Marine Diatom-Parasite Relationships in Upwelling Systems

上升流系统中的海洋硅藻与寄生虫的关系

• 批准号: 2149606
• 负责人: Bess Ward
• 金额: $ 39.04万
• 依托单位: Princeton University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-04-01 至 2025-03-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2149606&HistoricalAwards=false
• 关键词: Marine; Diatom; Parasite; Relationships; Upwelling

A recent global survey of surface ocean waters revealed that microbial parasites comprise half of the eukaryotic plankton diversity and suggested that biological interactions, including parasites, play an important role in the ecology of many types of microscopic algae, which are the base of the ocean food web, but not diatoms. Diatoms are among the most abundant microalgae, particularly in upwelling areas where nutrient-rich deep currents feed the ocean's surface and support the world's greatest fisheries. Yet this survey did not investigate high-productivity regions, leaving a significant knowledge gap. Diatoms may be successful in upwelling regions because they evade predators and parasites, but it seems more reasonable that they, like all other microalgae, also have biological enemies. In this study, the researchers use a large set of available samples from upwelling regions to investigate the effect of parasites on the proliferation of diatom communities and resulting primary production. The project supports a graduate student and provides hands-on research experiences for high school and undergraduate college students. The study data are also integrated into courses taught by the principal investigator. The discovery that half of the eukaryotic diversity in the Tara Oceans sequence database belongs to putatively parasitic microbes implies a revolution in our understanding of biological control of primary production. Ecosystem models are only beginning to incorporate the effect of viruses on production and community composition, but eukaryotic parasites add yet another dimension with potentially vast biogeochemical implications. While viral predation is generally thought to divert material flux away from grazers and into the dissolved organic carbon pool, increasing community diversity and microbial biomass, phytoplankton biomass diverted into parasite biomass becomes available to grazers. Experimental determination of parasite activity is difficult in natural systems, so most of the evidence for diversity, abundance, and host interactions of eukaryotic parasites is based on DNA sequence data. The Tara Oceans database suggests that diatoms have very few biotic interactions, leading to a stronger dependence on bottom-up factors (e.g., nutrients). However, this database did not represent high productivity upwelling regions. This project addresses two hypotheses: 1) diatoms in highly productive episodic upwelling systems are involved in host-parasite interactions that can be identified in co-occurrence networks during blooms; and 2) the community composition and abundance of host-parasite pairs vary over the course of the bloom in a manner consistent with density dependence on the host. In this project, abundance, diversity, and dynamics of parasites in upwelling systems are investigated by tag sequencing, metagenomics, and targeted qPCR of diatom-parasite pairs identified from archived samples from diatom-dominated upwelling systems (California Current, Eastern Tropical Pacific), the North Atlantic Spring bloom, and from two mesocosm experiments of diatom blooms induced by inoculation of surface seawater into nitrate-rich Monterey Bay seawater. Biogeochemical parameters (nutrients, primary production, nitrate assimilation, etc.) for those samples are available. In addition, the research team is using the outputs of the bioinformatics analysis in network and time series analysis to discover links among hosts and parasites.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.

最近对表层海洋沃茨的一项全球调查显示，微生物寄生虫占真核浮游生物多样性的一半，并表明包括寄生虫在内的生物相互作用在许多种类的微型藻类的生态学中发挥重要作用，而藻类是海洋食物网的基础，但不是硅藻。硅藻是最丰富的微藻之一，特别是在营养丰富的深海洋流滋养海洋表面并支持世界上最大的渔业的上升流地区。然而，这项调查没有调查高生产率地区，留下了巨大的知识差距。硅藻在上升流区域可能很成功，因为它们逃避捕食者和寄生虫，但似乎更合理的是，它们像所有其他微藻一样，也有生物敌人。在这项研究中，研究人员使用了来自上升流区域的大量可用样本来研究寄生虫对硅藻群落增殖和初级生产的影响。该项目支持研究生，并为高中和本科生提供实践研究经验。研究数据也被纳入主要研究者教授的课程。在塔拉海洋序列数据库中，真核生物多样性的一半属于寄生性微生物，这一发现意味着我们对初级生产生物控制的理解发生了革命。生态系统模型才刚刚开始纳入病毒对生产和社区组成的影响，但真核寄生虫增加了另一个维度，具有潜在的巨大生物地球化学影响。虽然病毒捕食通常被认为将物质流从食草动物转移到溶解的有机碳库，增加群落多样性和微生物生物量，但转化为寄生虫生物量的浮游植物生物量可供食草动物使用。寄生虫活性的实验测定在自然系统中是困难的，因此真核寄生虫的多样性，丰度和宿主相互作用的大多数证据都是基于DNA序列数据。塔拉海洋数据库表明，硅藻几乎没有生物相互作用，导致对自下而上因素的依赖性更强（例如，营养素）。然而，这个数据库并不代表高生产力上升流地区。该项目解决了两个假设：1）硅藻在高生产力的情景上升流系统中参与宿主-寄生虫的相互作用，可以在水华期间的共现网络中识别; 2）宿主-寄生虫对的群落组成和丰度在水华过程中以与密度依赖于宿主一致的方式变化。在这个项目中，丰度，多样性和动态的寄生虫在上升流系统中的标签测序，宏基因组学，和靶向qPCR的寄生虫对鉴定从存档的样品从寄生虫为主的上升流系统（加州海流，热带太平洋东部），北大西洋春季水华，和从两个介观实验硅藻水华接种到表层海水到硝酸盐丰富的蒙特利湾海水诱导。生物地球化学参数（营养物、初级生产、硝酸盐同化等）这些样品都是可用的。此外，该研究小组还将生物信息学分析的结果用于网络和时间序列分析，以发现宿主和寄生虫之间的联系。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。