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Bratina Island, despite its name, is not a true island. Instead, it is a large collection of material deposited in an ablation zone on the McMurdo Ice Shelf. Often called "dirty ice", the area encompasses several hundred square kilometers. The largest "island" is known as Bratina and is adjacent to a unique collection of ponds ranging from fresh to hypersaline. These ponds contain a variety of microbial life including cyanobacteria, bacterioplankton, and rotifers.
Many of these ponds are quite shallow and clear, permitting significant penetration of sunlight and exposure to high levels of ultraviolet radiation. To demonstrate and hopefully gain insight into the influence of ultraviolet light on these communities, several experiments were conducted. Acclimation experiments were set up using filters to exclude portions of the UV spectrum. These experiments were sampled weekly for four weeks. Changes in pigment concentration and location, vertical mat migration, species abundance and composition, and rates of photosynthesis were all measured. A second project, carried out individually by two participants, sought to look at UV effects on a particular cyanobacteria, Nostoc sp.
Casten Pond, where the acclimation exposures were performed. |
Cyanobacterial mats after one week of exposure under different solar filters. |
