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

初级生产者的光合作用是地球生态系统的基础。在陆地上，主要生产者是植物，但在海洋中，大多数光合作用是由单细胞微生物完成的。值得注意的是，这些微小的植物中有许多也是捕食其他微生物的捕食者。这些生物是海洋中的金星捕蝇器，因其混合营养而被称为“混合营养生物”。之前的研究比较了混合营养生物和自养生物(只起植物作用的生物体)，发现当海水表面有一个明显的暖层(称为层化)时，混合营养生物更丰富。混养动物数量的增加可能会对海洋生态系统产生重大影响，因为随着地球变暖，海洋在全球范围内正变得更加分层。由于混合营养生物可能在未来的海洋中发挥更大的作用，研究混合营养是否会改变生态系统的工作方式是至关重要的。在这个项目中，研究人员将研究混合营养如何改变通过食物网的能量和营养物质的流动，以及这可能对未来的海洋造成什么后果。这些问题对于社会对生物圈的依赖非常重要，因为更具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。该项目将支持一名博士后、两名研究生和本科生在综合生物多样性科学方面的培训，该科学包括野外、实验室和建模组件。关于混合营养体及其在海洋中的作用的想法将被发展为夏威夷科学推广活动的教育游戏，PI将通过UH Manoa的项目招募本科生，这些项目服务于太平洋岛民和其他代表性不足的群体。该项目的具体目标是量化普通混合营养消费者的功能多样性，并将它们与不进行光合作用的普通异养生物进行比较。研究人员将使用现场和实验室实验来询问不同的混合养殖体和异养体对最常见的细菌猎物：蓝藻原氯球菌、异养细菌分支SAR11(Pelagibacter)和异养细菌家族红杆菌是否有不同的摄食。他们将利用实验室对不同的菌株进行实验，以询问混养-异养藻类的光谱是否会导致捕食率、食物链上的营养物质转移以及浮游生物的元素组成发生一致的变化。他们将分析全球调查数据，以询问混合营养和异养类群的相对丰度如何随着层化和其他环境梯度的增加而变化。最后，他们将使用数学模型来评估群落结构模式是否与基于实验结果的理论预测一致。总而言之，这项工作将量化一组全球重要但研究较少的微生物的功能生物多样性，预测群落和生态系统将如何因全球变暖而改变，并促进对微生物食物网的理论理解。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.