Influence of light conditions on the release of volatile halocarbons by Antarctic macroalgae

Four species of red and green Antarctic macroalgae were exposed to various photon fluxes for periods of 6.45 and 17.45h, respectively, and the release of 12 volatile halogenated compounds from chloromethane to diiodomethane was monitored. The results showed that variation of light conditions has an influence on the formation and release of volatile halocarbons, but no clear light-dependent relationships were found. In general, higher release rates were exhibited at no light or low photon fluxes. The higher release rates observed for the methyl halides at short photoperiods suggest that macroalgae could release halocarbons during conditions corresponding to those in the Antarctic winter and may support a concentration build up of these compounds in the environment until spring. Therefore, macroalgae could indirectly contribute to the degradation of the stratospheric ozone layer over Antarctica each year in spring caused by halogens derived from the photochemical destruction of volatile halocarbons.