Geochemical characteristics of Antarctic lakes and ponds

General characteristics of lakes and ponds, distributions, changes and sources of major ionic components (Na, K, Mg, Ca, Cl and SO_4), nutrients and organic components in lake and pond waters and/or sediments of the McMurdo and Syowa Oases, Antarctica have been discussed from a geochemical viewpoint. Chloride ion contents of lake and pond waters range from 0 17 to 251100 mg/kg Total salt contents show bimodal distributions presumably reflecting the presence and absence of outflows, respectively. Generally, the relative abundances of Na, K, Ca, Mg and SO_4 decrease with increasing Cl contents, indicating that these ionic components deposit during concentration of dissolved salts in lakes and ponds through fractional freezing and/or evaporation of waters. Although contents of nitrate in the coastal lakes and ponds of the Syowa and Vestfold Oases are generally low, those in the oxic zones of the inland lakes and ponds of the McMurdo Oasis are often high Nitrite concentrations in freshwater and saline lakes and ponds are generally low Ammonium, phosphate and/or silicate released by the degradation of settled plankton are generally highly concentrated in the anoxic bottom layers of meromictic lakes because of the paucity of circulation. Total organic carbon or dissolved organic carbon contents in the anoxic layers of meromictic lakes are considerably high, and correlated with Cl contents. Organic matter and dissolved salts are concentrated in the bottom waters due to evaporation and/or freezing concentration of waters Long-chain n-alkanes and n-alkanoic acids (>C_), and C_ sterols are often predominant components in lake and pond water and/or sediment samples in spite of the absence of vascular plants in the areas studied, and indicate that microorganisms are important sources of these compounds. As expected a series of phenolic acids relating to vascular plants are not detected in any Antarctic lake samples