SIMbRICS: Sea Ice Microbiology and the Role In Cycling of Sulfur (DMS, DMSP, DMSO, MT)

随着气候变化导致地球变暖，北冰洋正在经历前所未有的变化。全球气温上升导致冰川融化和退缩的速度加快，永久冻土融化，冬季海冰面积有减少的稳定趋势。由于融化速度加快，流入北冰洋的淡水也在增加。随着海冰的消退，海冰的反射表面被吸收的黑暗海洋所取代，导致对入射阳光和热能的更大吸收，从而推高了全球气温上升的速度。然而，这幅图过于简单化，北冰洋水和海冰内发生了许多我们不完全了解的物理和生物过程，但这些过程可能会影响我们对北冰洋内变化的预测。2019年秋季，德国破冰船FS Polarstein正在进行一次独特的探险，航行到俄罗斯拉普特夫海的北冰洋海冰边缘，让海冰在船周围形成。然后，这艘船将与冰层一起漂流，靠近北极，并于2020年秋季离开格陵兰岛东海岸附近的海冰。这一机会将使科学家能够接触到新形成的“第一年”海冰以及较老的“多年”海冰，并使他们能够研究北极全年环境的方方面面和所有季节变化：大气、海冰和水柱之间的物理相互作用，以及在所有三种环境中发生的生物活动。我们现在努力收集这些信息是至关重要的，因为这将使我们能够更好地了解正在发生的过程，并使我们能够改进我们对北极在未来几十年将如何变化的模型预测。该项目被设计为这次探险的关键部分，将研究一种名为二甲基硫化物(DMS)的气体的形成，二甲基硫化物是混合气体中的一种关键成分，构成了“海洋的气味”。它在世界各地都是由淡水和咸水环境中的单细胞藻类和细菌产生的，但我们之前的研究表明，海冰藻类产生的DMS浓度比水中高出数十到数百倍。虽然只有一小部分(高达16%)的DMS被释放到大气中，但一旦进入大气，它就会形成播云化合物，从而影响我们的天气和气候。当下雨时，硫化物被重新沉积到我们大陆的土壤中。海洋中形成的DMS的其余部分留在那里，面临海洋微生物的消耗和并入海洋的硫循环。众所周知，海冰是DMS的重要来源，随着气候变化的加剧，海冰面积的减少将对DMS进入大气的量产生重大影响。我们的项目旨在调查北极季节变化中微生物(细菌和藻类)群落的变化，并看看这些变化如何影响DMS和相关有机硫化合物的生产率。为此，我们将在北方春季在FS Polarstein驻扎2个月，并形成国际合作，将我们的样品供应延长到从春季到夏季的6个月以上。我们将在家庭实验室中继续我们的研究，研究我们将在海上(或在冰中)收集的所谓“模型微生物”。我们在北极收集的所有数据都将与我们之前在南极的研究进行比较，以便更清楚地了解极地地区作为DMS来源的重要性，以及随着这些地区的变化，气候变化将如何影响我们的全球气候。

The Arctic Ocean is undergoing unprecedented changes as the Earth warms due to climate change. Increasing global temperatures are resulting in increased rates of glacial melting and retreat, thawing of the permafrost and a steady trend towards reduced sea ice extent in winter. Inputs of freshwater into the Arctic Ocean are also increasing as a result of the increased melting rates. As the sea ice retreats, the reflective surface of the ice is replaced by absorptive 'dark' ocean, and results in a greater absorption of incoming sunlight and heat energy, thus driving up the rate of global temperature increase. However, this picture is too simplistic, and there are many physical and biological processes taking place within the Arctic Ocean water and sea ice which we do not fully understand, but which could affect our projections of changes within the Arctic Ocean. In Autumn 2019, the German Icebreaker FS Polarstern is undertaking a unique expedition, to sail to the edge of the Arctic sea ice in the Russian Laptev Sea, and allow the sea ice to form around the ship. The ship will then drift with the ice pack, close to the North Pole, and exit the sea ice in Autumn 2020 near the east coast of Greenland. This opportunity will allow scientists access to newly formed 'first year' sea ice, as well as older 'multi-year' ice, and allow them to study all aspects of the Arctic environment across an entire year and all the seasonal changes: physical interactions between atmosphere, sea ice and water column, and the biological activities taking place in all three environments. It is essential we work towards gathering this information now, as it will allow us much better understanding of the processes taking place, and allow us to improve our model predictions of how the Arctic will change over the coming decades. This project has been designed as a key part of this expedition, and will study the formation of a gas called dimethylsulfide (DMS), a key ingredient in the cocktail of gases that makes up the 'smell of the sea'. It is produced worldwide by single celled algae and bacteria in both freshwater and saltwater environments, but our previous research has shown that sea-ice-dwelling algae produce concentrations of DMS tens to hundreds of times higher than in the water. While only a small proportion (up to 16%) of this DMS is released into the atmosphere, once there it forms cloud-seeding compounds which can influence our weather and climate. When it rains, sulfur compounds are deposited back into the soils of our continents. The remainder of the DMS formed in the oceans stays there, facing consumption by marine microbes and incorporation into the oceanic sulfur cycle. As we know that sea ice is an important source of DMS, the reduction in sea-ice extent with increasing climate change will have significant effects on the volume of DMS entering the atmosphere. Our project aims to investigate the changes in the microbial (bacterial and algal) community across the seasonal changes in the Arctic, and to look at how these changes affect the production rates of DMS and associated organic sulfur compounds. To this end, we will undertake 2 months stationed on FS Polarstern during the boreal spring, and form international collaborations to extend our sample availability to over 6 months through spring to summer. We will continue our research in the home laboratory by studying so-called 'model micro-organisms' which we will collect during our time at sea (or in the ice!). All our data collected in the Arctic will be compared to our previous studies in the Antarctic, to give a much clearer picture of the importance of the polar regions as a source of DMS, and how climate change will affect our global climate as these areas change.