Low-molecular-weight organoiodine and organobromine compounds released by polar macroalgae - The influence of abiotic factors

The influence of temperature, light, salinity and nutrient availability on the release of volatile halogenated hydrocarbons was investigated in the An tarctic red macroalgal species Gymnogongrus antarcticus Skottsberg. Compare d to standard culture condition, an increase in the release rates of iodoco mpounds was generally found for the exposure of the alga to altered environ mental conditions. Macroalgae exhibited higher release rates after adaptati on for two months to the changed factors, than after short-term exposure. M onitoring the release rates during a 24 h incubation period (8.25 h light, 15.75 h darkness) showed that changes between light and dark periods had no influence on the release of volatile halocarbons. Compounds like bromoform and 1-iodobutane exhibited constant release rates during the 24 h period. The formation mechanisms and biological role of volatile organohalogens are discussed. Although marine macroalgae are not considered to be the major s ource of biogenically-produced volatile organohalogens, they contribute sig nificantly to the bromine and iodine cycles in the environment. Under possi ble environmental changes like global warming and uncontrolled entrophicati on of the oceans their significance may be increase.