Microbial Life in Svalbard

AMASE team 2010

It is generally presumed that if we are able to detect life on another planetary body, it will most likely be similar to our simplest forms of life--the microbes. Therefore, NASA’s concentrates on looking for microscopic signs of life. From the 2001 NRC report:

“The detection of extremely low levels of microorganisms after spacecraft sterilization involves increasing refinement of laboratory techniques designed to detect known types of terrestrial organisms.  It also requires research into the possibilities and consequences of failure to detect unknown or poorly known microorganisms that exist within Earth’s environment.  The detection of extant life on samples returned from another planet, or analyzed in situ, is a much less well-defined venture.  It requires a set of assumptions about the fundamental nature of life that might exist on another planet.”

         The NRC quote defined how we searched for “signs of life” during the 2004 AMASE trip as we sampled along the flanks and waters of Jotun Hot Springs. On the travertine terrace several tens of meters high, the water from three spring outflows had temperatures around 30°C. At each outflow, a small pool 1 to 5 cm deep supported a dense covering of microbes and algae, green in color, and often filamentous. As the effluents passed down the travertine slope, they cooled and were replaced by larger filamentous organisms and diatoms. I was drawn to study the thermophiles there and the scene brought back great memories of fieldwork in Yellowstone National Park. Now working with the Carnegie and JPL groups, we developed a completely different sampling and strategy plan.

         We took a step “backwards” so to speak and walked away to refrain from immediately collecting the obvious organisms in the springs and devised a coordinated sampling plan on the terraces adjacent to the springs hoping that they would present a greater life detection challenge. The Carnegie team of Andrew Steele, Jake Maule, Jan Toporski and Maia Schweizer were determining the microbial composition and biomass using field-based PCR and an ATP-based bioluminescence and LAL (Limulus  amebocyte lysate, an extract from the horseshoe crab) instrument manufactured by Charles River Laboratories. My task was to measure ammonium and nitrate extracted from these samples as well as to determine the absorption spectrum of microbial pigments. The JPL group, Pamela Conrad, Lonny Lane, and Rho Bhartia, were testing a UV-fluorescence prototype instrument. We argued for several hours on the outcrop before taking the first sample and making measurements. The microbiology group sampled first so as to avoid contamination that could come from our activities.  I sampled next, since my sampling was simple: a scoop of travertine adjacent to the microbiology sample. Last came the UV-fluorescence team who took their time troubleshooting their instrument along the way. They encountered numerous problems including computer screens that literally froze, telephone type cable connections that shrank in the cold and made no contact, and light contamination from sunlight.

         Nitrogen concentrations for both nitrate and ammonium in travertine samples were more than three times greater than volcanic rocks nearby. In waters downstream from the springs’ sources, ammonium concentrations were relatively high then decreased, while simultaneously nitrate concentrations increased to levels similar to those of ammonia in sources.  These data clearly indicate microbial nitrification. Pigments were extracted in the field at 4°C (ambient air temperature). In these “off axis” samples, the absorption peaked at about 400-450 nm, indicative of the Soret band of chlorophyll, the green pigment in plants. In many samples, light absorption in the near ultra-violet (UV) range (360-400 nm) indicated the presence of the pigment scytonemin, a microbial pigment synthesized to protect organisms from UV damage. The absorption bands were especially strong in what we called “black” and “white” sediments.

On the way to Troll Springs, crossing an Arctic River

         Back in the lab at the Carnegie, I analyzed total nitrogen as well as the carbon and nitrogen isotope biosignatures of the organic matter of these samples. Total nitrogen in these sediments was five times greater in hot spring sediments relative to adjacent volcanic rocks. Compared to the extractable, inorganic nitrogen measured on board ship, the total nitrogen was overwhelmingly organically bonded nitrogen. The isotope patterns of carbon and nitrogen in biomass and rock samples from Jotun Springs varied over short distances reflecting the activity of living microbes in effluent waters. If there had been no microbial activity, I would have found uniform isotope patterns.        

