I think most of us are aware of the news that the rapid melting of the ice shelf is unstoppable. After hearing that the ice shelf consists of snow deposits that accumulated over the last tens of thousands of years, my very first thought was this.
Will melting of this ancient ice reintroduce our world to a bacteria that our world isn’t as familiar with as it was many millennia ago? Sure, I believe that we’re still coming out of an ice age, and that to some extent this melting is a natural part of the planet’s story, but we’re definitely helping to hurry things up. With the fluctuation of the ice sheets (you know, growing during ice ages and shrinking on the other end of the cycle), there’s probably a wide variety of history in that ice, especially in its biological makeup.
So, what’s trapped in that ice? If snowflakes take their shape from the bacteria that the water molecules form around, we know that snow has bacteria at its core. Bacteria is everywhere. Imagine what kinds of bacteria flourished tens of thousands of years ago. What would happen when this snow, or ice, melts?
Can bacteria survive freezing temperatures?
Of course they can. Extremophiles that thrive in the cold are everywhere, especially in bacterial form. Thermophiles thrive at high temperatures and psychrophiles thrive at very low temperatures. According to Wikipedia, “Psychrophiles are extremophilic organisms that are capable of growth and reproduction in cold temperatures.”1 Although it helps for bacteria to be cold-hearty, it doesn’t have to be an extremophile to survive in ice. Yes, some bacteria will be killed off, but that just means that the hardiest of the bunch will survive a big freeze.
According to the Microsoft Encarta Reference Library:
“Extremophiles are organisms that can grow in conditions considered harsh by humans. Some kinds of bacteria thrive in hydrothermal vents on the ocean floor or in oil reservoirs within Earth, at high pressures and temperatures as high as 120ºC (250ºF). Other kinds can live at temperatures as low as –12ºC (10ºF) in Antarctic brine pools. Other bacteria have adapted to grow in extremely acid conditions, where mines drain or minerals are leached from ores and sulfuric acid is produced. Others grow at extremely alkaline or extremely salty conditions. Still others can grow in the total absence of oxygen. Bacteria able to function in these extreme conditions generally cannot function under conditions we consider normal.”
Let’s talk about temperature.
How cold does ice get in a glacier?
“The temperature of ice within a glacier changes with depth. Snow falling on the surface of a glacier is the same temperature as the air at the surface. As more snow falls, the older snow is pushed down into the glacier, taking that surface temperature with it. In polar regions, where air temperatures are very cold, ice near the surface of a glacier is also very cold. But with depth, ice temperature increases because the ice is being warmed from below by geothermal energy from Earth. Many alpine glaciers are isothermal (of a nearly uniform temperature), and are very near the melt temperature throughout.”2
Interested in reading more about glacial temperature profiles? Read this.
All of this information doesn’t seem very straightforward, but it does make me realize how varied (thermally) of an environment we’re looking at. Bacteria can emerge that was subject to gently frozen temperatures, as well as really, really extreme cold. There could be a wide variety of psychrophile bacteria emerging from glacial melting, yes? From what I’ve found, the coldest glaciers could get is around -13ºC. Psychrobacter, a genus of psychrophile bacteria, is capable of growing at temperatures between −10 °C and 42 °C. Keyword: “growing.” This means there could be bacteria alive and well in a glacier. 3
In addition, cold-hearty bacteria also has something else on its side. Endospores. “Certain genera of Gram-positive bacteria, such as Bacillus, Clostridium, Sporohalobacter, Anaerobacter, and Heliobacterium, can form highly resistant, dormant structures called endospores… Endospores show no detectable metabolism and can survive extreme physical and chemical stresses, such as high levels of UV light gamma radiation, detergents, disinfectants, heat, freezing, pressure, and desiccation.”4
I don’t know about you, but it sounds like bacteria will be fine in a glacier. Most may be hibernating, while some thriving. I would imagine those types of bacteria that could thrive in a glacier may probably be starving since their organic energy source is probably very scarce. Then, when their habitat melts they may be a little too warm to be comfortable. I think the bacteria that would thrive the most post-thaw are simply those bacterium that are hibernating in a cryogenic state.
In February of 2013 scientists found bacteria living under the antarctic ice. As the scientists studied this bacteria, John C. Priscu of Montana State University, the leader of the expedition, showed signs of concern of contamination. According to the New York Times, he “said that every precaution had been taken to prevent contamination of the lake with bacteria from the surface or the overlying ice. In addition, he said, the concentrations of life were higher in the lake than in the borehole, and there were signs of life in the lake bottom’s sediment, which would be sealed off from contamination.”5
Hmm. Yes, I’d say there is some validity in my thoughts about reintroduction of bacteria into the oceans. Here’s some knowledge from the Microsoft Encarta Reference Library.
“All organisms have some capacity to adapt to environmental stress, but the extent of this adaptive capacity varies widely. Heat, cold, high pressure, and acid or alkaline conditions can all produce stress. Bacteria easily adapt to environmental stress, usually through changes in the enzymes and other proteins they produce. These adaptations enable bacteria to grow in a variety of conditions. Gradual exposure to the stress, for example, may enable bacteria to synthesize new enzymes that allow them to continue functioning under the stressing conditions or that enhance their capacity to deal with the stressing agent. Or they may resist environmental stress in other ways. Some bacteria that live in extremely acidic conditions can pump out acid from their cell.”
So, bacteria can easily adapt to environmental stress. Bacteria was also around long before we were, and from a 30,000-foot view of life on earth they could simply see us as a messy blip on their radar. Read this.
When that ice melts, if any new, ancient bacteria re-enters the ecosystem things will change and a new balance will be reached, whether at a small or large scale. It’s not just about the rise of the sea level, even though that’s the impact that’s getting all of the attention. In my totally uneducated opinion, just about anything can happen from such a wide-reaching event.
Have you seen photos of what bacteria, specifically Alcanivorax borkumensis, does to oil slicks? Imagine some new type of bacteria thawing out and having a heyday on our ripe oceans like it did the recent oil spill in the Gulf of Mexico. It’ll be über-hearty and really hungry. Sure, some bacteria may not be able to handle the salinity or the current level of acidity in our oceans, but some will love it. I feel that I’m actually at a point now at which, if left to my own curiosity, I can easily get carried away with my thoughts.
Well, it just so happens that I’m about two years too late. Scientific American covered this in April of 2012. Our friend, John Priscu, takes center stage again.
“Once thought to be too harsh and inhospitable to support any living thing, the ice sheets are now known to be a gigantic reservoir of microbial life. Altogether, the biomass of microbial cells in and beneath the ice sheet may amount to more than 1,000 times that of all the humans on Earth.” Creepy. Only time will tell, eh?