BEE: Testing the evolutionary responses of mixotrophs to future ocean conditions

BEE：测试混合营养生物对未来海洋条件的进化反应

基本信息

批准号：
1851194
负责人：
Holly Moeller
金额：
$ 53.61万
依托单位：
University of California-Santa Barbara
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2019
资助国家：
美国
起止时间：
2019-05-15 至 2023-04-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1851194&HistoricalAwards=false
关键词：
BEE Testing evolutionary responses mixotrophs

项目摘要

Aquatic ecosystems host a wide variety of single-celled, microscopic organisms. Many of these species live near the surface of the water, where they grow and reproduce using different metabolic strategies that shape their place in the marine food web. For example, biologists have traditionally grouped planktonic microbes into either primary producers (which use photosynthesis to create new organic matter) or heterotrophs (which eat organic matter - such as the bodies - produced by other organisms). However, a large number of species are actually mixotrophic: they "mix" these two forms of metabolism by simultaneously conducting photosynthesis and eating smaller cells, including bacteria. Furthermore, many mixotrophs are metabolically flexible: they may rely more or less on each source of metabolism depending on environmental conditions. Because photosynthesis (which takes carbon out of the atmosphere and locks it into organic matter) and heterotrophy (which respires organic matter back into carbon dioxide) control whether or not oceanic food webs act as carbon sinks (having a net removal of carbon dioxide from the atmosphere), understanding mixotroph metabolism is critical to predicting the effects of marine plankton on atmospheric carbon. This project advances understanding of mixotroph metabolism by quantifying the extent to which mixotrophs can alter their reliance on photosynthesis over short and long timescales. The project tests how quickly mixotrophs can adapt to both warmer and colder water conditions, and how these adaptations alter their role in the carbon cycle. Researchers - including graduate students, a postdoctoral researcher, and undergraduate trainees - will measure the physiological responses of experimentally evolved mixotrophs and use mathematical models to connect these changes to global oceanic carbon cycling. As data are collected, they are shared with the public through outreach seminars, annual open house events, and weekly scientific presentations at the local Santa Barbara Museum of Natural History.In order to predict biologically mediated feedbacks in the climate system, we must understand how marine plankton will respond to future ocean conditions. While a number of studies have sought to quantify the potential evolutionary response of phytoplankton, much less is known about the impacts of shifting conditions (e.g., increased temperature) on mixotrophs. What data are available suggest that mixotrophs may modulate a positive climate feedback loop: when warmed, mixotrophs become more heterotrophic, thus reducing their contribution to the biological pump and enhancing local respiration of organic carbon. Warming may also result in reductions in cell size, reducing sinking fluxes and carbon export from the upper ocean. Furthermore, because the predicted increase in oceanic stratification is expected to favor mixotrophs, their metabolic responses may be increasingly significant to understanding the global carbon cycle. The PI of this project is experimentally evolving mixotrophs under a range of temperature conditions in a fully factorial design that also manipulates the availability of light (photosynthesis) and prey (heterotrophy). She quantifies the carbon budget, grazing activity, nutrient content, and grazer palatability of evolved lineages in order to estimate the impact of any observed adaptations on carbon cycling. Specifically, the investigator asks how evolved lineages compare to ancestral lineages in their ability to tolerate altered thermal conditions, and connects differences in fitness to shifts in reliance on photosynthesis versus heterotrophy. Simultaneously, she incorporates a mixotrophy module into a global ocean biogeochemistry model, allowing the quantification of the impact of mixotrophs with either contemporary or evolved physiological traits. This work will provide some of the first known data on mixotroph plastic and evolutionary responses, and allow the scaling of these responses to their potential impacts on upper ocean biogeochemistry.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.

水生生态系统拥有多种单细胞微观生物。这些物种中有许多生活在水面附近，它们使用不同的代谢策略生长和繁殖，这些策略塑造了它们在海洋食品网中的位置。例如，传统上，生物学家将浮游生物微生物分组为主要生产者（使用光合作用来创建新的有机物）或异育（它们吃有机物，例如由其他生物体生产的物体）。然而，许多物种实际上是造成多种物种的：它们通过同时进行光合作用和食用较小的细胞（包括细菌）来“混合”这两种形式的代谢。此外，许多混合营养在代谢上是灵活的：根据环境条件，它们可能或多或少地依赖于每种代谢来源。 Because photosynthesis (which takes carbon out of the atmosphere and locks it into organic matter) and heterotrophy (which respires organic matter back into carbon dioxide) control whether or not oceanic food webs act as carbon sinks (having a net removal of carbon dioxide from the atmosphere), understanding mixotroph metabolism is critical to predicting the effects of marine plankton on atmospheric carbon.该项目通过量化混合营养的程度可以改变其对光合作用的依赖，从而提高对混合营养代谢的理解。该项目测试了混合营养的速度能够适应较温暖和较冷的水条件，以及这些适应如何改变其在碳循环中的作用。研究人员 - 包括研究生，博士后研究人员和本科学员 - 将衡量实验发展的混合营养的生理反应，并使用数学模型将这些变化与全球海洋碳循环联系起来。随着数据的收集，它们通过外展研讨会，年度开放式活动和每周的科学演讲与公众共享，并在当地的圣塔芭芭拉自然历史博物馆进行。为了预测气候系统中的生物学介导的反馈，我们必须了解Marine Plankton将如何应对未来的海洋条件。尽管许多研究试图量化浮游植物的潜在进化反应，但对转移条件（例如温度升高）对混合营养的影响的影响少得多。可用的数据表明，混合营养可能会调节积极的气候反馈循环：当变暖后，混合营养物会变得更加异性，从而减少了它们对生物泵的贡献并增强了有机碳的局部呼吸。变暖还可能导致细胞尺寸减少，减少上海洋的下沉通量和碳出口。此外，由于预计海洋分层的预测增加有利于混合营养，因此它们的代谢反应对于理解全球碳循环可能越来越重要。该项目的PI在实验中是在一系列温度条件下实验发展的，在完全阶乘设计的范围内，还可以操纵光（光合作用）和猎物（异性营养）的可用性。她量化了进化谱系的碳预算，放牧活动，养分含量以及放牧的可口性，以估计任何观察到的适应对碳循环的影响。具体而言，研究者询问了进化的谱系与祖先谱系的耐受性热条件的能力相比，并将适应度的差异与依赖于光合作用与异性营养的转移联系起来。同时，她将混合植物模块纳入了全球海洋生物地球化学模型，从而量化了具有当代或进化的生理特征的混合营养的影响。这项工作将提供一些有关混合营养塑料和进化反应的第一个已知数据，并允许这些响应对它们对上海生物地球化学的潜在影响的缩放。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛影响的审查标准来通过评估来通过评估来支持的。