         Based on the carbon signatures of microbes, we surmised that the concentration of dissolved CO₂ coming from the hot spring sources must be high. Again, if we were measuring the carbon signals of abiogenically derived organic carbon, we would expect the patterns to be much more uniform. On Earth, the “background” value measured in what is supposed to be “clean” materials Is actually slight oil contamination that is ubiquitous.  I concluded that 1) based on changes in nutrient concentrations over the spatial extent near the springs, 2) elevated concentrations relative to igneous rocks, 3) the absorption of light in the visible and near UV region, and 4) the variable isotopic compositions that these represented biosignatures of life in these samples.  

         Over the years, we made many trips to Troll Springs, which are located about 6 km from the shoreline. The hike there circumnavigated Sverrefjell Volcano, crossed a marshy area where we had to step on clumps of moss to prevent sinking in quicksand, before reaching a rushing, cold Arctic river about 100 m wide. There were few comfortable or safe options for crossing the river. Option one, encase your hiking boots in trash bags and run quickly through the water, hoping the bags stayed on your boots. Option two, put the trash bags over your feet, then back in your boots. Wade more surely through the river channel, but you’ll have wet boots on the other side. Option 3, run as fast and as fleet as you can and hope that your boots remain as dry as possible. All three options generally resulted in cold feet and wet boots. Having a dry set of socks in your backpack was a good idea.

         Troll Springs spread out on the landscape for about 500 m. Some of the springs had dried completely, while others were going full blast. Those with active flow supported robust communities of microorganisms (Starke et al., 2012). Gases emitted from the springs had high concentrations of CO₂ (Jamtveit et al., 2008). I measured nutrients and pigments in soils, sediments, and springs from this area for many years. Particularly interesting were the rock samples in which the cyanobacteria and other microbes were found mainly within cracks and crevices (e.g. endoliths).

Polar bear eating a seal on an ice flow

         In 2004, we discovered a relatively small area at Troll Springs littered with hundreds of small bird bones. Upon closer inspection, we realized the bones were clustered around an Arctic fox den, which was situated on the side of a dormant spring where the soil was warmed year round. Immediately, I collected bones and soils from around the den. During repeated trips to Troll Spring over the next five years, it appeared that a fox inhabited this den continuously. Based on the isotopic composition of the soils, I found that the fox’s “influence” on the landscape through its feeding and excreting activities extended 60 m in three of the cardinal directions (e.g., North, South, East, and West) from its den. Plants growing on those soils had distinctive isotope values for both carbon and nitrogen that showed “fertilization” from prey caught on the shorelines. Isotopic analyses of the small bird bones showed the fox diet consisted of both terrestrial (e.g. ptarmigan) and marine birds. About 80% of the bones were from marine seabirds, such as kittiwakes. Accordingly, the fox was responsible for bringing nutrients from the ocean into a nutrient-starved terrestrial environment creating a green, “hot spot” that could be seen from some distance. Although “foxes on Mars” is a ridiculous notion in itself, this discovery was a robust example of how biological processes of organisms can physically and chemically alter the landscape in which they lived.

Collecting gases from thermal springs

         The second focus of 2004 AMASE was to sample the ice and rocks in a small cave near the top of Sverrefjell Volcano. It was an exciting climb to near the top of this 525 m volcano. Perched precariously on a ridge top, we deployed the microbial instruments, the UV fluorescent probe, and I collected samples for nutrients and isotopes. Hans Amundsen hacked into the ice with a sterilized ice axe, and the team bagged a substantial chunk of ice to be shipped back frozen to the United States, apropos of sample return from Mars. The microbe team found elevated levels of ATP and LAL-luminescence in the ice relative to surrounding rocks. Their PCR results indicated eubacterial and Archael genes. In the breccia surrounding the ice, we identified genes amplified from sulfate reducing bacteria. Similar genes were not found within the ice. These samples were particularly interesting because they surrounded the layered carbonate found on earlier trips by Amundsen and Treiman. Organic carbon in these samples was <0.1%, a very low amount. They also contained carbonate carbon with isotope values of indicating that these carbonates were precipitated in freezing conditions under glacial ice, perhaps with mantle-derived CO₂.