IMPACT OF SALINITY VARIATION ON NATIVE LAKE COMMUNITIES FROM LAKE BONNEY (MCMURDO DRY VALLEYS, ANTARCTICA)

The McMurdo Dry Valleys (MDVs), Antarctica, harbor lakes with year-round liquid water columns isolated under thick permanent ice covers that exhibit extreme conditions (e.g. nutrient deficiency, high salinity, low temperature). Chemistry and biology in the water column have been stratified for hundreds of years, and each lake contains a unique food web dominated by the microbial loop. Warmer summers bring significant environmental change in the form of glacial melt and thinning ice covers. Streams transport glacial melt to the lakes, increasing freshwater input and causing lake level rise. The site of study, Lake Bonney, is hypersaline and the introduction of freshwater (“freshening”) poses a stressor on the high salt-adapted organisms. We used a bioassay approach to investigate the impact of environmentally relevant salinity variation on microbial communities of Lake Bonney. We focused on the responses of three dominant phytoplankton, Isochrysis sp. MDV (haptophyte), Chlamydomonas sp. ICE-MDV (chlorophyte) and Geminigera sp. (cryptophyte). When compared to control conditions, chlorophyte populations were negatively impacted under freshening conditions and had higher abundances under higher salt concentrations. In contrast, haptophytes were abundant under freshening conditions. Our results indicate that major phytoplankton taxa will be significantly impacted by climate-associated melt. The cascading impact of shifts in primary producers on the bacterial communities will be discussed.

Primary Presenter: Rochelle Pereira, Miami University (pereirrp@miamioh.edu)

Authors:

Rochelle Pereira, Miami University  (pereirrp@miamioh.edu)

Rachael Morgan-Kiss, Miami University  (morganr2@miamioh.edu)