Aspects of the biogeochemical cycling of sulphur and iodine was examined on the McMurdo Ice Shelf at Bratina Island to investigate the role of glacial melt water ponds as a biogenic source of sulphur or iodine containing gases. Several ponds with different characteristics were investigated with 130 samples of water and benthic mat from 30 different systems collected and analysed for temperature, ... conductivity, pH, chlorophyll a, major anions and concentrations of dimethylsulphide (DMS), together with the precursor dimethylsulphoniopropionate (DMSP) and the oxidation product dimethylsulphoxide (DMSO). The determination of DMS, DMSP and DMSO is related to the biological activity within the ponds. Surface water samples were also collected for analysis of their biogenic iondinated (CH3I, CH2ClI, CH2I2) and brominated (CH2Br2, CHBr3, BrCH2CH2Br, CHBrCl2, CHBr2Cl) volatile hydrocarbons. Seven meltwater ponds were sampled with 6 samples taken over daily intervals from each pond.