BoCP-Implementation: Functional diversity of the smallest predators in the current and future ocean

初级生物的光合作用是地球生态系统的基础。在陆地上，主要的光合作用产生者是植物，但在海洋中，大多数光合作用是由单细胞微生物进行的。值得注意的是，许多这些微小的“植物”也是捕食其他微生物的掠食者。这些生物是海洋中的捕蝇草，因其混合营养而被称为“混合营养体”。先前的研究将混合营养体与自养生物（只充当植物的生物）进行了比较，发现当海水表面有明显的暖层（称为分层）时，混合营养体更丰富。混合营养菌丰度的增加可能对海洋生态系统产生重大影响，因为随着地球变暖，全球海洋正变得更加分层。由于混合营养生物可能在未来的海洋中发挥更大的作用，因此研究混合营养是否会改变生态系统的工作方式至关重要。在这个项目中，研究人员将研究混合营养如何改变食物网中能量和营养物质的流动，以及对未来海洋的影响。这些问题对于社会对生物圈的依赖很重要，因为一个更加混合营养的未来可能会减轻或加剧气候变化对海洋生产力的影响。本项目将支持培养一名博士后、两名研究生和本科生，研究综合生物多样性科学，包括实地、实验室和建模组成部分。关于混合营养体及其在海洋中的作用的想法将发展成为夏威夷科学推广活动的教育游戏，pi将通过夏威夷大学马诺阿分校的项目招募本科生，为太平洋岛民和其他代表性不足的群体提供服务。该项目的具体目标是量化常见混合营养消费者的功能多样性，并将其与不进行光合作用的常见异养生物进行比较。研究人员将使用原位和实验室实验来询问不同的混合营养体和异养体对最常见的细菌猎物的消耗是否不同：蓝藻原绿球藻、异养细菌分支SAR11 （Pelagibacter）和异养细菌家族红杆菌科。他们将对不同的分离物进行实验室实验，以询问混合营养-异养光谱是否会导致捕食率、营养物质在食物链上的转移以及浮游生物的元素组成的一致变化。他们将分析全球调查数据，以了解混合营养和异养分类群如何随着分层和其他环境梯度的增加而相对丰富地变化。最后，他们将使用数学模型来评估社区结构模式是否与基于实验结果的理论预测一致。总的来说，这项工作将量化全球重要但研究较少的微生物群的功能生物多样性，预测群落和生态系统将如何因全球变暖而变化，并推进对微生物食物网的理论理解。该奖项反映了美国国家科学基金会的法定使命，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。

Photosynthesis by primary producers is the foundation of Earth’s ecosystems. On land the major producers are plants, but in the ocean most photosynthesis is performed by single-celled microorganisms. Remarkably, many of these tiny ‘plants’ are also predators that eat other microbes. These organisms are the Venus flytraps of the sea and are called ‘mixotrophs’ because of their mixed nutrition. Previous research compared mixotrophs to autotrophs (organisms that only act as plants) and found that mixotrophs are more abundant when ocean waters have a distinct warm layer at the surface (called stratification). Such an increase in mixotroph abundance could have significant implications for ocean ecosystems because the oceans are becoming more stratified globally as the planet warms. As mixotrophs will likely play a larger role in the future ocean, it is critical to study whether mixotrophy changes how ecosystems work. In this project the researchers will address how mixotrophy changes the flow of energy and nutrients through food webs, and what the consequences may be for the future ocean. These questions are important for society’s reliance on the biosphere, because a more mixotrophic future could mitigate or exacerbate the effects of climate change on ocean productivity. This project will support the training of a postdoc, two graduate students, and undergraduate students in integrative biodiversity science that includes field, lab, and modeling components. Ideas about mixotrophs and their role in the ocean will be developed into an educational game for science outreach events in Hawai’i, and the PIs will recruit undergraduates through programs at UH Manoa that serve Pacific Islanders and other under-represented groups. The specific goal of this project is to quantify functional diversity among common mixotrophic consumers and compare them to common heterotrophs that do not photosynthesize. The researchers will use in situ and lab experiments to ask whether diverse mixotrophs and heterotrophs differ in their consumption of the most common bacterial prey: the cyanobacterium Prochlorococcus, the heterotrophic bacterial clade SAR11 (Pelagibacter), and the heterotrophic bacterial family Rhodobacteraceae. They will use lab experiments on diverse isolates to ask whether the mixotroph-heterotroph spectrum leads to consistent shifts in predation rates, the transfer of nutrients up the food chain, and the elemental composition of the plankton. They will analyze global survey data to ask how mixotrophic and heterotrophic taxa shift in relative abundance with increasing stratification and other environmental gradients. Finally, they will use mathematical models to assess whether patterns of community structure are consistent with theoretical predictions based on experimental results. In total this work will quantify functional biodiversity among a globally important but poorly studied group of microbes, project how communities and ecosystems will change due to global warming, and advance the theoretical understanding of microbial food webs.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.