Arctic Winter Sea Ice: A Biological Museum or Evolutionary Playground? - Jody Deming

NABT 2009. During winter, the sea ice cover in the high Arctic grows and thickens, entrapping small organisms into its interior pore spaces. As temperatures drop, these spaces shrink in size as more pure water freezes, leaving behind high concentrations of sea salts that depress the freezing point and keep the sea-ice pores filled with liquid. Only single-celled microorganisms remain in this micrometer scale subzero salty habitat. There they are free of all grazers -- except viruses. Under conditions of environmental stress, viruses often fail to kill their hosts upon infection, instead incorporating as new DNA into their hosts' genomes. In the process, they can bring new genes from former hosts into the DNA of their new hosts. This striking form of horizontal gene transfer can be an adaptive boon for the microbes. The thick sea ice in the darkness of Arctic winter that has long appeared to Arctic explorers as a frozen museum for any life entrapped within it may in fact be an evolutionary playground where microbes and viruses interact in positive ways to bring new adaptations into the realm of oceanic microbes. Given the astronomical numbers of microbes that are trapped in the polar ice cap each year, returning to the ocean when the ice melts in summer, this form of evolution may contribute substantial

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Science & Technology

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• Evolution
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