Non-toxic antifouling activity of polymeric 3-alkylpyridinium salts from the Mediterranean sponge Reniera sarai (Pulitzer Finali).

We studied the antifouling activity and toxicity of polymeric 3-alkylpyridinium salts (poly-APS), isolated from the Mediterranean sponge Reniera sarai. The activity of these natural products was compared to those of zinc and copper complexes of pyrithione, two non-persistent booster biocides successfully used as tributiltyn (TBT) alternatives. Larvae of Balanus amphitrite (cyprids and nauplii) were used to monitor settlement inhibition. Representative species (microalgae Tetraselmis suecica and larvae of Mytilus galloprovincialis) were used in toxicity bioassays. Compared to the booster biocides, poly-APS had lower inhibiting effect on cyprids’ settlement, but exerted a non toxic reversible action of antifouling activity with a very low toxicity against the organisms used in the toxicity bioassays. Although encouraging, these results are still not enough to consider poly-APS as potential antifoulants suitable for applicative use. They however justify possible future efforts to chemically synthesise poly-APS analogues for further tests.