Collaborative Research: Diversity and ecological impacts of Antarctic mixotrophic phytoplankton

合作研究：南极混合营养浮游植物的多样性和生态影响

• 批准号: 1744663
• 负责人: Rebecca Gast
• 金额: $ 27.75万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-09-01 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1744663&HistoricalAwards=false
• 关键词: Collaborative; Research; Diversity; ecological; impacts

Traditional models of oceanic food chains have consisted of photosynthetic algae (phytoplankton) being ingested by small animals (zooplankton), which were ingested by larger animals (fish). These traditional models changed as new methods allowed recognition of the importance of bacteria and other non-photosynthetic ?protozoa? in more complex food webs. More recently, the wide-spread existence of mixotrophs (organisms that can both photosynthesize and ingest food particles) and their importance as microbial predators has been recognized in many oceanographic areas. In the Southern Ocean, the only two surveys of mixotrophs have suggested that there may be seasonal differences in their importance as predators. During the long polar night (winter), the ability of mixotrophs to ingest particulate food may aid in their survival thus ensuring a sufficient population in spring to support a phytoplankton bloom once photosynthesis rates can increase. Thus mixotrophs may provide a critical early food source upon which zooplankton and larger animals depend on for growth and reproduction. This project will advance understanding of mixotroph diversity and their ecological impact within the Southern Ocean microbial food web. Specifically, efforts will be focused on mixotrophy in the western Antarctica peninsula region during the austral spring and autumn when there are likely to be changes in the relative importance of photosynthesis and ingestion to mixotrophs. The project will provide research opportunities for undergraduate and graduate students and a post-doctoral researcher. There will be real-time outreach from the Southern Ocean to the public via blogs and interviews, and to high school art students through an established program that blends science and art education. Despite traditional views of protists as either "phototrophic" or "heterotrophic," there are many photosynthetic protists that consume prey (mixotrophy). Mixotrophy is a widespread phenomenon in aquatic systems and phytoplankton groups with known mixotrophic species, notably chrysophytes, cryptophytes, prymnesiophytes, prasinophytes and dinoflagellates, are present and often abundant in Antarctic waters. However, in the Southern Ocean, the presence of mixotrophic phytoflagellates has been surveyed only twice: in the Ross Sea during Austral spring 2008 and summer 2011. The primary goals of the project are to gain better understanding of mixotroph diversity and their ecological impact with respect to the Southern Ocean microbial food web. The contribution of mixotrophs to primary production and bacterial consumption is likely linked to the taxonomic composition of the community and the abundance of particular species. Abundances of novel mixotrophic species will be evaluated via qPCR, which will be coupled with assessments of rates of feeding and photosynthesis with the goal of describing how active mixotrophs direct the movement of carbon through food webs. These experiments will help the determination of how viable and widespread mixotrophy is as a nutritional strategy in polar waters and give direct information on the currently unknown diversity of mixotrophic taxa under different environmental conditions occurring in austral spring and autumn. Furthermore, the methods will simultaneously yield information on the whole communities of protists - mixotrophic, phototrophic and heterotrophic. In addition, a method to examine aspects of the taxonomic and functional diversities of the bacterivorous/mixotrophic community will be employed. A thymidine analog (BrdU) will be used to label DNA of eukaryotes feeding on bacteria. The BrdU-labeled eukaryotic DNA will be isolated using immunoprecipitation. High-throughput sequencing of the labeled DNA (bacterivores) versus unlabeled community DNA will determine the diversity of bacterivorous mixotrophs relative to other microeukaryotes. Flow cytometric sorting based on chlorophyll to focus on mixotrophic species. These approaches will elucidate a gap in current knowledge of the influence of microbial interactions in the Southern Ocean under different conditions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

传统的海洋食物链模型包括光合藻类（浮游植物）被小型动物（浮游动物）摄取，而小型动物又被大型动物（鱼类）摄取。这些传统的模型改变了新的方法允许认识到细菌和其他非光合作用的重要性？原生动物？在更复杂的食物网中。最近，混养生物（既能进行光合作用又能摄取食物颗粒的生物）的广泛存在及其作为微生物捕食者的重要性在许多海洋学领域得到了承认。在南大洋，仅有的两项对混合营养体的调查表明，它们作为掠食者的重要性可能存在季节差异。在漫长的极夜（冬季），混合营养体摄取颗粒食物的能力可能有助于它们的生存，从而确保在春季有足够的种群来支持浮游植物的繁殖，一旦光合作用速率可以增加。因此，混合营养生物可能提供了一个关键的早期食物来源，浮游动物和较大的动物依赖于生长和繁殖。该项目将促进对混合营养生物多样性及其在南大洋微生物食物网中的生态影响的了解。具体而言，努力将集中在混合营养在南极洲西部半岛地区在南部的春季和秋季时，可能会有变化的光合作用和摄取的相对重要性，以mixotrophs。该项目将为本科生、研究生和博士后研究人员提供研究机会。通过博客和采访，将有从南大洋到公众的实时外展，并通过一个融合科学和艺术教育的既定计划，以高中艺术学生。尽管传统的观点认为原生生物是“光养”或“异养”的，但有许多光合原生生物消耗猎物（混合营养）。混合营养是水生系统中的一种普遍现象，南极沃茨中存在并经常大量存在已知混合营养物种的浮游植物群体，特别是金藻、隐藻、原生藻、prasinophytes和甲藻。然而，在南大洋，混合营养型植物鞭毛虫的存在只调查了两次：在罗斯海在南极春季2008年和夏季2011年。该项目的主要目标是更好地了解混合营养生物的多样性及其对南大洋微生物食物网的生态影响。混合营养体对初级生产和细菌消耗的贡献可能与群落的分类组成和特定物种的丰度有关。将通过qPCR评估新的兼养物种的丰度，这将与摄食率和光合作用的评估相结合，目的是描述活性兼养生物如何指导碳通过食物网的运动。这些实验将有助于确定如何可行的和广泛的混合营养是作为一种营养策略，在极地沃茨，并提供直接的信息，目前未知的多样性的混合营养类群在不同的环境条件下发生在南方的春季和秋季。此外，这些方法将同时产生关于原生生物的整个群落的信息-兼养、光养和异养。此外，还将采用一种方法来检查食菌/兼养群落的分类和功能多样性。胸苷类似物（BrdU）将用于标记以细菌为食的真核生物的DNA。将使用免疫沉淀分离BrdU标记的真核DNA。高通量测序标记的DNA（bacteriovores）与未标记的社区DNA将确定多样性的bacteriovorous mixotrophs相对于其他微真核生物。基于叶绿素的流式细胞仪分选，专注于兼养物种。这些方法将阐明目前对不同条件下南大洋微生物相互作用影响的认识存在的差距。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。