STREAM SEDIMENT PHOSPHORUS CONCENTRATIONS AND THE BIOGEOCHEMISTRY OF LAKES OF THE ANTARCTIC DRY VALLEYS

The McMurdo Dry Valleys of Southern Victoria Land, Antarctica became a Long Term Ecological Research (LTER) site in 1993. Since that time the connections between the hydrology, geology, geochemistry and biology of the region have been closely examined. Annual precipitation in the Dry Valleys averages less than 10 cm/yr and the yearly average temperature is –20ºC, classifying the region as a polar desert, yet Taylor Valley contains three perennially ice-covered lakes; Bonney, Fryxell and Hoare. Water enters the Dry Valley lakes only via glacier melt-water streams that flow for 6-8 weeks during the austral summer. The interaction of the melt water with stream sediments is of particular importance to the biogeochemistry of the lakes. Phosphorus in these aquatic systems comes from the solubilization of sediments. The stream sediment composition influences nutrients in the lakes. In this study, stream sediments were collected from 17 different streams in Taylor Valley and analyzed for P content. Results indicate that sediments from Aiken Creek in the Fryxell basin have the highest amount of P (56 µmol/g) and those from Vincent Stream in the Bonney basin contain the lowest amount of P (11 µmol/g). Stream sediments of the Fryxell basin have a mean P concentration nearly three times that of the Bonney Basin. Previous work has demonstrated a phosphorus deficiency in Lake Bonney, and nitrogen deficiency in Lake Fryxell. The correlation between the P content of many sediments, streams and lakes in a particular basin is notable. The concentration of P found in stream sediment of the different drainage basins may be related to the glacial history of the Taylor Valley, with sediment containing the highest P concentration found in areas that were most recently glaciated. Thus landscape age may exert a great influence on nutrient dynamics in the lakes.