Collaborative Research: Transforming Carbon in the Deep Sea

通过了解生物泵（海洋生物驱动的碳从大气到海洋内部和海底沉积物的封存），科学家们知道，世界上的海洋吸收的二氧化碳比它返回到大气中的二氧化碳要多。虽然对主要负责将碳转移到深海的生物过程了解很多，但对碳到达深海时发生的微生物腐烂和随后的再矿化过程知之甚少。利用部署在美国东海岸的新设计的深海孵化器，研究人员将探索深海中转化碳的微生物群落和再矿化过程。孵化箱将充满示踪剂标记的藻类或粪便材料，模仿浮游动物的饮食和废物。示踪剂使研究人员能够通过微生物食物网跟踪材料，同时确定孵化过程中二氧化碳的净释放量。利用遗传分析和新型分析技术的结合，研究人员将能够识别参与衰变过程的生物体，以及单细胞水平上发生变化的速率。结果将揭示这些未被充分研究的生物现象，并有助于提高对全球碳循环的理解。除了在海洋学技术方面取得新进展外，该研究还支持研究生和本科生的教育，并通过与弗吉尼亚水族馆和国家海洋科学碗的合作伙伴关系进行公众宣传，以提高海洋科学素养。在本项目中，研究人员将研究深海有机物质再矿化的生物、机制以及调节有机物质再矿化的物理和生态因素。方法包括将定义明确且稳定的同位素标记的有机碳源（活的和死的浮游植物以及浮游动物的粪便颗粒）与天然微生物群落进行原位孵育。孵化将在哈特拉斯角东北部进行，该地区的特点是浮游植物碳的海上运输很强。随着时间的推移，二氧化碳的净释放率将通过碳-13标记的有机碳转化为13CO2来测量。将评估降解率对源材料、季节性、氧浓度和微生物定植菌类型的依赖。平行实验室实验将阐明浮游植物向溶解的有机和无机组分释放碳的时间过程的确切形状，并确定具有代表性的实验室和船上产生的值与原位获得的值相比如何。培养后通过荧光原位杂交（FISH）鉴定目标真核生物和原核生物分类群，并使用拉曼显微光谱法单独调查同化标记碎屑碳的生物中碳-13的相对富集率。这种多方面的方法将为生态系统和生物泵模型提供更好的约束参数，并阐明深海的碳平衡。该研究有助于开发新的海洋技术，包括新的深海培养箱和单细胞拉曼显微光谱法在天然微生物群落中的应用。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。

Through understanding the biological pump (the ocean's biologically driven sequestration of carbon from the atmosphere to the ocean interior and seafloor sediments), scientists know that the world's oceans absorb more carbon dioxide than it returns to the atmosphere. While much is known about the biological processes largely responsible for the transfer of carbon into the deep sea, very little is known about the microbial decay and subsequent remineralization processes that occur when the carbon reaches the deep sea. Using newly-designed deep-sea incubators deployed off the east coast of the United States, researchers will explore the microbial communities and remineralization processes that transform carbon in the deep sea. The incubators will be filled with tracer-labeled algae or fecal material mimicking the diet and waste products of animal plankton. The tracers allow the researchers to follow the material through the microbial food web, and simultaneously determine the net release of carbon dioxide during the incubations. Using a combination of genetic analysis and novel analytical techniques, the researchers will be able to identify the organisms involved in the decay processes and rates at which changes occur at the single-cell level. Results will shed light on these understudied biological phenomena and contribute to an improved understanding of the global carbon cycle. In addition to novel advancements in oceanographic technology, the research supports graduate and undergraduate student education, and public outreach through partnerships with the Virginia Aquarium and National Ocean Sciences Bowl to increase ocean science literacy. In this project, researchers will study the organisms, mechanisms, and physical and ecological factors that modulate the remineralization of organic material in the deep sea. The methods include using in situ incubations of well-defined and stable isotope-labeled sources of organic carbon (live and dead phytoplankton and fecal pellets of zooplankton) with natural microbial communities. The incubations will take place northeast of Cape Hatteras, a region characterized by strong offshore transport of phytoplankton carbon. Net carbon dioxide release rates will be measured over time by conversion of Carbon-13 labeled organic carbon to 13CO2 . The dependence of degradation rates on the source material, seasonality, oxygen concentration, and the type of microbial colonizers will be assessed. Parallel laboratory experiments will elucidate the exact shape of the time course of carbon release by phytoplankton into dissolved organic and inorganic fractions as well as determine how representative laboratory and ship-board generated values are relative to those obtained in situ. Target eukaryotic and prokaryotic taxa are identified by fluorescence in-situ hybridization (FISH) after the incubations and individually interrogated using Raman microspectrometry to investigate the relative Carbon-13-enrichment rates in organisms assimilating labeled detrital carbon. This multi-faceted approach will provide better constrained parameters for ecosystem and biological pump models and shed light on carbon balances of the deep sea. The research contributes to the development of new oceanographic technology, including new deep-sea incubators and application of single-cell Raman microspectrometry to natural microbial communities.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.