The McMurdo Dry Valleys, Antarctica, are a cold desert and represent one of the most inhospitable environments on earth. As a consequence the food webs are simple compared to most other terrestrial ecosystems, and limited to microbes and the nematode Scottnema lindsayae in dry areas, which includes most of the landscape. However, the few wet areas represent hotspots for soil organisms and support a greater diversity of soil fauna, often including the nematode genera Plectus and Eudorylaimus, and a few species of rotifers and tardigrades.

The McMurdo Dry Valleys in Antarctica (MCM) forms one of the most extreme deserts on Earth. It consists of a mosaic of permanently ice-covered lakes, ephemeral streams, exposed soils, and glaciers. Microorganisms are the only life forms occupying these landscape units. Given the relatively low and seasonal growth rates of these organisms, we contend that the distribution of microorganisms within this environment is controlled by physical factors.

Large-scale climate features such as sea level pressures and sea surface temperatures have been shown to influence streamflows in regions around the world. We examined the influence of such features on total annual flows in a summertime glacial meltwater river, the Onyx River, in the ice-free McMurdo Dry Valleys, Antarctica. The 38-year Onyx record is the longest flow record for the continent. The study focused on the December-January climate features.

The MIRADA project was launched in the fall of 2007 to establish a Microbial Biodiversity Survey and Inventory across all 13 of the major aquatic (marine and freshwater) Long Term Ecological Research (LTER) sites in the NSF US LTER Program. The long-term objective of our study is to document and describe baseline diversity and relative abundance data for both common and rare members of microbial communities and to relate this diversity to the underlying physical and chemical environment.

A majority of the research on the MCM LTER occurs during the austral spring and summer (October-January), a period of continuous sunlight, when field support is readily available. Through additional logistical efforts, we were able to collect the first data on the MCM lakes during the transition from summer to winter (October-April). These data allowed us to examine ecosystem responses as photosynthetic input of new carbon stopped. Protein biosynthesis (leucine incorporation) increased in the east lobe of Lake Bonney during March and April (p<0.05).

Streams in the McMurdo Dry Valleys, Antarctica, flow during the short summer melt season (4-12 weeks) when air temperatures are close to the freezing point of water. Because of the extreme low precipitation rates, streams originate from glacial meltwater and flow to closed-basin lakes located on the valley floor. Water samples have been collected from the streams in the dry valleys since the start of the MCM LTER in 1993 and these have been analyzed for major ion and nutrient chemistry. The chemistry of the streams varies by location.

The McMurdo Dry Valleys have no rainfall and most snowfall sublimates before wetting the soils significantly. Glacial melt streams are also seasonal, flowing for only 4 to 6 weeks per year. Consequently, hydrology does not provide significant connections among ecosystem components. Conversely, wind is a persistent daily feature of the McMurdo Dry Valleys environment throughout the year. In summer, cool air from the ice-covered oceans flows into the relatively warm valleys creating a strong thermal gradient in the valleys.

Molecular Identification of Nematode Gut Contents 

Quinn D. Martin, Byron J. Adams

Relative environmental simplicity in the McMurdo Dry Valleys provides an ideal environment for furthering studies of the relationship between biodiversity and ecosystem functioning. Establishing species richness in the Dry Valleys is key to drawing conclusions about this relationship. Antarctic nematode diversity is generally considered to include five main species, only one of which belongs to the genus Eudorylaimus. However, preliminary data suggests the existence of multiple Eudorylaimus species.

 Nematodes are known to play important roles in ecosystem functioning, however their specific roles may vary across different taxonomic levels. Correct identification of nematode species is necessary when analyzing their diversity in order to effectively assign their functional role(s). Several different nematode genera are known to inhabit the dry valleys of the McMurdo LTER, but the ecological roles of each of these taxa is still a mystery. One genus of particular interest is Plectus. The taxonomic diversity of these Antarctic inhabitants is currently in flux.