The biodiversity of the northern high latitudes is under imminent and serious threat from climate change, according to the recent Arctic Biodiversity Assessment report. Over 21,000 different species inhabit the Arctic, ranging from macrofauna (polar bear, whales, narhals, reindeer) to micro-organisms such as algae, bacteria and lichens.
Specific adaptations required to survive environmental pressures in the Arctic make many species unable to migrate. Moving north would expose them to even more hostile conditions and scarce resources, and moving south requires them to compete with better adapted species. On average, the southern limit of Arctic permafrost has retreated by 39km per year, with a maximum rate of 200km per year in some areas, significantly impacting Arctic flora and fauna.
Here at TTP the interest is primarily on glacier microbes, which are highly susceptible to climate change and underpin Arctic foodwebs. Glacier retreat will ultimately deliver them to proglacial ecosystems where ‘psychrophiles’ will suffer both environmental and competitive stresses, while some ‘cryotolerant’ species may thrive in the warmer, more nutrient rich conditions. Reduced nutrient transformation and community structuring will limit the efficacy of the supraglacial zone as a metacommunity shaping downstream ecosystems. Complex ecological shifts are likely to result from glacier retreat, and the fundamental functioning of Arctic ecosystems will certainly change. One possible outcome is a homogenisation of the global species distribution and overall reduction in biodiversity driven by the decline of endemic species and proliferation of cosmopolitan ones. A warming climate will therefore revolutionise Arctic ecology.
It is not only temperature changes and glacier melt that impacts Arctic microbial communities. Anthropogenic pollutants have been shown to alter modes and rates of microbial activity in a number of ways. Firstly, the delivery of bio-available nitrogenous compounds has inhibited nitrogen fixation in cryoconite communities in Svalbard. Nitrogen fixation requires high energy expenditure and is only carried out by nitrogen fixing bacteria when there is insufficient bio-available nitrogen to support their growth. The identification of Nifh genes but lack of active nitrogen fixation in Svalbard cryoconite holes indicates that despite nitrogen fixing bacteria being present, their growth and proliferation is entirely sustained by nitrogenous contaminants from anthropogenic pollution. Human activity has therefore had a huge impact upon the mechanisms of nutrient cycling in these communities.
Secondly, black carbon, persistent organic pollutants, heavy metals, pesticides and radionuclides originating from industrial emissions and other anthropogenic sources are increasingly deposited on Arctic glacier surfaces. This can significantly alter the biodiversity and community structures of supraglacial ecosystems as well as glacier surface albedo, and the bio-accumulation effects are as yet unknown.
With the Arctic almost certain to continue warming over the foreseeable future, much more research into these topics is required if we are to understand and manage the resultant ecological shifts.