碳分压、方解石饱和状态）可能不具备可比性，这或将对二氧化碳扰动实验的结果解读产生重要影响。