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

智力上的功绩。不断加剧的海洋酸化和海洋表面温度的升高可能会对海洋浮游生物群落结构和群落一级的过程产生重大影响。然而，由于微生物组合的巨大分类复杂性以及目前可用于检验特定假说的方法学和实验工具的局限性，我们预测特定反应的能力仍然有限。研究因二氧化碳/温度变化而产生的群落水平影响的研究通常涉及短期田间培养，使生物处于模拟的“温室”条件下。理解全球气候变化的一个中心问题是，在短期操作期间在群落中观察到的趋势和模式是否可以外推到完全适应的浮游生物群落在十年或更长时间尺度上的反应。这项研究计划的具体目标是：1)研究原生生物群落如何在半连续的野外培养实验中随着海水CO2浓度和温度的增加而重建，以及2)评估在野外实验中从环境或增加的CO2和温度处理中分离出来的优势藻种是否会在相同条件下重新确立驯化实验室培养竞争研究中的优势。在我们的实验治疗中，我们将使用基于图像的方法(流式细胞术、FlowCAM和显微镜)结合最先进的分子工具(DNA指纹)来跟踪天然蛋白组合的群落结构的变化。分子方法已经开始揭示海洋微生物令人难以置信的高度多样性，并引发关于微生物“稀有生物圈”无处不在的辩论；也就是说，大量物种的存在在微生物总数中所占的比例非常小，在优势微生物中所占的比例要小得多。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将选择其中一些在环境条件下不明显的成员。这种实验方法的独特之处在于，将涵盖整个自然微生物组合的现场培养与一系列实验室培养竞争试验相结合，这些试验集中在长期驯化后的同一组藻类上，以评估检验二氧化碳和温度变化的短期实验的有效性。首先，将进行野外孵化实验，以表征环境和未来二氧化碳/温度条件下原生动物群落结构的变化。其次，克隆藻类菌株将从当今和温室处理的优势类群中分离出来，并在它们“喜欢的”二氧化碳/温度条件下长期培养。最后，这些驯化菌株的混合物将相互竞争，重新检查它们对环境和温室条件的反应，并将它们与未驯化的野外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在南加州大学博士研究的重点，本科生将参与现场和实验室工作。这项研究的结果将被纳入关于微生物多样性和全球气候变化的课程计划。计划在项目网站上传播数据和成果。该项目中的私人投资机构还参与了一个正在进行的、创新的、由NSF资助的计划(海洋科学教育卓越中心；COSEE-WEST)，该计划的重点是教师个人参与定制框架，以便与K-12教师建立有效的联系，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.