Effects of Ocean Acidification on Nutrient Availability and Requirements in Phytoplankton

大气CO2的持续积累对海洋的最确定的影响是CO2浓度、溶解CO2活性（[CO2]）的增加和表面沃茨pH值的降低。这种“酸化”可能会影响浮游植物营养物质的可用性以及生物体的生理机能。因此，从生物学的角度来看，二氧化碳增加所引起的海洋化学变化将与物理变化相互作用，预计物理变化将改变营养物质向海面的输入。对初级生产的净影响和有机物向深海的输出代表了对大气CO2增加的潜在反馈。在这个项目中，普林斯顿大学的研究人员将量化[CO2]持续增加和表层海水pH值下降对海洋浮游植物中宏量和微量营养素的需求和可用性的影响，以及生物体生长和元素组成的变化。根据我们对浮游植物生理学的了解和一些初步数据，[CO2]的增加可能会提高生物体利用Fe和N的效率，这是海洋中两种主要的限制性营养素。pH值的降低可能会改变必需微量金属的可用性，特别是Fe，通过改变它们在介质中的化学形态，并通过降低胞外酶的活性来改变从有机来源中吸收大量营养素。为了揭示海洋酸化对浮游植物的复杂影响，他们将首先根据三种不同的假设进行三种研究途径：1）酸化降低了浮游植物细胞对铁的吸收速率，同时提高了它们对铁的利用效率（2）酸化增加了氮限制型浮游植物的C：N比，这是因为酸化提高了N的利用效率和富C化合物的储存量;酸化降低了浮游植物利用有机磷源的能力，这是由于碱性磷酸酶的比活性降低和锌的有效性降低。工作计划包括相互加强的实验室和实地实验，以检验各种假设，阐明潜在的生物化学机制，从而可以推断结果。进一步的工作将取决于初步结果。更广泛的影响：该项目针对的是一个社会非常关注的问题，因此，研究结果预计将引起广泛的兴趣。除了通常的研究和教育活动，这是自然嵌入这样一个项目，一个具体的目标是加强科学界内外更广泛的科学理解和教育。通过多方面的合作，该项目将有助于在对二氧化碳和海洋浮游植物之间相互作用的各个方面感兴趣的不同社区之间建立桥梁-从建模者和航海海洋学家到藻类生理学家和生物化学家。该项目的主题还应有效地开展旨在改善科学学校教师教育的外展活动，并为他们提供材料以提高教学有效性。一个实习项目将为来自新泽西社区学院的学生提供实践研究经验。

The most certain effect on the ocean of the ongoing build up of atmospheric CO2 is an increase in the CO2 concentration, dissolved CO2 activity ([CO2]), and a decrease in the pH of surface waters. This "acidification" will likely affect the availability of nutrients to phytoplankton as well as the physiology of the organisms. Thus, from a biological point of view, the chemical changes in ocean chemistry brought about by the CO2 increase will interact with the physical changes, which are expected to modify the input of nutrients to the surface. The net effect on primary production and the export of organic matter to the deep represents a potential feedback to the increase in atmospheric CO2.In this project, researchers at Princeton University will quantify the effects of the ongoing increase in [CO2] and the decrease in pH in surface seawater on the requirements and availability of macro- and micro-nutrients in marine phytoplankton, and the resulting changes in the growth and elemental composition of the organisms. Based on what we know of the physiology of phytoplankton and some preliminary data, an increase in [CO2] likely to increase the efficiency with which the organisms utilize Fe and N, two of the principal limiting nutrients in the ocean. A decrease in pH is likely to change the availability of essential trace metals, particularly Fe, by changing their chemical speciation in the medium, and the uptake of macro-nutrients from organic sources by decreasing the activity of extracellular enzymes.To unravel the complex effects of ocean acidification on phytoplankton they will pursue initially three avenues of research based on three distinct hypotheses: 1) acidification lowers the rate of Fe uptake by phytoplankton cells and simultaneously increases their Fe use efficiency (the former because of low pH, the latter because of high [CO2]); 2) acidification increases the C:N ratio of N-limited phytoplankton because of an increase in N use efficiency and the storage of C-rich compounds; and 3) acidification decreases the ability of phytoplankton to use organic sources of P because of a decrease in the specific activity of alkaline phosphatase and in Zn availability for synthesis of the enzyme. The plan of work consists of mutually reinforcing laboratory and field experiments to test the various hypotheses and to elucidate the underlying biochemical mechanism so that the results can be extrapolated. Further work will depend on initial results. Broader Impacts: This project addresses an issue of great concern to society and the results of the research are thus expected to generate wide interest. Beyond the usual research and educational activities that are naturally embedded in such a project, a specific goal is to enhance scientific understanding and education more broadly within and outside the scientific community. Through multiple collaborations, this project will serve to bridge different communities interested in diverse aspects of the interactions between CO2 and marine phytoplankton-- from modelers and seagoing oceanographers to algal physiologists and biochemists. The topic of this project should also be effective for outreach activities designed to improve the education of science school teachers and provide them with material to enhance the effectiveness of their teaching. An internship program will provide hands-on research experience to students from community colleges in New Jersey.