Dodging Frost Bite
Published in Lab Times 02-2014
Long before man discovers new lands, even the most inhospitable terrain is already taken over by other life forms. Mikael Ohlson, a Norwegian ecologist talks of his icy escapades in search of the first inhabitants of receding glaciers. What are the first creatures to colonize lands covered in ice for centuries?
Let’s take a moment off of the hustle of metropolitan cities and imagine a Scandinavian landscape – say, one like this – snow-capped mountain ranges barely visible from intense fog, strong chilly winds blowing away veils of snow off barren rocks and frosted sheets of ice on a stream of water that may be the only sign of a melting glacier from last summer. This is what you see in a live-webcam of Hardangerjøkulen, one of the six largest glaciers in Norway. At abysmally low temperatures of -25˚C and with 15-20 feet of snowfall for 9 months in a year, Hardangerjøkulen has little human intervention but for precarious getaways of solitary adventurers.
The Midtdaalsbreen glacier at 1400 m above sea level, part of Hardangerjøkulen, has been melting from global warming. Since the year 2000, it has receded by about 150 m exposing cold, desolate land. Now, what can be “happening” around a seemingly lifeless glacier?
For one, Hardangerjøkulen is famous for being the backdrop of George Lucas’ 1977 film Star Wars: The Empire Strikes Back. But for Sigmund Hågvar and Mikael Ohlson, professors of plant ecology at the Norwegian University of Life Sciences in Ås, not far from Oslo, its fame lies in the exciting discoveries emerging from light years past. The two make routine expeditions to the glacial forelands in their quest to observe ecological changes. Their studies have revealed that the icy place is not so lifeless after all – the glacier-retreated areas, laden with organic material, have already attracted their first colonisers. The duo’s findings are truly surprising as they shed light on a novel route for glacier succession by animals (Scientific Reports, 3:2820).
We have all been taught that in any ecosystem there is a directional flow of food, in other words carbon, from plants to animals. It is assumed that plants, the makers of starch, are competent in any new ecosystem. Animals follow suit, now that they can feed on the plants. Then come the carnivores that feed on the herbivores, the decomposers that replenish elemental carbon and so on. But then, are plants always the pioneering organisms in any barren land?
This is not the case at least in glacial forelands. “Cold-loving” terrestrial spiders, beetles and harvestmen are among the first organisms that populate recently deglaciated lands. There’s no evidence of plants here yet, so an all new neighborhood is founded entirely by ‘heterotrophs’, that is, organisms incapable of synthesizing starch. What then is the carbon source for these first-comers?
This paradox has confounded ecologists for a while now, despite some evidence of wind-driven input of prey. Mikael Ohlson with his long-standing interests in ecological changes and expertise in radiocarbon dating has shown that the food actually comes from organic matter released by the melting glaciers themselves.
Finding the answers in nature
Nature may present us with paradoxes but it runs on set principles that can be exploited to find explanations. To understand the evolutionary history of the earth as well as of its inhabitants, geologists and ecologists have for long used the Nobel winning radiocarbon dating technique. The method is based on the principle that there is always a constant proportion of radioactive (C-14) to nonradioactive carbon (C-12) in the atmosphere and allows us to estimate the age of organic material, or even a geological sample, by determining its C-14 content. It is at this same proportion that both C-14 and C-12 enter the foodweb when plants fix carbon during photosynthesis. So given the half-life of its decay, the C-14 content of organic matter at any given time is reflective of its radiocarbon age.
For his studies in the past, on the history of Scandinavian forests and the long-term dynamics of ecosystems, Ohlson has extensively used C-14 dating. For the current paper, his collaboration with Sigmund Hågvar, a devoted expert on insects and professor of nature conservation, led to a novel use of the C-14 dating technique for the study of colonization of glacial forelands. “It is a very small community that uses C-14 to date living organisms to address ecological questions. For the first time, we have used it to identify the age of soil samples and animals collected at the edge of a melting glacier. We sent our samples to Beta Analytic in Miami, Florida, who did the analyses. There has been a huge progress in the method and it is now possible to precisely estimate radiocarbon ages of very little material such as tiny insects, seeds and soil particles”, Ohlson says.
An icy setting
Not many of us scientists actually experience the fun and thrill of working close to nature. Hågvar’s and Ohlson’s scientific endeavor, however, is etched with vivid though frosty, adventure trips to the pristine alpine regions of Hardangerjøkulen. “Our field work was invariably done in the few months in summer, mid-June to mid-August. The weather is inhospitable and there are no roads but only railroads to the mountains. Fortunately for us, the Finse Alpine Research Station in the vicinity helped us a lot with the logistics and offered us a nice play to stay”, they recollect.
During their trips, Ohlson and Hågvar, collected soil samples and insects from the melting edge of the glacier. Back in the lab, they identified the different species in their samples. “Spiders and beetles dominated our collection. We also analyzed the gut content of these “predators” and found that it was enriched in Chironomidae larvae, that of midges”. The duo postulated that these first organisms thrive from organic matter released by the glacier. To confirm their intuitions, they radio-dated the insect samples as well as the soil particles.
The efforts pay off
It came as surprise to the Norwegian researchers when Beta Analytic announced the results of the radiocarbon dating. “We received a very high radiocarbon age of the organic material released by the glacier – a phenomenal 21,000 years! This was a great moment. The material is so far the oldest I have seen in C-14 dating”, exclaims Prof. Ohlson.
The analyses also revealed that ancient carbon from the glacier had been incorporated into present-day aquatic midges (small Orthocladiinae and Tanytarsini species), which have radiocarbon ages of around 1040 years. The predators that ate the midges, such as spiders and beetles, dated between 340 and 1100 years. “We could show that as glaciers melt and large areas become free of ice, the ancient carbon they release plays an important role in the colonization of the barren lands. It represents one of the ways by which ancient carbon trapped in glaciers enters the present day carbon cycle”.
The study thus provides an alternative explanation to resolve a major paradox concerning primary succession of glacial forelands by predators. The authors suggest that the latter is made possible by a local availability of invertebrate prey that feed on ancient carbon released by the melting glacier. It is likely that such pioneering prey-predator establishments fertilize barren land, serving to enhance plant growth in the nascent ecosystem.
From a broader perspective, such studies underscore nature’s ability to cope with unfavorable changes such as global warming. As environmentalists, Hågvar and Ohlson have strong thoughts about global changes and man-made effects on ecosystem processes. With their interests in unravelling forest biodiversity and the role of forests in carbon cycling, they recognise the gravity of forest and fossil fuel conservation. “It is time that we reduced consumption of fossil fuels and took to harvesting solar energy. The sun is our only hope as a long-term energy source for the future,” they conclude.