Survival of rapidly fluctuating natural low winter temperatures by High Arctic soil invertebrates

Abstract

The extreme polar environment creates challenges for the resident invertebrate communities and the stress tolerance of some of these animals has been examined over many years. However, although it is well appreciated that standard air temperature records often fail to describe accurately conditions experienced at microhabitat level, few studies have explicitly set out to link field conditions experienced by natural multispecies communities with the more detailed laboratory ecophysiological studies of a small number of 'representative' species. This is particularly the case during winter, when snow cover may insulate terrestrial habitats from 3 extreme air temperature fluctuations. Further, climate projections suggest large changes in precipitation will occur in the polar regions, with the greatest changes expected during the winter period and, hence, implications for the insulation of overwintering microhabitats. To assess survival of natural High Arctic soil invertebrate communities contained in soil and vegetation cores to natural winter temperature variations, the overwintering temperatures they experienced were manipulated by deploying cores in locations with varying snow accumulation: No Snow, Shallow Snow (30cm) and Deep Snow (120cm). Air temperatures during the winter period fluctuated frequently between +3 and -24°C, and the No Snow soil temperatures reflected this variation closely, with the extreme minimum being slightly lower. Under 30cm of snow, soil temperatures varied less and did not decrease below -12°C. Those under deep snow were even more stable and did not decline below -2°C. Despite these striking differences in winter thermal regimes, there were no clear differences in survival of the invertebrate fauna between treatments, including oribatid, prostigmatid and mesostigmatid mites, Araneae, Collembola, Nematocera larvae or Coleoptera. This indicates widespread tolerance, previously undocumented for the Araneae, Nematocera or Coleoptera, of both direct exposure to at least -24°C and the rapid and large temperature fluctuations. These results suggest that the studied polar soil invertebrate community may be robust to at least one important predicted consequence of projected climate change.

Size-related mortality during overwintering in cavity-nesting ant colonies (Hymenoptera: Formicidae)

“…Thus, the snow removal resulted simply in a reduction in the periods with snow cover. It is probable that climate change will lead to a reduction in snow cover depth and duration (Christensen et al, 2013;Convey et al, 2015). Thus, snow cover will only protect overwintering animals periodically (as in this experiment), and strong frost, even when short lasting, may result in high mortality.…”

“…Warmer temperatures during winter could increase the chances of survival of overwintering invertebrates (e.g., Bale & Hayward, 2010;Bradshaw & Holzapfel, 2010;Templer et al, 2012, but see also e.g., Sorvari et al, 2011, Haatanen et al, 2015. However, climate change will probably not only affect temperature during winter, but is also likely to result in a reduction in the depth and duration of snow cover (Christensen et al, 2013;Convey …”

Decoupled responses of soil bacteria and their invertebrate consumer to warming, but not freeze–thaw cycles, in the Antarctic Dry Valleys

“…; Convey et al . ), though these results may be influenced by experimental conditions and the specific adaptations of the organisms being studied (Henry ). To further complicate matters, the sub‐lethal effects of long‐term exposure to FTCs are also generally poorly understood in soil communities (Knox et al .…”

“…Low temperatures and FTCs are of particular importance to small, poikilothermic animals such as nematodes, as they are highly susceptible to freeze damage (Bokhorst et al 2012) and have limited capacity to move to potential refugia. Previous field and laboratory studies have revealed differing effects of FTCs on populations of soil microinvertebrates (Bale et al 2001;Sulkava & Huhta 2003;Sjursen et al 2005;Convey et al 2015), though these results may be influenced by experimental conditions and the specific adaptations of the organisms being studied (Henry 2007). To further complicate matters, the sub-lethal effects of long-term exposure to FTCs are also generally poorly understood in soil communities (Knox et al 2016).…”

Soil Moisture Controls the Thermal Habitat of Active Layer Soils in the McMurdo Dry Valleys, Antarctica

“…Soil ecosystems in polar and alpine regions are exposed to a suite of freezing and desiccation stresses. While the ecosystem response to freeze-thaw frequency has been more thoroughly investigated in arctic and boreal regions (e.g., Bale et al, 2001;Bokhorst et al, 2012;Convey et al, 2015;Henry, 2007;Larsen et al, 2002;Schimel & Clein, 1996;Sjursen et al, 2005;Sulkava & Huhta, 2003), relatively little work has been done in Antarctic regions. During the austral summer (December to February), Antarctic active layer soils warm to temperatures above the freezing point of liquid water.…”