Antarctic macroalgae - Sources of volatile halogenated organic compounds

Twenty-eight different species of Antarctic macroalgae were collected from December 1991 to February 1992 at King George Island, South Shetlands, and investigated for their release of volatile halogenated organic compounds (VHOCs). Dibromomethane, bromoform, dibromochloromethane, bromodichloromethane, diiodomethane and chloroiodomethane were identified and their rates of release determined. For the first time the release of 1,2-dibromoethane from macroalgae is reported. Of all compounds investigated, bromoform is released in very high rates fi om all species studied, with the highest release rates from the brown algae Desmarestia anceps (3.9 mu g g(-1) wet algal weight d(-1)), Desmarestia menziesii (1.3 mu g g(-1) wet algal weight d(-1)), Cystosphaera jacquinotii (0.84 mu g g(-1) wet algal weight d(-1)) and Himantothallus grandifolius (0.3 mu g g(-1) wet algal weight d(-1)). Dibromomethane, diiodomethane, dibromochloromethane and I,2-dibromoethane were also major compounds, but released at lower rates. Release rates of bromodichloromethane and chloroiodomethane were very low for most species. Release of VHOCs occurred from all parts of the thallus of the macroalga. The highest rates were measured in species with a high surface-to-volume ratio. This indicates the formation of VHOC in photosynthetically and metabolically active cortex (surface located) cells. The biological role of these substances and their input into the Antarctic environment is discussed.