PhD research of Emily Broadwell
Snowpack and supraglacial surfaces are ephemeral high-light, low-temperature, and low-nutrient environments when compared to other freshwater habitats. During the melt season in these environments when more liquid freshwater is available, snow and glacier algae bloom in the snowpack and glacier surface respectively. Despite being in generally similar habitats, snow and glacier are not closely related phylogenetically, but both are key photosynthesisers in these environments, and so have adapted a range of mechanisms to both harness and protect themselves from the high, yet dynamic, incoming solar radiation.
Some snow algae species utilise a biphasic life strategy, wherein they have a green flagellated early stage and can swim through the snowpack, which can progress to a carotenoid pigment heavy encysted phase where they are more protected from incoming solar radiation. Glacier algae species are different, although they do share the same chlorophyll-based photosystems, they cannot move independently and utilise a much denser phenolic-based pigment. This deflects much of the incoming solar radiation these cells are exposed to. The study of these different adaptations, referring to the physiology of the photosynthetic apparatus within the cell, is termed photophysiology.
Emily Broadwell, PhD student, School of Geographical Sciences, University of Bristol, UK.
Chris Williamson, Lecturer in Polar Microbiology, School of Geographical Sciences, University of Bristol, UK.
Rachel Pickford, MScR student , School of Geographical Sciences, University of Bristol, UK.
This University of Bristol funded PhD research is looking to quantify the variety of photophysiological approaches within and between snow and glacier algae species. This is being done through a combination of laboratory and in-situ studies across the cryosphere to determine the dynamism that these species have. There is also a focus on the genomic controls on these photosynthetic processes, and how these regulate the different adaptations we see in a range of species. As snow and glacier algae blooms can reach many kilometres in diameter and have been found across the cryosphere, understanding how they can change their photosynthetic approaches is crucial in understanding how these may change in the future. By changing their photophysiology, and subsequently, their productivity, these blooms can have a strong influence on nutrient cycling, potentially acting as nutrient reserves in these nutrient poor environments. The changes in pigmentation can also influence physical processes in these environments, as increased pigmentation results in a lower albedo for the snow or surface ice, causing increased solar adsorption and, consequently, increased melt rates.
Watch this space for new project outputs and news….