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

丝核菌是一种大型的单细胞生物，对世界海洋中的化学循环做出了贡献。普通根霉(如棘藻区、有孔虫属、多胞藻属、褐藻区)形成矿物外壳，是海洋锶、二氧化硅和碳收支的一部分，它们至少占表层海洋生物碳库的5.2%。更好地了解根霉的存在、它们的生物量以及它们的种群如何在不同的海洋深度变化对于建立海洋营养循环模型至关重要，但对于地球上最大的生物群之一的大型根霉来说，这些信息没有得到很好的解析或缺乏，这一生物群是地球上最大的生物群之一，即中央低营养海洋环流。这个合作项目涉及一个由早期职业生涯和更成熟的研究人员组成的团队，提供了开发丝核菌对深海营养物质下沉的贡献模型所需的测量数据，并加深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循环的理解。它正在产生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经验学习机会。这项研究提供了1)极大地改进了对少营养海洋中根霉总生物量的估计，2)根霉垂直分布和环境生态位特征的新测量，3)根霉生物量和群落组成的季节变化的测量，4)根霉种群季节和空间变化的环境驱动因素的识别，以及5)基于模型的根霉对进入深海的垂直通量的贡献的估计。研究人员结合使用尼斯金瓶采样、颗粒凝胶陷阱、网状拖网和尖端原位成像(使用水下视觉剖面仪，UVP5-Depth)来绕过其他采样方法的限制，对根霉的生物量做出准确的估计。采样的深度范围很广(0-1200米)，每隔一个月进行一次，并与作为百慕大大西洋时间序列研究(BATS)一部分收集的一系列其他海洋学测量相结合。UVP图像数据与根霉的分子鉴定相结合，使用群落MetabarCoding、ZooSCAN成像以及从与UVP铸模相结合的网状拖网和凝胶陷阱收集的单个根霉的条形码。研究人员正在使用根霉特定大小的元素分析，以及对根霉生物量的季节性和垂直显式估计，以模拟根霉对垂直通量的贡献。随着百慕大大西洋时间序列和海洋通量计划收集的数据，有关丝核菌的新数据正在被纳入到深海碳和营养转移的模型中。该模型估计了根霉可能影响碳循环的三种方式--通过摄取颗粒通量，通过为海洋雪提供压舱物，以及通过直接下沉--并展示了这些方式可能如何在空间和时间上发生变化。该项目由生物海洋学、化学海洋学和已建立的激励竞争研究计划(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。

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.