The Microbial Carbon Pump and Bacterial Carbon Sequestration in the Ocean

长期以来，生物泵一直被认为是大气中二氧化碳浓度的重要汇，因为它固定了海洋沉积物中的碳。细菌对海洋难溶有机碳(RDoC)库中碳的固存作用直到最近才被认识到。这一过程被概念化为微生物碳泵(MCP)，在碳固存和大气二氧化碳调节方面似乎也发挥着重要作用。在这个项目中，南卡罗来纳大学哥伦比亚分校的研究人员将以MCP的框架为基础，解决以下假设：1)细菌DOC的产生和组成随海洋中的生物(例如群落结构)和物理化学(例如营养物质)参数而变化，2)细菌在半不稳定DOC(SDOC)中固存碳，在中上层水域持续数年至数十年，3)中深海和半深海水域的微生物群落具有产生和降解细菌DOC的代谢潜力。自然产生的细菌DOC对微生物的降解具有很强的抵抗力，4)异养细菌是细菌SDOC和RDOC的主要来源。这些假说将使用现场(西北太平洋和马尾藻海)和实验相结合的方法来解决，以研究细菌DOC产生和分解的空间变异性，并将这些过程与群落结构和环境条件联系起来。这项研究将提供对海洋中细菌SDOC和RDoC储量的估计，以及关于海洋碳循环和大气二氧化碳浓度调节的关键见解。它还将为解决MCP和细菌固碳将如何应对气候变化奠定基础。更广泛的影响：该项目将加强国际和平研究所的实验室与小川博士在日本大气和海洋研究所的实验室之间的合作。这项合作包括参加由日本赞助的搭乘R/V Hakuro Maru前往北太平洋的探险活动。此外，它还将支持一名博士后助理和一名博士生参加西北太平洋和马尾藻海的研究考察。他们的研究将集中在MCP上，他们将在第二年和第三年的全国会议上公布他们的发现。

The Biological Pump has long been recognized as an important sink for atmospheric CO2 concentrations through the sequestration of carbon in ocean sediments. The contributions of bacteria to the sequestration of carbon in the ocean reservoir of refractory dissolved organic carbon (RDOC) have only recently been recognized. This process, conceptualized as the Microbial Carbon Pump (MCP), also appears to play a significant role in carbon sequestration and the regulation of atmospheric CO2. In this project, researchers at the University of South Carolina at Columbia will build upon the framework of the MCP to address the following hypotheses: 1) The production and composition of bacterial DOC vary with biological (e.g. community structure) and physicochemical (e.g. nutrients) parameters in the ocean, 2) Bacteria sequester carbon in semi-labile DOC (SDOC) that persists for years to decades in mesopelagic waters, 3) Microbial communities in mesopelagic and bathypelagic waters have the metabolic potential to produce and degrade bacterial DOC. Naturally-occurring bacterial DOC in these waters is very resistant to microbial degradation, 4) Heterotrophic bacteria are the predominant source of bacterial SDOC and RDOC. These hypotheses will be addressed using a combination of field (NW Pacific Ocean and Sargasso Sea) and experimental approaches to investigate spatial variability in the production and decomposition of bacterial DOC and to relate these processes to community structure and environmental conditions. This study will provide estimates of the reservoirs of bacterial SDOC and RDOC in the ocean and critical insights about the ocean carbon cycle and the regulation of atmospheric CO2 concentrations. It will also lay a foundation for addressing how the MCP and bacterial carbon sequestration will respond to climate change. Broader Impacts: This project will strengthen collaborations between the PI's laboratory and Dr. Hiroshi Ogawa's laboratory at the Atmosphere and Ocean Research Institute in Japan. This collaboration includes participation on a Japanese-sponsored expedition to the North Pacific Ocean aboard the R/V Hakuro maru. Additionally, it will support a postdoctoral associate and a doctoral student who will participate on research expeditions to the NW Pacific Ocean and Sargasso Sea. Their research will focus on the MCP, and they will present their findings at national conferences in years 2 and 3.