Microbial Oceanography Links to New aerosols in Ice-covered Regions (MjOLNIR) in the Arctic Ocean

今天地球上最剧烈的环境变化发生在北冰洋。最近的模型预测，北极夏季海冰可能会在世纪上半叶完全消失。夏季浮冰面积的迅速减少将导致海冰群落和北冰洋开放沃茨内微生物群落结构和生产的变化。随着夏季海冰微生物群落被开放的海洋种群所取代，确定释放到大气中的化学化合物（如各种气溶胶）的变化可能在确定未来海冰减少的速度和影响方面发挥重要作用。微生物产生的气溶胶最终将穿过海洋到达空气边界，并可能影响云的形成，并对影响北极系统的反馈产生影响。 在这项研究中，研究人员将使用最先进的方法来测量与海冰，融化池，海冰引线和公海中发现的微生物群落相关的气溶胶的相对丰度。更好地了解这些微生物群落结构的变化将为下一代模型提供新的信息，并可能导致对各种气候反馈回路的更复杂的理解。此外，该项目涉及与瑞典极地研究人员的合作，并将加强美国和瑞典科学家之间的科学联系。该项目将支持对研究生和本科生的培训，研究人员将通过讲座（作为培养计划的一部分）和社交媒体与公众分享研究成果。研究人员将调查对比海冰和开放海洋北极生态系统中的原位微生物群落组成和生产力如何影响生物源性挥发性有机碳（VOC）化合物的产生和释放。这些VOC化合物有助于释放和产生最终形成云凝结核的气溶胶。此外，研究人员还将进行船上操纵实验，以确定海面温度升高、光照强度增强以及海冰融化和水柱分层增强导致的盐度降低的影响。这些变化将对微生物群落施加生理压力，这可能会影响浮游植物群落结构和生物硫痕量气体二甲基硫（DMS）的通量。研究人员将测试温度，盐度和光照如何影响微生物群落的组成，从而影响DMS前体二甲基磺基丙酸酯（DMSP）的分解代谢命运，以产生DMS或甲烷和甲烷（CH 4）。此外，研究人员将测试在北冰洋表面沃茨观察到的高甲烷浓度是由于DMSP催化剂还是甲基膦酸盐的分解。使用最先进的仪器，他们将使用船上质子转移反应质谱仪（PTR-MS），膜入口质谱仪和高速分选流式细胞仪来监测VOC通量，分别测量VOC，净群落产量和微生物群落组成。他们将使用新开发的附在PTR-MS上的碎冰机直接测量海冰中的挥发性有机化合物，以提供关于海冰群落中二甲基硫和甲烷浓度的新的原位数据。

The most dramatic environmental changes occurring on the Earth today are taking place in the Arctic Ocean. Recent models predict that complete summertime Arctic sea ice loss will likely occur in the first half of the 21st century. The rapidly-declining areal expanse of summer pack ice will lead to changes in microbial community structure and production within both sea-ice communities and in the open waters of the Arctic Ocean. As summer sea ice microbial communities are replaced by open ocean populations, identifying changes in chemical compounds, such as various aerosols, that are released to the atmosphere might play a significant role in determining the future rate and impact of sea ice decline. The aerosols produced by microorganisms will ultimately move across the sea to air boundary and could affect cloud formation and with feedbacks that impact the Arctic system. In this study, the investigators will use state-of-the art methods to measure the relative abundances of aerosols that are associated with the microbial communities found in sea ice, melt ponds, sea ice leads, and in the open ocean. Better understanding of the changes in the structure of these microbial communities will provide new information for the next generation of models and may lead to more sophisticated understanding of various climate feedback loops. In addition, the project involves a collaboration with Swedish polar researchers and will strengthen scientific linkages between scientists in the USA and Sweden. The project will support training for graduate and undergraduate students, and the investigators will share research results with the public through lectures, as part of the Cultivate Program, and social media. The investigators will investigate how in-situ microbial community composition and productivity in contrasting sea-ice and open-ocean Arctic ecosystems impact the production and release of biogenic, volatile organic carbon (VOC) compounds. These VOC compounds are instrumental in the release and production of aerosols that ultimately form cloud condensation nuclei. In addition, the investigators will perform shipboard manipulative experiments to determine the effects of elevated sea surface temperatures, enhanced light intensities, and lower salinities resulting from melting sea ice and enhanced water column stratification. These changes will impose physiological stress on microbial communities that is likely to impact both phytoplankton community structure and the flux of the biogenic sulfur trace gas dimethylsulfide (DMS). The investigators will test how temperature, salinity, and light will affect the composition of the microbial community and thereby the catabolic fate of the DMS precursor dimethylsulfoniopropionate (DMSP), to yield either DMS or methanethiol and methane (CH4). In addition, the investigators will test whether the high CH4 concentrations observed in Arctic Ocean surface waters are due to DMSP catabolism or, alternatively, the breakdown of methylphosphonate. Using state-of-the-art instrumentation, they will monitor VOC fluxes using a shipboard Proton Transfer Reaction Mass Spectrometer (PTR-MS), a Membrane Inlet Mass Spectrometer, and high speed sorting flow cytometer to measure VOCs, net community production, and microbial community composition, respectively. They will make direct measurements of VOCs within sea ice by using a newly developed ice crusher attached to the PTR-MS to provide new in-situ data on the concentrations of DMS and CH4 in sea ice communities.