So, first things first. The McMurdo dry valleys SUCK to live in. They are cold, dry, lack shade, lack food, and are overall a hard place to not die.
|Much like a blender in this regard.|
Yet these valleys are full of organisms that are very distinctly not dead.
These not dead fungi are the subject of our research. Specifically, we are studying how long they can survive being completely dried out. Why? Well we've talked in the past about the potential usefulness of desiccation resistance in bioengineering and providing evidence for lithopanspermia (CLICK HERE). Those fields of study, while interesting, are not what we are focusing on. Our focus is to look at...
|The working title of our paper.|
|Summarized quite nicely here by Spongebob.|
However, the piece that is often overlooked is that the opposite is true too. Organisms that are adapted for a harsh environment often have a lot of difficulty surviving in a not harsh environment. This is why you don't see cacti growing in the middle of fields. The parts of them that allow them to go for a long time without water use up a lot of energy and cause them to grow slowly. Grass, which grows quickly but can be killed fairly easily, quickly soaks up all the resources and leaves none for the cactus, causing it to starve. This process of organisms fighting over resources is called Competition.
|Those poor cacti.|
The Dry Valleys are dry, but not uniformly so. Some areas are outrageously dry and have almost no water, other areas can be surprisingly moist for large portions of the year.
We were curious to see how available water effected where organisms could be found. If we found that organisms that are very tolerant to drying out live in only dry areas, while organisms that are not tolerant to drying out live in not dry areas, we can conclude that the level of water strongly effects where these organisms decide to live. In our experiment we dried out fungi from different parts of the dry valleys and then checked how many survived. Here is an abbreviated version of what we found.
This graph shows how many individuals survived after spending various amounts of time dried out. Some organisms did just fine and had almost no deaths (the green line). Other organisms had a lot of deaths at the very beginning of the experiment, but had their death rate slow down as the experiment went on (orange line). The blue line on this graph represents an organism that is not found in the Antarctic and should have absolutely no tolerance for desiccation. As expected, this organism died off almost immediately.
So, the data above shows that some organisms survive drying out better than others. By doing a bit of research we found that the organisms that survived desiccation are the same ones that are often found in the very dry areas of the Dry Valleys. However, we also found that these organisms were not restricted to these areas, meaning we could find them in areas that were very dry, and in some areas that were very wet.
So what does all this mean? Well, we know that all the fungi in the Dry Valleys (or at least the fungi we tested) have at least some desiccation tolerance. We know this because all the Antarctic fungus survived longer than a species that was not from the Antarctic. Next, we know that desiccation partially, but not completely, controls where an organism can live. Organisms with less tolerance can't survive as well in dry areas, but organisms that do withstand a lack of water do just fine in wet areas. Since we now know that desiccation does not completely control where an organism lives, we know that other factors must also have some control on them. These factors are probably the other stresses like cold, and high UV radiation, and food availability.
Whew, that was a bit thick. Thanks for reading!
By Ben Segee