Impact of Ocean Acidification on Planktonic Foraminifera in the California Current System During the Last 300 Years

自工业革命开始以来，超过四​​分之一的人为二氧化碳排放已进入全球海洋表层，导致海水 pH 值大幅下降。这种现象被称为海洋酸化（OA），预计在包括美国西海岸在内的沿海地区将变得尤其严重。随着海洋变得更加酸性，海洋钙化者将越来越难以产生贝壳。这可能会对海洋食物网和各种具有重要商业意义的海洋物种产生重要影响。这项研究将首次详细记录过去两个世纪以来加利福尼亚州沿海 OA 的变化。这将通过检查一组称为有孔虫的钙化浮游生物的壳来完成。这些生物体在海面生活并产生贝壳，当生物体死亡时，贝壳会沉入海底。将研究从圣巴巴拉盆地收集的沉积岩芯中的有孔虫壳，以重建过去 200 年来钙化的变化。利用这些结果，根据大气中二氧化碳含量增加的各种情景，可以预测到 21 世纪末钙化将如何继续变化。建模研究表明，加州洋流系统 (CCS) 和相关生态系统已经并将继续特别容易受到海洋酸化 (OA) 的影响。为了检验这一概念，本研究将量化工业革命爆发以来 OA 对 CCS 圣巴巴拉盆地地区浮游有孔虫钙化率的影响。 20 年的圣巴巴拉盆地沉积物捕获时间序列以及该盆地的变化沉积物将用于生成过去 200 年来 CCS 中这组浮游生物钙化变化的几乎每年解析的记录。拟议的研究将分两个阶段进行。首先，沉积物陷阱样本和一致的水柱化学数据将用于校准有孔虫壳形态（面积密度）、壳地球化学（B/Ca）和水柱碳酸盐化学之间的关系。其次，这些形态和痕量金属代理将用于使用 210Pb 测年的 varved 沉积物记录来生成过去两个世纪碳离子浓度变化的两个独立记录。这些来自沉积物的碳离子浓度估计值将与过去两个世纪该参数的模型估计值进行比较。总而言之，沉积物捕集器和岩心样本将为量化 OA 对这一古气候重要浮游生物群钙化的影响提供无与伦比的档案。

More than one-quarter of anthropogenic CO2 emissions produced since the beginning of the Industrial Revolution have been incorporated into the global surface ocean causing large-scale declines in seawater pH. This phenomenon is referred to as ocean acidification (OA) and is predicted to become particularly acute in coastal regions, including the west coast of the US. As the oceans become more acidic, it will become increasingly difficult for marine calcifiers to produce their shells. This may have important consequences for the marine food web and for various commercially important marine species. This study will produce the first detailed record of changes in OA along the coast of California during the last two centuries. This will be accomplished by examining the shells of a group of calcifying plankton called foraminifera. These organisms live and produce their shells at the sea surface, with the shells sinking to the sea floor when the organism dies. Foraminiferal shells from a sediment core collected from Santa Barbara Basin will be studied in order to reconstruct changes in calcification over the last 200 years. Using these results, predictions will be made as to how calcification will continue to change through the end of the 21st century based on various scenarios for increasing atmospheric CO2.Modeling studies suggest that the California Current System (CCS) and associated ecosystem have been and will continue to be particularly vulnerable to ocean acidification (OA). To test this concept, this study will quantify the effect of OA on calcification rates in planktonic foraminifera from the Santa Barbara Basin region of the CCS since the onset of the Industrial Revolution. A 20-year Santa Barbara Basin sediment trap time series, together with the varved sediments from the basin will be used to generate a nearly annually resolved record of changes in calcification for this group of plankton in the CCS for the last 200 years. The proposed research will take place in two phases. First, sediment trap samples and coincident water column chemistry data will be used to calibrate the relationships among foraminiferal shell morphology (area density), shell geochemistry (B/Ca), and water column carbonate chemistry. Second, these morphologic and trace metal proxies will be used to produce two independent records of changing carbon ion concentration for the last two centuries using a 210Pb-dated varved sediment record. These sediment-derived estimates of carbon ion concentration will be compared with model estimates of this parameter for the last two centuries. Taken together, the sediment trap and core samples will provide an incomparable archive for quantifying the impact of OA on calcification in this paleoclimatically important group of plankton.