Uptake and depuration kinetics of dissolved silver were determined in the brown alga Lobophora variegata, using radiotracer techniques. Results indicate that this widely distributed alga could be a useful bioindicator species for surveying silver contamination in tropical environments. Indeed, results showed that the alga readily concentrates silver (algal concentration of silver was 7,000 times higher than in water after a 28-day exposure) and retains it efficiently within its tissues (biological half-life: 72 +/- 4 days).