SEDIMENTARY PHOSPHORUS CONCENTRATIONS IN LAKE FRYXELL, ANTARCTICA

Taylor Valley (~78°S latitude), Antarctica is a polar desert; water availability is both limited and highly variable. Despite the cold and dry conditions, Taylor Valley is the location of three perennially ice-covered, closed-basin lakes: Bonney, Hoare, and Fryxell. This study focuses on the sediments of Lake Fryxell and their total, organic and inorganic phosphorus concentrations. Unlike other portions of Taylor Valley, the Lake Fryxell basin was actively glaciated during the Last Glacial Maximum. In Taylor Valley, very little phosphorus enters the environment through precipitation or other external sources; therefore, phosphorus in the aquatic system is predominantly introduced through the chemical weathering of geologic materials in ephemeral stream channels where water only flows 6-12 weeks per year. Previous research has demonstrated that due to the unusual flow-dynamics of the streams, chemical weathering rates are relatively high, even when compared to temperate regions.

We have analyzed sediments currently interpreted to be of Holocene age. The mean total and organic phosphorus concentrations in the Holocene section of the core are 36.6 and 11.4 ?mol/g, respectively. This total P value is approximately two times the pre-anthropogenic value for Lake Erie sediments. Vitousek et al. (1997) demonstrated that younger landscapes should yield higher concentrations of phosphorus than older ones; therefore, the ecosystems on the young landscape should be nitrogen limited. Previous nutrient enrichment studies indicated that Lake Fryxell is indeed nitrogen limited. These high concentrations of phosphorus in Fryxell sediments support Vitousek's model. By comparing the phosphorus concentration of this Lake Fryxell sediment core with modern day phosphorus concentrations, information on the evolution of the lake throughout the Holocene can be gained.