Notes from a Defense (cross-posted from S.A.G.A.N.)

I wrote this while my friend and colleague Marcela Ewert presented her work at her Ph.D. defense. She’s been doing a lot of really cool work about how Arctic microbes make their living despite the temperature and salinity extremes found in the sea ice and in the snow that rests on it. Here’s a link to some of the work included in her dissertation.

Jargon note: exopolysaccharides, also known as extracellular polysaccharides or EPS, are substances secreted by microbes (bacteria, algae, etc.) You may be familiar with extracellular polysaccharides like xanthan gum, which is produced by a soil bacterium and used as a thickener by the food industry. The exopolysaccharide produced by the Arctic microbes Marcela studies seems to be especially good at sticking to ice.

Colwellia and Psychrobacter are both species of sea-ice-dwelling bacteria.

Bacteria in Arctic Sea Ice and Salty Snow

Our universe is full of water ice
Whose particles in stellar-forming clouds
Are substrates on which molecules can splice
To veil the ice in thin organic shrouds.
On Earth, the ice on mountains and near poles
Plus snow and sea ice makes the cryosphere
In cold ecologies it plays its roles;
Sea ice and salty snow concern us here.

As sea ice forms, its icy fingers reach
Encapsulating nets of salty brine
And with the salty water, many creat-
ures will be trapped–by chance, or by design?
Bacteria and algae both secrete
Ice-loving exopolysaccharide
Which grips the icy matrix to defeat
The brine flow that would carry them outside
But in snow, changing temperatures and salt
To microbes like Colwellia spell doom
While Psychrobacter lives through this assault
And finds home where Colwellia finds a tomb.

But with the proper solutes all can thrive
And Arctic ice and snow can come alive.

157 degrees of latitude in 63 days

So I’m about to leave again for another session of fieldwork and I haven’t even finished posting the updates from the last one. Embarrassing.

Anyway, on Monday I’ll be leaving for Longyearbyen, in Svalbard, an archipelago and territory of Norway at around 78 degrees North. I’m assisting my colleague Bonnie with some measurements of the optical properties of sea ice in the fjords near there–somewhat similar stuff to what I was doing in Antarctica, although not for the same project (the sea ice we’ll be dealing with there is much warmer and more full of algae than anything we’d expect to find on Snowball Earth, at least based on current models.)

I’m pretty excited about this! The Arctic is very different to the Antarctic, in a lot of ways, and despite growing up in Alaska this will be the first time I’ve been north of the Arctic Circle. While the Antarctic is ice-covered land surrounded by water, the Arctic is ice-covered water surrounded by land, so it’s much less isolated. Land ice and sea ice are very different physically, as well, with land-based glacier ice being quite stiff and slow and clean and orderly compared to chaotic, ridged, constantly-shifting, salty, life-harboring sea ice.
The Antarctic has no land-based predators larger than a tiny worm, whereas in the Arctic we’ll have to keep an eye out for polar bears, a species that has few compunctions about eating humans if given the chance. (I’m told that if we’re on our guard and prepared, we’ve little to worry about.)

I’ll post again when I get there.