Collaborative Research: The Great Southern Coccolithophore Belt

智力优势：卫星遥感的最新进展使从太空估计悬浮碳酸钙(颗粒无机碳或“PIC”)成为可能。这种辐射方法在操作上对海洋球虫(甲藻)是特异的，并且足够灵敏，足以量化营养稀少的环状回中的PIC浓度。在MODIS Aqua任务的七年时间里拍摄的悬挂的PIC的全球图像显示，在环绕地球的南大洋次南极前沿附近有一条PIC“大带”。这一特征每年发生在南半球夏季，似乎位于南大洋的高营养、低叶绿素区域。长带的面积约为8800万平方公里，占全球海洋的26%。进入大西洋、印度和太平洋区域大带区的几次航行的证据证实，球虫生物体浓度升高；以前在大西洋区域的工作证实了太平洋岛屿中心的高度光学散射。我们仅有的几个船只观测结果与卫星图像完全一致。在这个项目中，研究人员将在下列科学目标的指导下，系统地研究大带的球石生物体：(A)确定这一带内的球石生物体物种；(B)测量球石生物体和相关的PIC的丰度；(C)测量球石生物体的钙化率；(D)阐明可能限制球石生物体纬度范围的因素(例如层化、温度、常量营养素、痕量金属、放牧)；(E)证明PIC的变异性是否与浅层出口通量有关；(F)确定PIC生产的变异性如何与二氧化碳、总碱度和溶解无机碳收支有关；以及(G)审查短期海洋酸化对球石生物体生长和方解石溶解的影响。这项研究将包括在南半球的夏天，沿着50条S平行线航行，以采样长城带。调查人员将结合使用正在进行的地面采样(主要是光学和水文学)和垂直站点剖面(使用CTD/玫瑰花结和大容量潜水泵)来处理与上述目标有关的假设。巡航航迹将阐明大带的纬向和经向变化。受控的CarBoy孵化实验将研究未来各种情况下海洋酸化对球石菌体生长和溶解的影响。稀释实验将解决与放牧有关的死亡率和溶解问题。受控的金属添加孵化将侧重于球石发酵体的潜在铁、锌和钴限制，或与二氧化硅可用性相关的硅藻的竞争。拟议的实地观测和金属添加实验将提供有关全球生物地球化学背景下大带现状的重要信息。就南大洋球藻在未来酸化海洋中的命运而言，即将进行的海洋酸化实验更具前瞻性。更广泛的影响：大带在全球范围内的巨大规模表明，它可能在全球生物地球化学和气候变化反馈中发挥重要作用。因此，研究人员预计这项工作将对生物和化学海洋学产生广泛的、变革性的影响。据预测，燃烧化石燃料引起的海洋酸化将在下个世纪使表层海洋的PH值降低0.3个单位，最高可达0.7个单位--到2300年质子浓度将增加5倍。这项研究的一个主要目标是研究海洋酸化对方解石饱和度低的地区(即方解石预计将变为亚饱和的首批地区之一)球石生物体的影响。因此，这些实验的结果将与我们对海洋碳循环的基本理解高度相关。与职业发展和标准II活动有关，该项目包括为缅因州大学或学院的NSF REU本科生提供两次航海实地体验，为他们参加科学会议提供资金。缅因州大学本科生的参与建设了我们沿海农村州的能力，并帮助阻止了严重的人才外流问题，即最优秀的学生离开缅因州，到更富裕、人口更多的州寻找机会。一名教师也将参加巡航(通过NSF赞助的无敌舰队计划)。这位老师将为学生开发关于球藻生物、钙化、出口生产、金属-浮游生物相互作用、海洋酸化和气候变化等主题的学习模块。

Intellectual merit: Recent advances in satellite remote sensing enable estimation of suspended calcium carbonate (particulate inorganic carbon or 'PIC') from space. This radiative approach is operationally specific to marine coccolithophores (Haptophyceae) and sensitive enough to quantify PIC concentrations in oligotrophic gyres. Global images of suspended PIC taken over the seven years of the MODIS Aqua mission show a 'Great Belt' of PIC near the sub-Antarctic front of the Southern Ocean that circles the globe. This feature occurs every year during austral summer and appears to be within the high-nutrient, low chlorophyll region of the Southern Ocean. The area of the Great Belt is ~88 million km2, 26% of the global ocean. Evidence from several cruises into the Great Belt region of the Atlantic, Indian and Pacific sectors has verified elevated concentrations of coccolithophores; previous work in the Atlantic sector verified high optical scattering from PIC. The few ship observations we have are entirely consistent with the satellite views. In this project, the investigators will systematically study the coccolithophores of the Great Belt guided by the following science goals: (a) identify the coccolithophore species within this belt; (b) measure the abundance of coccolithophores and associated PIC; (c) measure coccolithopore calcification rates; (d) elucidate factors that may limit coccolithophore latitudinal range (e.g. stratification, temperature, macronutrients, trace metals, grazing); (e) demonstrate whether the variability in PIC relates to shallow export flux; (f) define how variability in PIC production relates to the pCO2, total alkalinity and dissolved inorganic carbon budgets; and (g) examine the impact of short-term ocean acidification on coccolithophore growth and calcite dissolution. The research will involve cruises along the 50 S parallel to sample the Great Belt, during the austral summer. The investigators will use a combination of underway surface sampling (primarily optical and hydrographic) and vertical station profiles (using CTD/rosette and large volume submersible pumps) to address hypotheses related to the above goals. The cruise track will elucidate both zonal and meridional variability in the Great Belt. Controlled carboy incubation experiments will examine the impact of ocean acidification at various future scenarios on coccolithophore growth and dissolution. Dilution experiments will address grazing-related mortality and dissolution questions. Controlled metal-addition incubations will focus on potential iron, zinc and cobalt limitation of the coccolithophores or competition from diatoms related to silica availability. The proposed field observations and metal-addition experiments will provide important information on the current status of the Great Belt in the context of global biogeochemistry. The ocean acidification experiments to be undertaken are more forward-looking in terms of the fate of the Southern Ocean coccolithophores in a future acidified ocean. Broader impacts: The globally significant size of the Great Belt indicates that it likely plays a major role in global biogeochemistry and climate change feedbacks. Thus, the investigators expect this work to have broad, transformative impacts in biological and chemical oceanography. Ocean acidification from the burning of fossil fuels is predicted to lower the pH of the surface ocean by 0.3 units in the next century and up to 0.7 units - a 5-fold increase in the proton concentration by the year 2300. A major goal of this study is to examine the effects of ocean acidification on coccolithophores in a region of low calcite saturation (i.e., one of the first regions expected to become sub-saturating for calcite). The results of these experiments will therefore be highly relevant to our basic understanding of the marine carbon cycle. Related to career development and Criterion II activities, the project includes field experience on two cruises for NSF REU undergraduates from Maine universities or colleges, providing funds for them to attend a scientific meeting. Participation of undergraduate students from Maine colleges builds capacity in our rural coastal state and helps thwart the serious issue of 'brain drain', in which the best students are leaving Maine to seek opportunity in wealthier, more populated states. A teacher will also participate on the cruises (via the NSF-sponsored ARMADA program). This teacher will develop learning modules for students about such topics as coccolithophores, calcification, export production, metal-plankton interactions, ocean acidification and climate change.