Diversity, productivity, and physiology of microorganisms in the stream-moat-lake transition of Lake Bonney, Antarctica

Abstract

Air temperatures exceeding 0°C in Taylor Valley, Antarctica 17-25 degree days each summer and constant solar irradiance melt glacial and lake ice to from liquid water moats at the edges of permanently ice-covered lakes. Moats are fed by glacial streams and interact with comparatively large volumes of ice-covered lake water. This study investigated stream influence on moat chemistry and microbial biomass, productivity and diversity in the moat of East Lake Bonney (ELB) and compared the moat to the ice-covered portion of ELB. Stream inflow was a source of dissolved ions, inorganic carbon (DIC) inorganic nitrogen (DIN), and soluble reactive phosphorus (SRP) to the moat. SRP was rapidly removed in the moat near the stream inflow. Melted ELB ice and biological uptake reduced concentrations of DIN and DIC, resulting in a negative relationship to the inflow. Stream nutrients were correlated with high chlorophyll a and bacterial biomass near the inflow, were positively correlated with bacterial diversity, and negatively correlated with phytoplankton diversity. Correlations between nutrient availability and microbial biomass suggest resource limitation with respect to DIN and SRP, and infer dependence of heterotrophic bacterioplankton on primary productivity.