Arctic bugs survive at -27°C
20 August 2014, by Alex Peel
Arctic bugs can survive in frozen ground as cold as -27°C, scientists have revealed.
It is the first time higher-order invertebrates such as spiders, flies and beetles have been found coping in direct exposure to such cold temperatures. Previous lows were between just -5°C and a little below -10°C.
The research, published in the Journal of Thermal Biology, suggests they may be more resilient to climate change than first feared.
Throughout winter, snow cover acts like a thick blanket over polar ground, insulating the soil below from the extremes of the atmosphere above.
But over the coming decades, climate change is expected to trigger a major reorganisation of snowfall across the polar regions. This has led to concerns that key invertebrates, essential to Arctic ecology, could be exposed to temperatures beyond their survival capabilities.
'There has been this prevailing view, almost a dogma, that invertebrates survive winter better under snow cover,' says Professor Pete Convey, of NERC's British Antarctic Survey, who led the research. 'But this has never really been put to the test in real-world conditions.'
'Imagine if humans or our organs and tissues were able to survive until the point just before all our fluids froze solid'
Prof Pete Convey,
British Antarctic Survey
'So that's what we've tried to do here, and our results suggest that, in the communities we've studied, it makes absolutely no difference at all.'
The research was carried out on Svalbard, a Norwegian archipelago in the Arctic Ocean, where for three months in mid-winter the sun remains below the horizon, leaving the islands in round-the-clock darkness. Temperatures plummet to an average -14°C, with extreme lows around -30°C.
In September 2012, the scientists cut 32 soil samples from tundra close to the islands' main town of Longyearbyen, placing sets of eight in each of four snow-depth treatments.
One set was placed on the roof of the University Centre in Svalbard (UNIS), which is free of snow for the duration of winter. Two were deployed in shallow-snow (30 centimetres) and deep-snow (1.3 metres) sites to the East of town. The remaining set was kept at a constant 7°C in the lab.
Half of each set was retrieved, thawed and the invertebrates extracted in late November, and the other half in early March the following year.
Soil temperatures in the exposed roof samples closely mirrored those in the surrounding atmosphere, rapidly fluctuating, and at one point dipping to -27°C.
The samples at the shallow and deep-snow sites stayed relatively warm throughout, averaging -3.2°C and -1.5°C respectively.
But when the samples were gently thawed out in the lab, the bugs seemed to rejuvenate remarkably well regardless of the temperatures they'd been exposed to.
During winter, the animals go into a state of total inactivity, using one of two strategies to survive. The mites, spiders and springtails tend to favour a freeze avoidance technique. They produce similar chemicals as used in anti-freeze products for cars to keep their body fluids liquid as the temperatures plummet.
Other bugs, such as beetles, use a freeze tolerance method, where they encourage small ice crystals to form in a slow, controlled manner between their cells, preventing damage to the cells themselves.
'One of the incredible things we've seen here is that the freeze avoiders seem to survive at just a degree or so above their freezing point,' says Convey.
'Imagine if humans or our organs and tissues were able to survive until the point just before all our fluids froze solid.'
Invertebrates play an important role in polar ecosystems, particularly in the relationships between plants, the atmosphere and soils.
Convey hopes this work will challenge assumptions about their resilience to climate change, and spark a renewed focus on winter ecology in polar environments.
'It's more difficult to do polar research in the winter, but this just gives us a little tease as to how important the winter ecology can be,' he says.
'Our results suggest this community is more robust to changes in snow depth than has widely been accepted. It raises an important question about whether we've been a little bit alarmist in our predictions for these particular communities.'
Peter Convey et al, 'Survival of rapidly fluctuating natural low winter temperatures by High Arctic soil invertebrates', Journal of Thermal Biology, 2014, DOI: 10.1016/j.jtherbio.2014.07.009
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