The Earth Surface Science Institute (ESSI) PhD Projects
Life in the cold: survival in and adaptations to an extreme environment
Supervisor: Liane G. Benning / Martyn Tranter (Bristol)
This project will focus on research which matches ESA’s and NASA's ‘Search for Life” Exobiology Programs that aim to understand the origin, evolution, and distribution of life on Earth and on other planetary bodies. The specific goal of this PhD project is to investigate life’s adaptation to and preservation in modern surface glacial ice and snow, an extreme environment at the edge of Earth’s biosphere and a potential site for biosignatures on other icy planetary bodies.
Rational: Ice and snow are cryogenic vaults for preserving extant biosignatures. Cold temperatures retard the hydrolysis and oxidation of organic materials, thus allowing life to persist for long times. As an analog to ice and snow at the Martian poles and on other icy planets (e.g., Europa), terrestrial glacial ice and snow are not only a harbour for extant life, but also a repository for aeolian materials containing both extant and extinct life signatures. The primary colonisation of snow (and entrapment of cryo-life signals in ice) is an important biogeological scenario, which has clear implications for the detection of life on other planets. A better understanding of the survival strategies adopted by cold-loving organisms (cryophiles) in terrestrial environments is vital for our ability to process data from future planetary missions.
On Earth, cryophiles adopt various strategies to allow them to not just live but thrive under nutrient depletion, temperature fluctuations, dehydration, or high levels of UV-irradiation. They produce a series of compounds including the antioxidants, UV-radiation screening and light-harvesting pigments or they use mineral covers for protective purposes. For example as shown at right, snow algae developed specific pigments (e.g., carotenoids) that shield their chloroplast from the high UV of the arctic, or glycoproteins that allows them to thrive at cold temperatures. However, these adaptations are poorly understood and we know very little about the complexity of the biological inventory contained within snow and ice environments. Consequently, we have little guidance for distinguishing or interpreting biosignatures present in ice/snow settings and this restricts our ability to predict possible life-scenarios on other icy planetary bodies.
This project will address the adaptability and survival strategies of cryophiles (and of snow algae in particular) via a combined field and laboratory approach. During the last 2 summer seasons, an initial sampling of snow and ice habitats at several field sites on the arctic island of Svalbard, Norway (at right) has identified substantial variations in biological and chemical parameters (e.g., distribution, colour, nutrient availability, basic biodiversity etc) associated with the microorganisms at some of the studied sites. However, a quantitatively assessment of the coupled inorganic, microbiological and organic signals is needed. The first aim of this PhD project will be to study the microbial communities in snow fields and glaciers on selected sites on Svalbard and derive a biogeochemical and ecosystem framework (bioactivity, diversity etc) that defines cryo-life habitability parameters. Field samples will be analysed to determine the biological, genetic, mineralogical and geochemical nature of the habitats with respect to composition, diversity, and spatial distribution. The field component of the project will be complemented by lab-based experimental work that aims to quantify the response of snow algae to various stress factors (i.e., UV, desiccation and nutrient stress).
Field and Laboratory approach: (a) sample and fully characterize the molecular constituents of both inorganic and organic signatures of snow and ice samples from distinct glacial zones (accumulation, ablation and superimposed ice) via a new contamination free approach (planetary protection standard, figure at left; Eigenbrode et al 2008); (b) carry out laboratory experiments to address the response of snow algae to UV exposure (UV-A, B and C wavelengths), desiccation and ionic strength (osmotic stress) and nutrient availability (fertilization with and starvation to P and N). From these experiments derive the thresholds and prime parameters controlling snow algae adaptations. The UV and desiccation response will be quantified in bulk via pigment extractions and HPLC analyses, while analyses of single algae via Raman spectroscopy will give us in situ information at the single cell level. The response to nutrient stress will be followed via changes in fluid composition and the nutrient effects will also be correlated with stable isotopic analyses (C, O and N) that will be done via an existing long-term collaboration with US colleagues. In a final stage (most likely in year 3), well characterized laboratory experiments will also be carried out in a simulated Mars Chamber (via a collaboration with the German Space Agency), where UV protective pigment adaptations will be tested in real Mars conditions to cross-validate the field analyses and laboratory experiments.
This combined field and laboratory approach will allow us to develop both field-and lab tested sampling and characterization protocols of life’s adaptations and survival strategies in terrestrial icy settings and provide a comprehensive and combined molecular genetic, spectroscopic/ microscopic and elemental framework of a cryogenic system.
The student: Depending on their background, the student will be trained in a variety of geochemical, spectroscopic or microbiological analyses approaches; many of the field protocols have been thoroughly tested previously but the laboratory approaches (specially the UV stress tests) will be novel and will need original thinking and development; the student will work closely with other cryo-team members both in Leeds and in Bristol.
Logistics: The field part of the project will use facilities at the NERC NERC Arctic Research base in Ny Alesund and also gain access to field sites via the FP7 INTERACT Transnational Access programme.
Further reading material:
[1] Remias et al (2005) Photosynthesis, pigments and ultrastructure of the alpine snow alga Chlamydomonas nivalis. DOI: 10.1080/09670260500202148.
[2] Remias et al (2010) Physiological and morphological processes in the Alpine snow alga Chloromonas nivalis (Chlorophyceae) during cyst formation DOI: 10.1007/s00709-010-0123-y.
[3] Tobler and Benning (2011) The microbial diversity in Icelandic hot springs: temperature, salinity, pH and sinter growth rate effects. Extremophiles 15/4: 473-485;
[4] Eigenbrode et al (2009) A field-based cleaning protocol for sampling devices used in life-detection studies. Astrobiology, 9/4: 455-465;
[5] Stibal et al (2008) Speciation, phase association and potential bioavailability of phosphorus on a Svalbard glacier. Biogeochemistry 90: 1-13.
For application details please see School or Earth and Environment Application website
Application deadline Feb 3rd 2012
Further details and contact Liane G. Benning