McMurdo Dry Valleys LTER - Antarctica
McMurdo Dry Valleys LTER
The McMurdo Dry Valleys (MDVs) (78°S, 162°E) represent the largest (4500 km^2) ice-free area on the Antarctic continent. The MDV landscape is a mosaic of glaciers, soil and exposed bedrock, and stream channels that connect glaciers to closed-basin, permanently ice-covered lakes on the valley floors. Mean annual air temperatures are cold (ranging from -15 to -30°C on the valley floors), and precipitation is low (~50 mm annual water equivalent as snow). Summer air temperatures typically hover around freezing and winter air temperatures are commonly < -40°C. While the water columns of the lakes are liquid and biologically active year round, glacial meltwater streams flow and soils thaw only during the austral summer. There are no vascular plants, but microbial mats are abundant in lakes and streams. Mat organisms are transported by wind onto glacier and lake ice surfaces where they actively metabolize in liquid water pockets (cryoconites) that form during the summer months. In the streams, which desiccate for ~10 months each year, cyanobacterial mats host extensive diatom and soil invertebrate communities. Lakes provide a habitat for diverse phototrophic and heterotrophic plankton communities that are adapted to annual light-dark cycles and temperatures near 0°C. Soils are inhabited by nematodes, rotifers, and tardigrades, all of which are metabolically active during summer. The McMurdo Dry Valleys LTER (MCM) began studying this cold desert ecosystem in 1993 and showed that its biocomplexity is inextricably linked to past and present climate drivers. In the fifth iteration of the MCM LTER program, we are working to determine how the MDVs respond to amplified landscape connectivity resulting from contemporary climate variation.
General Characteristics, Purpose, History
The McMurdo Dry Valleys (MDVs), Antarctica, are a mosaic of terrestrial and aquatic ecosystems in a cold desert that support microbial foodwebs with few species of metazoans and no higher plants. Biota exhibit robust adaptations to the cold, dark, and arid conditions that prevail for all but a short period in the austral summer. The MCM LTER has studied these ecosystems since 1993 and during this time, observed a prolonged cooling phase (1986-2002) that ended with an unprecedented summer of high temperature, winds, solar irradiance, glacial melt, and stream flow (the "flood year"). Since then, summers have been generally cool with relatively high solar irradiance and have included two additional high-flow seasons. Before the flood year, terrestrial and aquatic ecosystems responded synchronously to the cooling e.g., the declines in glacial melt, stream flow, lake levels, and expanding ice-cover on lakes were accompanied by declines in lake primary productivity, microbial mat coverage in streams and secondary production in soils. This overall trend of diminished melt-water flow and productivity of the previous decade was effectively reversed by the flood year, highlighting the sensitivity of this system to rapid warming. The observed lags or opposite trends in some physical and biotic properties and processes illustrated the complex aspects of biotic responses to climate variation. Since then, the conceptual model of the McMurdo Dry Valleys has evolved based on observations of discrete climate-driven events that elicit significant responses from resident biota. It is now recognized that physical (climate and geological) drivers impart a dynamic connectivity among landscape units over seasonal to millennial time scales. For instance, lakes and soils have been connected through cycles of lake level rise and fall since the Last Glacial Maximum, while streams connect glaciers to lakes over seasonal time scales. Overlaid upon this physical connectivity among soils, glaciers, streams and lake are biotic linkages facilitated by the movement of genes, individuals and species through metapopulations and metacommunities. The fifth iteration of the MCM LTER program (MCM5) includes superimposing biotic connectivity upon this linked, heterogeneous landscape. The hypothesis is: Increased ecological connectivity within the MDVs ecosystem will amplify exchange of biota, energy and matter, homogenizing ecosystem structure and functioning. This hypothesis will be tested with new and continuing monitoring and experiments that examine: 1) how climate variation alters connectivity among landscape units, and 2) how biota (species, populations and communities) are connected across this heterogeneous landscape using state-of-the-science tools and methods including ongoing and expanded automated sensor networks, analysis of seasonal satellite imagery, biogeochemical analyses, and next-generation sequencing.
Five six-year NSF funding cycles to date.
Affiliation and Network Specific Information