Biogeochemical and ecological consequences of the freeze-melt cycle of freshwater ice

世界上有一半的湖泊定期结冰，但结冰的时间每年都在缩短。这种模式将在当地和全球层面产生巨大影响。虽然已知冰的存在、持续时间的变化和融化时间的改变会影响极地海洋生态系统中的许多重要生物活动，但关于湖泊冰如何影响北部淡水的生物地球化学和生态的信息很少。大多数北方湖泊都很浅，冬季大部分水量冻结，同时困住化合物、气体和生物体，并提供维持生物生产的冰水界面。该项目将解决对与加拿大北极湖冰相关的碳、营养物质和浮游生物食物网的了解的新出现的迫切需求。该研究计划作为培养两名博士和两名硕士学生的项目，他们将毕业时拥有广泛的水产科学技能。研究将在努纳武特的剑桥湾周围进行，在那里半径20公里的范围内发现了100个大小和深度不同的湖泊。该项目将解决最重要的问题：北方淡水生态系统如何应对冰冻、存在和融化。冬季的冰盖连接了两个开放的水域季节，因此产生了另一个关键问题：在冬季，冰中是否存在物质和气体的持续积累和生产，或者是否存在突然变化，例如在极地冬季之后太阳辐射增加的时候？考虑到这些水域位于含有永久冻土的集水区，人们对这个问题特别感兴趣：由于融化的永久冻土释放出越来越多的有机和无机颗粒，湖泊冰将如何反应？因此，该项目将解决这个问题：这些颗粒的内容是被困在冰中并转移到生物生产中，还是转化为温室气体？通过描述每个湖泊的有机和无机碳和营养状况，以及藻类及其在冰和水之间的分配，以及浮游生物消费者对它们的消耗，这项研究将对北极淡水生态系统产生新的看法，首次考虑到冬季冰盖对北极湖泊功能的影响。它将与整个环北极地区正在进行的多项永久冻土和湖泊研究联系起来，并产生将影响政策和科学的信息。

Half of the world's lakes freeze periodically, but the duration of freezing shortens each year. This pattern will have vast consequences at a local and global level. While the presence of ice, changes in its duration, and altered timing of its melt are known to affect many important biological activities in polar marine ecosystems, there is very little information regarding how lake ice influences the biogeochemistry and ecology of northern freshwaters. Most northern lakes are shallow with much of their water volume freezing in winter, concurrently trapping compounds, gases and organisms and providing an ice-water interface that sustains biological production. This project will address the emerging and pressing need for an understanding of carbon, nutrients and plankton food webs associated with lake ice in Arctic Canada. The research program has been planned as projects for the training of two PhD and two MSc students, who will graduate with broad skills in the aquatic sciences. Research will be carried out around Cambridge Bay, Nunavut, where >100 lakes of different size and depth are found within a 20-km radius. The project will address the overarching question: how do northern freshwater ecosystems respond to the freezing, presence, and melting of ice. Winter ice cover links two open water seasons, and thus another key question arises: is there a constant accumulation and production of material and gases in the ice during winter, or are there abrupt changes, for example when solar radiation increases after the polar winter? Given that these waters lie in catchments containing permafrost, there is a particular interest in the question: how will lake ice react with the increasing amount of organic and inorganic particles released from thawing permafrost? The project will therefore address the question: is the content of these particles trapped and transferred in the ice and made available to biological production, or is it transformed into greenhouse gases? By characterizing the organic and inorganic carbon and nutrient regimes, as well as algae and their partitioning between ice and water at each lake, and their consumption by planktonic consumers, this research will generate a new vision of Arctic freshwater ecosystems, which for the first times accounts for the effect of winter ice cover for the functioning of Arctic lakes. It will link with the multiple permafrost and lake studies taking place throughout the circumpolar North and produce information that will affect both policy and science.