Ecology and Evolution of Arctic Marine Microbial Communities

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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.