Limnology of Organic Lake, Antarctica, a meromictic lake that contains high concentrations of dimethyl sulfide

Abstract

Organic Lake in the Vestfold Hills, Antarctica, is a shallow (7.5 m), meromictic, hypersaline lake that contains a microflora of low species diversity. The lake monimolimnion is anoxic but contains no H₂S. Organic Lake has the highest concentrations of dimethyl sulfide (DMS) as yet recorded in a natural aquatic ecosystem. The greatest concentration of DMS in the lake, 97 µg 1^-1, occurs just above the oxic-anoxic interface. Its presence coincides with maximal numbers of the alga Dunaliella sp. and maximal numbers of bacteria. Analysis of head space samples from axenic cultures indicates that Dunaliella sp. is not directly involved in DMS production. A bacterial strain that was isolated from Organic Lake and that produced DMS from sulfur-containing amino acids was presumptively identified as a Halomonas sp.