Ecology and Evolution of Arctic Marine Microbial Communities

北冰洋的决定性特征是薄薄的一层海冰，几千万年来，冰层或多或少地连续覆盖着北冰洋表面。北极海水和海冰中的海洋微生物(包括细菌、古生菌、真菌、原生生物、藻类和病毒)有数百万年的时间来适应那里的极端条件，包括常年零度以下的温度、高盐水盐度和长时间的黑暗和日光。然而，在过去的40年里，冰盖已经开始融化。北极海冰的面积和数量都急剧下降，导致人们对现在季节性不结冰的水域的航运、勘探和资源开采的兴趣增加。虽然北冰洋的变化比地球上任何其他环境都快，但我们的观测工作并没有跟上。然而，高通量DNA测序的最新进展使在时间和空间尺度上观察微生物群落成为可能，而这在上一代人之前是不可想象的。我的探索计划的长期目标是利用新的测序技术，从生态系统服务的角度为北极海洋微生物群落的生态和进化模型做出贡献，促进我们对过去、现在和未来气候变化对这些天气良好的生态系统的影响的理解。这项为期5年的发现计划的具体目标是(1)确定微生物种群功能适应的基因组指标，以及(2)对海冰和海水中微生物群落在多个时间尺度上的演替提供新的见解。目标(1)通过极大地增加北极海洋微生物环境中可获得的完整基因组的数量，将导致北极海洋微生物进化模型的改进。使用长读纳米孔测序技术将能够组装许多封闭的、循环的冷适应细菌和古生菌基因组，这些基因组将被用来通过比较基因组学评估功能和冷适应的进化模型，并深入了解水平基因转移所起的作用。目标(2)将通过极大地提高观察群落演替的时间分辨率来改进北极海洋生态系统的生态模型，这通常是由于后勤困难而稀少的。然而，我将利用位于哈德逊湾的一个新的北极研究设施--丘吉尔海洋天文台(CMO)。该设施将提供全年获取冷海水的途径，使高时间分辨率的海水微生物演替模型能够响应温度、盐度、光照、营养物质和冰的动态。同样，我将在CMO(10m X 10m X 3m)的大型中温槽中获取海冰，用于分析冰冻和融化动态导致的微生物群落结构的快速变化，这些变化已经因气候变暖而发生了实质性变化。

The defining characteristic of the Arctic Ocean is the thin layer of sea ice that has covered its surface more or less continuously for tens of millions of years. Marine microbes in Arctic seawater and sea ice (including bacteria, archaea, fungi, protists, algae, and viruses) have had millions of years to adapt to the extreme conditions there, including perennially subzero temperatures, high brine salinity, and long periods of extended darkness and daylight. However, in the last 40 years, that ice cover has started to melt. Arctic sea ice extent and volume have both declined precipitously, resulting in increased interests in shipping, exploration, and resource extraction in the now seasonally ice-free waters. While the Arctic Ocean is changing faster than any other environment on Earth, our observational efforts have not kept up. However, recent advances in high-throughput DNA sequencing have allowed the possibility of observing microbial communities at temporal and spatial scales that were unimaginable only a generation ago. The long term goal of my Discovery program is to take advantage of novel sequencing technologies to contribute to ecological and evolutionary models of Arctic marine microbial communities from an Ecosystem Services perspective, advancing our understanding of the effects of past, current and future climatic changes on these bellweather ecosystems. The specific Objectives of this 5-year Discovery proposal are (1) to identify genomic indicators of functional adaptation in microbial populations, and (2) to provide novel insights into microbial community succession in sea ice and seawater over numerous time scales. Objective (1) will lead to improvements in evolutionary models of Arctic marine microbes by greatly increasing the number of complete genomes available from these environments. Using long-read nanopore sequencing technology will enable the assembly of many closed, circular genomes for cold-adapted bacteria and archaea, which will be used to assess evolutionary models of functional and cold adaptation through comparative genomics, and insights into the role that horizontal gene transfer plays. Objective (2) will lead to improvements in ecological models of Arctic marine ecosystems by greatly increasing the temporal resolution by which community succession can be observed, which is typically sparse due to logistical difficulties. However, I will make use of a new Arctic research facility located on Hudson Bay, the Churchill Marine Observatory (CMO). This facility will provide year-round access to cold seawater, enabling high-temporal-resolution models of seawater microbial succession in response to temperature, salinity, light, nutrients, and ice dynamics. Likewise, I will obtain sea ice grown in large mesocosm tanks at CMO (10m x 10m x 3m) for analysis of rapid changes in microbial community structure resulting from freezing and melting dynamics, which have already been substantially altered by climate warming.