Seasonal changes in benthic diatom community composition in an Antarctic stream related to stream flow

Stream microbial mats are dynamic communities of phototrophic and heterotrophic organisms that develop over intra-seasonal and inter-seasonal time scales. Diatom community composition is influenced by successional processes and scouring events that together act to shape stream benthic habitats. In ephemeral streams of the McMurdo Dry Valleys (Antarctica), previous work has demonstrated that in streams within the Fryxell Lake Basin, the diatom composition in microbial mat communities is determined largely by the annual and historical flow regime. This study found that the relative abundances of locally-occurring diatom species increases under a colder, lower stream flow regime. Conversely, warmer, higher-flow conditions favor widespread diatom species, and concomitant decreases in diatom species diversity occur at either extreme. This study aims to determine changes in diatom community composition at intra-seasonal time scales in microbial mats in Canada Stream, Fryxell Basin. Preliminary results support the finding that brief cold periods favor local diatom species while warmer periods favor widespread species. Furthermore, the results suggest that there is a ‘lag’ period between the occurrence of a cold snap and the changes in diatom diversity and community composition, suggesting that extreme cold events are important disturbance mechanisms shaping diatom community composition in ephemeral stream microbial mats.