Limitierende Faktoren der marinen Methanoxidation

尽管海洋和海洋沉积物中的温室气体甲烷产量很高，但只有约2%的气体最终到达大气层。海洋中的特殊细菌使用甲烷作为碳和能量来源，因此被认为在海洋中保持纳摩尔甲烷浓度。拟议的项目旨在调查不同的化学，生物和物理因素，增强或限制微生物甲烷氧化作为海洋中甲烷的重要汇。例如，在地表沃茨中发现甲烷氧化速率通常较低，这可能是由铜和/或铁限制或甲烷氧化细菌的光抑制引起的。此外，甲烷作为细菌的底物可能会受到限制，因为风速增加会增加海面空气的气体交换。相比之下，在水交换有限的沿海盆地的底层水中测得了高甲烷氧化率。这些高氧化速率通常与周围水中较低的氧浓度和/或增加的悬浮物质含量相关。在不同的气候带（极地：斯匹次卑尔根和南极洲，亚热带：圣巴巴拉盆地，热带：墨西哥湾）结合实验室实验的实地研究计划研究的因素，提高和限制微生物甲烷氧化在海洋中。主要是利用放射性示踪剂和稳定碳同位素研究甲烷氧化过程。因此，在不同的条件下，原位甲烷氧化细菌群落的最大吸收速率将被测量。最后，将把实地和实验室研究的结果结合起来，建立一个箱形模型，可用于估计和可能预测海洋中重要的甲烷汇之一的好氧甲烷氧化。

Despite the high production of the greenhouse gas methane in ocean and ocean sediments, only ~2% of the gas finally reaches the atmosphere. Specialized bacteria in the ocean use methane as their source of carbon and energy and, hence, are thought to maintain nanomolar methane concentrations in the bulk of the ocean. The proposed project aims to investigate different chemical, biological, and physical factors that enhance or limit microbial methane oxidation as an important sink of methane in the ocean. For example, often low methane oxidation rates have been found in surface waters, which may be caused by copper and/or iron limitation or light inhibition of methane oxidizing bacteria. In addition, methane as substrate for the bacteria may be limited due to increased sea surface air gas exchange by increased wind speed. In contrast, high methane oxidation rates have been measured in bottom water of coastal basins with limited water exchange. These high oxidation rates often correlate with lower oxygen concentrations and/or increased suspended material content in the surrounding water. Field studies in different climatic zones (polar: Spitsbergen and Antarctica, subtropical: Santa Barbara Basin, tropical: Gulf of Mexico) in combination with laboratory experiments are planned to study factors enhancing and limiting microbial methane oxidation in the ocean. Mainly the process of methane oxidation will be investigated by using radioactive tracers and stable carbon isotopes. Thereby maximum uptake rates of in situ methane oxidizing bacterial communities will be measured at different conditions. Finally, the results of the field and laboratory studies will be combined to develop a box model that can be used to estimate and possibly predict aerobic methane oxidation, one of the important methane sinks in the ocean.