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THE IMPACT OF BACTERIAL CONSORTIA ON STRESS RESPONSE OF ANTARCTIC PHYTOPLANKTON
The McMurdo Dry Valley lakes, located in the Taylor Valley, Antarctica, are permanently ice-covered lakes that house unique, isolated ecosystems. The organisms that live there need to contend with a variety of stressors and extreme conditions, including low temperatures, limited nutrient availability, and extreme shade. These sites are unique examples of natural gradients of stress. The ice cover prevents mixing, leading to steep chemical gradients, including concentrations of salt, with hypersaline depths and fresh water near the ice. These gradients, along with the lack of macroorganisms and minimal external inputs, make these lakes natural laboratories for studying the relationship between environmental stressors and community interactions. We developed phytoplankton-bacteria enrichment cultures in autotrophic media from samples taken from Lake Bonney at depths of low and high salinity. We then compared stress response in the enrichment cultures versus Chlamydomonas spp. isolates to a salinity gradient. Cultures were grown under a gradient of salinity to observe salt stress. Optical density was used to measure overall growth, photosystem measurements and RT-qPCR were used to measure indicators of stress, and 16s sequencing of the enrichments was done to observe the impacts of stress on the community composition.