Halocarbon emissions by selected tropical seaweeds exposed to different temperatures

Four tropical seaweeds, Gracilaria manilaensis Yamamoto & Trono, Ulva reticulata Forsskål, Kappaphycus alvarezii (Doty) L.M.Liao and Turbinaria conoides (J.Agardh) Kützing, collected from various habitats throughout Malaysia, were subjected to temperatures of 40, 35, 30, 25 and 20 °C in the laboratory. An exposure range of 21-38 °C is reported for Malaysian waters. The effect of the temperature exposures on the halocarbon emissions of the seaweeds were determined 4 and 28 h after treatment. The emission rates for a suite of six halocarbons commonly emitted by seaweeds, bromoform (CHBr3), dibromomethane (CH2Br2), diiodomethane (CH2I2), iodomethane (CH3I), dibromochloromethane (CHBr2Cl) and dichlorobromomethane (CHBrCl2), were measured using a cryogenic purge-and-trap sample preparation system coupled to a gas chromatography-mass spectrometry. The emission rate of CHBr3 was the highest of the six halocarbons for all the seaweeds under all the temperatures tested, followed by CH2Br2, and CH2I2. The emission rates were affected by temperature change and exposure duration, but overall responses were unique to each seaweed species. Larger decreases in the emissions of CHBr3, CH2Br2, CH2I2 and CHBr2Cl were found for K. alvarezii and T. conoides after 4 h at 40 °C. In both cases there was a >90% (p