Experimental studies to understand and evaluate acclimation of marine plankton assemblages to increased CO2 and temperature.

智力优势。海洋不断酸化和海表温度上升可能会对海洋浮游生物群落结构和群落一级的进程产生重大影响。然而，我们预测特定反应的能力仍然是有限的，因为微生物组合的巨大分类复杂性和目前可用于测试特定假设的方法和实验工具的局限性。研究社区水平的影响，由于不断变化的CO2/温度制度往往涉及短期的实地培养，生物体模拟“温室”条件。理解全球气候变化的一个核心问题是，在短期操作期间观察到的群落趋势和模式是否可以外推到十年或更长时间尺度上完全适应的浮游生物群落的反应。该研究计划的具体目标是：1）在半连续的野外培养实验中，研究原生生物群落如何对海水CO2浓度和温度的增加作出反应，和2）评估在野外实验中从环境或增加的CO2和温度处理中分离的优势藻类物种是否会重新形成，在驯化的实验室培养竞争研究中，在相同条件下确立优势。在我们的实验处理中，自然原生生物群落结构的变化将采用基于图像的方法（流式细胞术，FlowCAM和显微镜）结合最先进的分子工具（DNA指纹）。分子方法已经开始揭示海洋微生物的令人难以置信的高度多样性，并激发了关于微生物“稀有生物圈”无处不在的辩论;也就是说，存在着大量的物种，这些物种在微生物总丰度中所占的百分比非常小，占主导地位的百分比要小得多。人们对这些稀有物种的生态意义知之甚少，研究人员假设二氧化碳和温度的变化会选择其中一些在环境条件下不显眼的成员。这种实验方法的独特之处在于结合使用了包括整个自然微生物组合的现场培养，以及一系列实验室培养竞争试验，这些试验集中在延长驯化后的相同藻类群体上，以评估短期实验的有效性，这些实验研究了不断变化的CO2和温度。首先，将进行实地孵化实验，以描述环境和未来CO2/温度制度下原生生物群落结构的变化。第二，克隆藻株将被分离出占主导地位的类群在当今和温室的治疗，并培养了较长的时间在他们的“首选”的CO2/温度条件下。最后，这些驯化菌株的混合物将相互竞争，以重新检查它们对环境和温室条件的反应，并将其与未驯化的田间培养实验中观察到的反应进行比较。两名研究生将把这个项目作为他们博士学位的重点。研究在南加州大学，本科生将参与实地和实验室工作。这项研究的结果将纳入关于微生物多样性和全球气候变化的课程计划。计划在一个项目网站上传播数据和结果。该项目中的PI还参与了一个持续的，创新的，NSF资助的计划（海洋科学教育卓越中心; COSEE-West），该计划侧重于教师在自定义框架中的个人参与，以允许与K-12教师的有效联系，从而改善南加州贫困地区的数学和科学教育。

Intellectual Merit. Progressing ocean acidification and increasing sea surface temperature may significantly impact marine plankton community structure and community-level processes. Yet, our ability to predict specific responses is still limited because of the tremendous taxonomic complexity of microbial assemblages and the limitations of the methodological and experimental tools presently available to test specific hypotheses. Research to study community level effects due to a changing CO2/temperature regime often involve short-term field incubations that subject organisms to simulated 'greenhouse' conditions. A central question for understanding global climate change is whether the trends and patterns that are observed in communities during short-term manipulations can be extrapolated to the responses of fully acclimated plankton communities over decadal or longer timescales. The specific objectives of this research program are: 1) to examine how protistan communities restructure in response to increased seawater CO2 concentrations and temperature in semi-continuous field incubation experiments, and 2) to evaluate if the dominant algal species that are isolated from either ambient or increased CO2 and temperature treatments in field experiments will re-establish dominance under the same conditions in acclimated laboratory culture competition studies. Changes in community structure of natural protistan assemblages in our experimental treatments will be followed using image-based methods (flow cytometry, FlowCAM and microscopy) in combination with state-of the art molecular tools (DNA fingerprinting). Molecular approaches have begun to reveal an incredible high diversity for marine microbes and stimulate debate in regard to the ubiquitous presence of a microbial 'Rare Biosphere'; that is, the presence of a huge number of species that are present at extremely small percentages of the total abundance of microbes, among a much smaller percentage of dominant ones. Little is known about the ecological significance of these rare species, and the investigators hypothesize that change in CO2 and temperature will select for some of these members that are inconspicuous under ambient conditions. The unique aspect of this experimental approach is the combined use of field incubations that encompass entire natural microbial assemblages, with a series of laboratory culture competition trials that focus on the same groups of algae after extended acclimation, to evaluate the validity of short-term experiments that examine changing CO2 and temperature. First, field incubation experiments will be conducted to characterize changes in protistan community structure under ambient and future CO2/temperature regimes. Second, clonal algal strains will be isolated from dominant taxa in present day and greenhouse treatments, and cultivated for extended periods under their 'preferred' CO2/temperature conditions. Finally, mixtures of these acclimated strains will be competed against each other, to re-examine their responses to ambient and greenhouse conditions and compare them to the responses observed in the unacclimated field incubation experiments.Broader Impacts. Two graduate students will make this project the focus of their Ph.D. research at USC, and undergraduate students will be involved in the field and laboratory work. Results from this research will be incorporated in lesson plans on microbial diversity and global climate change. Dissemination of data and results is planned on a project website. The PIs in this project also participate in an on-going, innovative, NSF-funded program (Centers for Ocean Science Education Excellence; COSEE-West) which focuses on personal involvement of faculty in a custom framework to allow an effective connection with K-12 teachers, thus improving math and science education in disadvantaged parts of Southern California.