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 Shetl ands, and investigated for their release of volatile halogenated organ ic compounds (VHOCs). Dibromomethane, bromoform, dibromochloromethane, bromodichloromethane, diiodomethane and chloroiodomethane were identi fied and their rates of release determined. For the first time the rel ease of 1,2-dibromoethane from macroalgae is reported. Of all compound s investigated, bromoform is released in very high rates fi om all spe cies studied, with the highest release rates from the brown algae Desm arestia anceps (3.9 mu g g(-1) wet algal weight d(-1)), Desmarestia me nziesii (1.3 mu g g(-1) wet algal weight d(-1)), Cystosphaera jacquino tii (0.84 mu g g(-1) wet algal weight d(-1)) and Himantothallus grandi folius (0.3 mu g g(-1) wet algal weight d(-1)). Dibromomethane, diiodo methane, dibromochloromethane and I,2-dibromoethane were also major co mpounds, but released at lower rates. Release rates of bromodichlorome thane and chloroiodomethane were very low for most species. Release of VHOCs occurred from all parts of the thallus of the macroalga. The hi ghest rates were measured in species with a high surface-to-volume rat io. This indicates the formation of VHOC in photosynthetically and met abolically active cortex (surface located) cells. The biological role of these substances and their input into the Antarctic environment is discussed.