A27: A Community Under Siege — Salinity Impact on Phycosphere Communities

The lakes of the McMurdo Dry Valley in Antarctica represent a stable environment with minimal external inputs and highly stratified aquatic ecosystems as a result of perennial ice-covers that prevent wind-mixing and atmospheric gas exchange. This environment imposes various stressors on its microbial communities such as low light, low temperature, and osmotic stress. Microorganisms within these communities form a syntrophic region known as the phycosphere. To investigate the impact of increasing salinity on these organisms, samples were collected from Lake Bonney at depths of 6m and 15m then grown in 0.5L1 media treated with varying salt (NaCl;Sodium Chloride) concentrations. Optical density (OD750) measurements were taken before isolation, quantification, and amplification of DNA via PCR. Next Generation Sequencing using an Illumina MiSeq Desktop Sequencer allowed for determination of bacterial diversity. The generated research question consisted of: do increased salt concentrations impact the growth of green algae and the relative abundance of phycosphere associated prokaryotes? This study is vital to understand both how alterations to the chemocline depth impact primary producers in aquatic systems and to understand how anthropogenic sources of saline runoff could impact terrestrial water reservoirs. Results indicated not only a variation in green algal growth rates but also a shift in phycosphere associated, prokaryotic community composition across varying salt concentrations. Interestingly, these variations in growth rate and relative abundance were not consistent across the two depth samples. By correlating these changes across salinity and depth, it is expected that the orders Flavobacterium and/or Paraglaciaecola have a direct impact on the survivability of green algae as salt stress increases. The continuation of research within pristine environments like Lake Bonney allows for an unfettered look at the impact of climate change and anthropogenic inputs on the ecosystem. The methods involved allowed for a practical look at processes commonly conducted in the field of microbial ecology.

Author(s); Hunter Coon, Microbiology Major

Callie Owens, Microbiology Major

Advisor(s): Rachael Morgan-Kiss, Department of Microbiology