Melting glaciers in Antarctica and Greenland hold ancient microbes that will be released back into our environment as the ice sheets melt. Some of these bacteria and other microbes predate human existence; some have been trapped there since the last major climate change in earth history 750, 000 years ago known as the Middle Pleistocene period. Given that we’ve seen 420,000 year old bacteria from Antarctica come back to life – actually grow in laboratories after being taken out of the ice - there is more than a little bit to be concerned about.
The biggest concern about these microbes returning to life is that global warming is melting ice sheets at an alarming, unprecedented rate and dumping water en masse into the sea. This could potentially result in nutrients triggering growth bursts of bacteria that use up all the oxygen in the water. This would destroy aquatic habitats and expand the dead zones already occurring in the ocean.
Another concern is that viruses found in the ice could be introduced to a population that has never been exposed to it and thus has no antibodies. Scott Rogers evolutionary biologists at Bowling Green University in Ohio has discovered a plant virus in Greenland’s ice that is 140,000 years old. Should we be alarmed? Thankfully viruses have a great deal of trouble surviving in freezing environments, and scientists have no fear of a pandemic arising from their discoveries. ”The chances aren’t zero,” said Rogers, “but they’re very close to zero.”
As usual, the biggest losers will be wildlife. Associate research professor at Montana State Christine Foreman said, ”We have always thought about the ocean as being this sink that can handle everything, but we know now that’s not true.”
Once thought to be too inhospitable to support life, scientists now estimate microbial cells on the ice sheet could equal 1,000 times that of human life on the planet. Containing the oldest ice on earth, pockets of Antarctica are thought be up to 8 million years old. John Priscu, a professore at Montana State University and pioneer in the study of Antarctic microbiology, compares it to a kind of genome deep freeze. Anything on the ice is preserved until the sheet melts. Priscu’s team dated their “bugs in the ice” back 420,000 years, but other researchers claim they’ve done the same with even older deep-freeze bacteria.
These microscopic organisms bide their time, just waiting to come back to life in more favorable conditions. Scientists are at a loss to explain how. Microbiologist Brent Christner at Louisiana State University marvels that these microbes can ”sit for 750,000 years in some state of suspended animation like when Han Solo was put in carbonite.” Inside glaciers they remain in a minimally active state, preserving their DNA, and repairing any damage from oxidation or radiation. The older the ice, the longer it takes for the microorganism to revive, but some researchers believe they could in fact survive frozen indefinitely. Furthermore the microbes are evolving while frozen. They are exchanging DNA and gaining new traits. Melting glaciers aren’t just releasing ancient microbes, but improved and unpredictable ones.