Research Summary

Biodiversity

With the application of molecular biology techniques to investigate MDV biodiversity, a surprising level of bacterial (Cary et al. 2010, Takacs-Vesbach et al. 2010; Van Horn et al. 2013) and protist (Bielewicz et al. 2011; Xu et al. in review) richness has been revealed Although bacteria comprise a significant proportion of MDV biomass (Takacs and Priscu 1999; Foreman et al. 2007; Stanish et al. 2012), we know relatively little about their physiology and thus about their ecology and roles in biogeochemical cycling.

Wormherder Creek: Ecosystem connectivity and species distribution

Wormherder creek is an ephemeral stream that occurs only during high flow. Located near Lake Bonney in Taylor Valley, in most years this hillside is bone-dry, making it an ideal site to investigate the long-term effects of extreme pulse/press events. The insert (left) shows an experiment that was flooded during the high flow of 2001-02 and 2008-09. We hypothesized that climate driven increases in the frequency and magnitude of high-flow events will lead to increased connectivity and subsequent redistribution of nutrients and biota across the landscape.

Future scenarios

The future of Taylor Valley under projected warming is one of reduced lake ice cover, increased lake volume and reduced soil habitat in the lower valleys. A new model as part of a Maciek Obryk’s PhD thesis is near completion and predicts that under current climate trends (last 10 years), the lakes will start to seasonally ice-out within the next few decades (Fig. 1). This will dramatically increase summer light levels and wind driven mixing, and alter many chemical and biological processes.

Limnological Studies

Lakes are the only perennial liquid water environments in the MDV; they maintain biological activity year-round with food webs dominated by phytoplankton and bacteria (Priscu et al.1999; Vick et al. 2013; Kong et al. 2012). Perennial ice-cover limits turbulent mixing and most lakes are strongly stratified by temperature and salinity (Spigel and Priscu 1998). The major influences on the chemical composition of lakes are their landscape positions and climate history (Lyons et al. 2000; Dore and Priscu 2001).

Pulse-Press Project

Climate warming in polar regions is associated with thawing of permafrost, resulting in significant changes in soil hydrology, biogeochemical cycling, and in the activity and composition of soil communities. While ongoing, directional climate warming can elicit such responses over decadal time scales, their manifestation typically occurs as discrete thawing pulses. Indeed, in the McMurdo Dry Valleys of Antarctica abrupt changes in community structure and biogeochemical cycling in terrestrial and aquatic ecosystems following a summer warming event (Jan.

Metacommunity dynamics in the McMurdo Dry Valleys and beyond

The metacommunity concept is a major advance in ecology because it provides a theoretical framework to link ecological processes with biodiversity patterns at multiple scales. Metacommunities consist of assemblages of interacting species, typically linked over broad spatial scales by ecological processes influenced by spatial dynamics, environmental factors, and species traits. Diversity patterns in a metacommunity are thus influenced by niche-based species-sorting and dispersal dynamics.

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