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

世界上一半的湖泊定期冻结，但冻结的持续时间每年都在缩短。这种模式将在地方和全球层面产生巨大影响。虽然已知冰的存在、冰的持续时间的变化以及冰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，但关于湖冰如何影响北部淡水的生物地球化学和生态的信息却很少。大多数北方湖泊都很浅，大部分的水量在冬季结冰，同时捕获化合物、气体和生物，并提供维持生物生产的冰-水界面。该项目将解决与加拿大北极湖冰相关的碳、营养和浮游生物食物网的新兴和迫切需求。该研究计划作为培养两名博士和两名硕士研究生的项目，他们将在水生科学方面拥有广泛的技能。研究将在努纳武特的剑桥湾周围进行，在那里20公里半径内发现了100个大小和深度不同的湖泊。该项目将解决首要问题：北方淡水生态系统如何应对冰的冻结、存在和融化。冬季冰盖连接了两个开放的水域季节，因此另一个关键问题出现了：在冬季期间，冰中的物质和气体是否会持续积累和产生，还是会有突然的变化，例如在极地冬季之后太阳辐射会增加？考虑到这些水位于包含永久冻土的集水区，人们对这个问题特别感兴趣：湖冰将如何与从融化的永久冻土中释放出的越来越多的有机和无机颗粒发生反应？因此，该项目将解决这样一个问题：这些颗粒的含量是被困在冰中并转移到生物生产中，还是转化为温室气体？通过表征有机和无机碳和营养体系，以及藻类及其在每个湖泊的冰和水之间的分配，以及浮游生物消费者对它们的消耗，这项研究将产生北极淡水生态系统的新视野，这是第一次解释冬季冰盖对北极湖泊功能的影响。它将与北极圈北部正在进行的多次永久冻土和湖泊研究联系起来，并提供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.