Glaciers and ice-sheets are increasingly recognized as the homes of surprisingly diverse and active microbial ecosystems. Even the mere prospect of life in Antarctic subglacial lakes, isolated for many millennia, attracts major international attention and investment. However since life certainly flourishes in unusual habitats on glacier surfaces. these should not be overlooked in our attempts to explore microbial biodiversity. Cryoconite holes are one such habitat, formed when rocky dusts are colonized by a diverse and highly active microbial consortium, forming a darkened microbe-mineral aggregate which increases the transfer of the sun's energy to ice and thus accelerates surface melt. My doctoral studies centred on the diversity and functioning of the bacterial community of cryoconite, which is dominated by organisms closely related to taxa in a broad range of habitats world-wide. In stark contrast, of the eukaryotes inhabiting cryoconite on High Arctic glaciers, the most abundant group by biomass, Fungi, appears strongly dominated by two related groups of fungi hitherto unknown to science. These fungi account for 75% of the sequences in collections of fungal DNA extracted from Svalbard cryoconite, and according to microscopy using genetic stains specific to the group, are derived from small ovoid cells attached to debris. Sequenced genes from specific DNA tests for the fungi demonstrate their presence in cryoconite worldwide suggesting a broad geographic range while the absence of affiliated sequences from DNA databases and the failure to detect the group in periglacial habitats imply their restriction to the cryoconite group near the root of the fungal tree of life and provide a crudely estimated divergence during the Neoproterozoic era, which consisted of major world-wide glaciations, including a hypothesized "Snowball Earth". Little else is known about these fungi, tentatively named the "cryomycetes". Therefore, I seek support to detail their evolutionary history, population structure, ecological functions and interactions. Doing so will permit the testing of the hypotheses that i)"cryomycetes" assume a significant role in the functioning of the extant cryoconite ecosystem ii)they form a major new branch on the fungal tree of life iii)cryoconite holes have formed a stable refuge for these fungi over glacial cycles. As a consequence, I anticipate insights into the interactions between cryoconite biodiversity and melting glaciers, both in the present day, and potentially in the postulated transition from a Neoproterozoic "Snowball" to a "Mudball" Earth.

Concerns are growing about how much melting occurs on the surface of the Greenland Ice Sheet (GrIS), and how much this melting will contribute to sea level rise (1). It seems that the amount of melting is accelerating and that the impact on sea level rise is over 1 mm each year (2). This information is of concern to governmental policy makers around the world because of the risk to viability of populated coastal and low-lying areas. There is currently a great scientific need to predict the amount of melting that will occur on the surface of the GrIS over the coming decades (3), since the uncertainties are high. The current models which are used to predict the amount of melting in a warmer climate rely heavily on determining the albedo, the ratio of how reflective the snow cover and the ice surface are to incoming solar energy. Surfaces which are whiter are said to have higher albedo, reflect more sunlight and melt less. Surfaces which are darker adsorb more sunlight and so melt more. Just how the albedo varies over time depends on a number of factors, including how wet the snow and ice is. One important factor that has been missed to date is bio-albedo. Each drop of water in wet snow and ice contains thousands of tiny microorganisms, mostly algae and cyanobacteria, which are pigmented - they have a built in sunblock - to protect them from sunlight. These algae and cyanobacteria have a large impact on the albedo, lowering it significantly. They also glue together dust particles that are swept out of the air by the falling snow. These dust particles also contain soot from industrial activity and forest fires, and so the mix of pigmented microbes and dark dust at the surface produces a darker ice sheet. We urgently need to know more about the factors that lead to and limit the growth of the pigmented microbes. Recent work by our group in the darkest zone of the ice sheet surface in the SW of Greenland shows that the darkest areas have the highest numbers of cells. Were these algae to grow equally well in other areas of the ice sheet surface, then the rate of melting of the whole ice sheet would increase very quickly. A major concern is that there will be more wet ice surfaces for these microorganisms to grow in, and for longer, during a period of climate warming, and so the microorganisms will grow in greater numbers and over a larger area, lowering the albedo and increasing the amount of melt that occurs each year. The nutrient - plant food - that the microorganisms need comes from the ice crystals and dust on the ice sheet surface, and there are fears that increased N levels in snow and ice may contribute to the growth of the microorganisms. This project aims to be the first to examine the growth and spread of the microorganisms in a warming climate, and to incorporate biological darkening into models that predict the future melting of the GrIS. References 1. Sasgen I and 8 others. Timing and origin of recent regional ice-mass loss in Greenland. Earth and Planetary Science Letters, 333-334, 293-303(2012). 2. Rignot, E., Velicogna, I., van den Broeke, M. R., Monaghan, A. & Lenaerts, J. Acceleration of the contribution of the Greenland and Antarctic ice sheets to sea level rise. Geophys. Res. Lett. 38, L05503, doi:10.1029/2011gl046583 (2011). 3. Milne, G. A., Gehrels, W. R., Hughes, C. W. & Tamisiea, M. E. Identifying the causes of sea-level change. Nature Geosci 2, 471-478 (2009).