FACTORS GOVERNING MERCURY ACCUMULATION IN 3 SPECIES OF MARINE MACROALGAE

Mercury (Hg) accumulation was studied in Fucus vesiculous L., Ulva lactuca L. and Gracilaria verrucosa (Huds.) Papenfuss, sampled in areas of different polluting loads. The Hg concentration in the seaweeds was variable, but interesting trends emerge for the different species. High levels were observed in Gracilaria verrucosa, which are probably associated to the greater productivity of this species and its longer period of immersion through the tidal cycle. The accumulation factors observed between Hg in algae and in solution are of the order of 10(4), for all species studied. The mean Hg levels in the seaweeds show significant intraspecific variability between sites of different pollution, as well as interspecific variability at each site. Microcosm experiments showed a direct relationship between dissolved Hg and the accumulation rate and Hg concentration in the algae.