The McMurdo Dry Valleys (MDV) is a polar desert on the coast of East Antarctica, a region that has not yet experienced the climate warming that is now occurring elsewhere. The MCMLTER project has documented the ecological responses of the glacier, soil, stream and lake ecosystems in the MDV to a cooling trend that occurred from 1986 to 2000, which was associated with the depletion of atmospheric ozone.
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.
Although the abundance and diversity MCM DV biota is low relative to most other ecosystems, recent and ongoing work reveals that representative taxa from most of the major lineages of the Tree of Life are present and functioning.
Microbial mats in Dry Valley streams persist through winter and are revived with summer streamflow (Fig. 1A). Tyler Kohler, PhD student, evaluated controls on mat biomass of 3 mat types (orange, black, and green) to changing hydrology over 20 years by creating smoothed trends from generalized additive mixed models (Fig. 1B) and comparing trends with Pearson Correlation Coefficients.
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.
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).
Over the past decade, we have developed a conceptual model that documents the connectivity of glaciers (primary source of water) to lakes on the valley floor via stream channels.
Aeolian Connectivity: To address our hypothesis that changes in aeolian transport will influence the distribution of soil organisms and ecological connectivity, PhD student Alia Khan is collecting material at about 10 sites in the MDV distributed to identify long range and within valley transport (particle collector installation at right). This research is conducted in collaboration with New Zealand researchers.
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).
Climate driven variations in lake levels since the Last Glacial Maximum have created “resource legacies” seen today as gradients of biogeochemical properties in soils and lakes. Associated with these gradients in organic matter, limiting nutrients, and salts are contemporary organism abundances and biodiversity.