Collaborative Research: Ecological and biogeochemical role of Rhizaria in the oligotrophic ocean

根瘤菌是大型的单细胞生物，对世界海洋的化学循环做出贡献。常见的Rhizaria（如有孔虫，多囊藻，Phaeodarea）形成的矿物外壳是海洋的锶，二氧化硅和碳预算的一部分，它们代表了至少5.2%的海洋生物碳库在表面区。更好地了解存在的根瘤菌群，它们的生物量以及它们的种群在不同海洋深度的变化对于模拟海洋营养循环至关重要，但对于地球上最大的生物群落之一的大型根瘤菌，这些信息解决得很差或缺乏，中央，低营养海洋环流。这个合作项目涉及一个早期职业和更成熟的研究人员团队，提供了开发Rhizaria对深海营养物质下沉的贡献模型所需的测量，并增加了我们对营养物质如何在海洋中移动以及不断变化的环境条件如何影响这些周期的理解。它正在生成可供海洋学研究人员使用的大型数据集，并为本科生、研究生和高中生提供以海洋学、生物学和数据科学为主题的体验式学习机会。这项研究提供了1）大大改进的贫营养海洋中根瘤菌总生物量的估计，2）根瘤菌垂直分布和环境生态位特征的新测量，3）测量根瘤菌生物量和群落组成的季节变化，4）确定根瘤菌种群季节和空间变化的环境驱动因素，以及5）基于模型估计根瘤菌对进入深海的垂直通量的贡献。研究人员正在使用尼斯金瓶采样，颗粒凝胶陷阱，网拖和尖端的原位成像（使用水下视觉轮廓仪，UVP 5-DEEP）的组合，以绕过其他采样方法的限制，以准确估计根瘤菌生物量。取样的深度范围很广（0- 1 200米），每月一次，并与作为百慕大大西洋时间序列研究一部分收集的各种其他海洋学测量数据一起进行。UVP图像数据集成与分子鉴定的根瘤菌使用社区元条形码，ZooSCAN成像，条形码的个人根瘤菌收集的网拖和凝胶陷阱与UVP铸件。研究人员正在使用大小特定的元素分析的根瘤菌和季节性和垂直明确的估计根瘤菌生物量模型根瘤菌垂直通量的贡献。沿着百慕大大西洋时间序列和海洋通量方案收集的数据，正在将关于根瘤菌的新数据纳入碳和营养物转移到深海的模型。该模型估计了根瘤菌可能影响碳循环的三种方式-通过以颗粒通量为食，通过为海洋雪提供压舱物以及直接下沉-并显示了这些可能在空间和时间上的变化。该项目由生物海洋学、化学海洋学和激励竞争研究的既定计划（EPSCoR）共同资助。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。

Rhizaria are large, single-celled organisms that contribute to chemical cycles in the world’s oceans. Common Rhizaria (e.g. Acantharea, Foraminifera, Polycystines, Phaeodarea) form mineral shells that are part of the ocean’s strontium, silica, and carbon budgets, and they represent at least 5.2% of the oceanic biological carbon reservoir in the surface zone. Better understanding of groups of Rhizaria that are present, their biomass, and how their populations change across different ocean depths is essential to model oceanic nutrient cycles, but this information is poorly resolved or lacking for large Rhizaria in one of the largest biomes on Earth, the central, low-nutrient ocean gyres. This collaborative project involves a team of early career and more established investigators, provides measurements needed to develop a model of Rhizaria contribution to sinking nutrients in the deep ocean, and is adding to our understanding of how nutrients move in the oceans and how changing environmental conditions affect those cycles. It is generating large datasets that can be used by oceanographic researchers and is delivering oceanographic, biological, and data-science themed experiential learning opportunities for undergraduate, graduate, and high school students.This study provides 1) greatly improved estimates of total Rhizaria biomass in the oligotrophic ocean, 2) novel measurements of vertical distribution and environmental niche characteristics of Rhizaria, 3) measurements of seasonal variation in Rhizaria biomass and community composition, 4) identification of the environmental drivers of seasonal and spatial variation in Rhizaria populations, and 5) a model-based estimate of the contributions of Rhizaria to vertical flux into the deep ocean. The investigators are using a combination of Niskin bottle sampling, particle gel traps, net tows, and cutting-edge in situ imaging (using an Underwater Vision Profiler, UVP5-DEEP) of Rhizaria to bypass limitations in other sampling methods to produce accurate estimates of Rhizaria biomass. Sampling occurs across a wide depth range (0-1200 m), at monthly intervals, and in conjunction with a wide array of other oceanographic measurements collected as part of the Bermuda Atlantic Time-series Study (BATS). UVP imagery data is integrated with molecular identification of Rhizaria using community metabarcoding, ZooSCAN imaging, and barcoding of individual Rhizaria collected from net tows and gel traps taken in conjunction with UVP casts. The investigators are using size-specific elemental analyses of Rhizaria and seasonally and vertically explicit estimates of Rhizaria biomass to model Rhizaria contributions to vertical flux. Along with data collected by the Bermuda Atlantic Time Series and Ocean Flux Program, new data on Rhizaria are being incorporated into a model of carbon and nutrient transfer into the deep ocean. The model estimates three ways that Rhizaria likely impact the carbon cycle -- by feeding on particle flux, by contributing ballast to marine snow, and by sinking directly -- and shows how these might vary across space and time. This project is jointly funded by the Biological Oceanography, Chemical Oceanography, and Established Program to Stimulate Competitive Research (EPSCoR) Programs.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.