243 Geochemistry (Posters)

Wednesday, 12 October 2011
9:00 AM - 6:00 PM
Hall C

RELATIONSHIPS BETWEEN SOIL GEOCHEMISTRY AND NEMATODE HABITAT SUITABILITY, TAYLOR VALLEY, ANTARCTICA

Paper number: 243-29
Program: Technical Sessions
Time: 9:00 AM – 6:00 PM

Authors

Abstract

Due to the limited influence of surface hydrology, desert environments often preserve spatial variation in soil chemistry that can be linked to landscape history and influence extant ecosystems. Soils in the McMurdo Dry Valleys of Antarctica are among the coldest and driest terrestrial environments. Despite extreme conditions, dry valley soils host low-diversity food webs of microbes, protozoa, and metazoan invertebrates. In most dry valley soils where metazoans are present, communities are composed of a single species, the endemic nematode, Scottnema lindsayae, with additional species occurring less frequently depending upon soil conditions. Much research has focused on moisture and temperature as limitations to geochemical cycling and biological activity, however recent work has demonstrated that soil geochemistry can strongly influence the distribution and functioning of biological communities in the dry valleys. For example, Poage et al. (2008) compiled Dry Valleys-wide nematode occurrence and geochemical data and established soil conductivity and to a lesser degree soil moisture and total soil nitrogen as statistically significant predictors of live S. lindsayae occurrence.

Previous work from sampling transects in the Lake Fryxell, Lake Hoare and Lake Bonney basins in Taylor Valley documented orders of magnitude variation in soil geochemistry on multiple spatial scales. Here we present soil conductivity, moisture, and total nitrogen data from a hectare plot in the Lake Fryxell Basin and show that, at lower elevations, soil chemistry can vary over orders of magnitude on the multi-meter spatial scale, structuring a complex mosaic of favorable and unfavorable nematode habitats. The geochemistry of dry valley soils is fundamentally linked to each valley's complex history, integrating the effects of climate, soil hydrology, glacial activity, lake inundation and recession, atmospheric deposition, and surface age. A strong correlation between soil geochemistry and soil texture suggests a direct linkage between deposition of variably textured sediments deposited during higher lake stands and soil salinity, which strongly influences distribution of nematode communities.