Deciphering copper and zinc leaching from antifouling paints with different operating modes: flux determination and toxicity evidence.

Laboratory experiments were performed using 3 antifouling paints with different operating modes immersed in seawater for 7 days, to estimate copper and zinc fluxes and determine the scale of the related contamination. The toxicity of antifouling paints leachates was also assessed for natural bacterioplanktonic and phytoplanktonic communities. Given the increase in copper and zinc concentrations (4 to 1750-fold enrichment in dissolved Cu and to 7 to 200-fold enrichment in dissolved Zn), a systematic mortality upon phytoplankton was evidenced within 2 days of exposure to leachates produced from 1 h to 2 days of immersion, whatever the paint. This went oppositely with the environmental risks calculated according to European guidelines, demonstrating an acceptable risk for the environment. Considering that 1 h of leaching from a 7 cm2 painted disk polluted 0.5 L of seawater with Cu in our experimental conditions whatever the paint used, we estimated that a painted ship hull of 15 m2 can pollute more than 10 m3 of seawater within the same time. Leachates produced after only 20 min even yielded phytoplankton growth inhibition or mortality for insoluble and self-polishing paints, respectively, shortening the time needed for a freshly painted ship hull of 15 m2 to pollute 10 m3. The bacterioplanktonic community appeared less sensitive than phytoplankton but demonstrated the same hierarchy: the highest toxicity was observed for the insoluble matrix and the lowest toxicity for the soluble one. This study therefore brings added value in terms of biocides flux determination, range of studied paints and concrete toxicity evaluation.