Marine biofouling, whose global annual costs have been calculated to be about 6,5 billion of dollars, causes ship velocity reduction and dry docks stopping for hull scraping and antifouling protective coating repainting by new antifouling paints containing toxic biocides that gradually released; from their hulls should avoid fouling settlement but contemporarily contributing to environmental pollution, severely in some cases, especially in coastal areas.
The IMO (International Maritime Organisation) judged toxic substances released by antifouling paints as an important source of pollution to be controlled. For this reason this Organisation banned, beginning from 2003, the use of some paints because, although well performing as antifouling, they are harmful for marine environment. This is the case of Tri Butyl Tin based self polishing paints. The ban more than being disappointing for ship and yachting antifouling paints producers and owners, recalled to actuality the research of new and alternative antifouling paints contemporarily effective but not toxic: it seems a contradiction in terms!
The research here presented and carried out in Genova with CNR funds, has evident applicative aims with real economical and environmental values but it is also interesting for public health reasons, taking into account that often recreational boats (but also large ships) stop in the same coastal segregated and protected areas where aquaculture plants are present. It well fits in the research current of bioactive substances, largely used for pharmacological employ, of marine organisms and in particular in those presenting their bodies normally free of epibiotic organisms settled onto.
The original idea is that these 'substratum organisms' possess special defences that, in same way, protect their surfaces against epibiotic settlement that 'sensu lato' may be considered as fouling. On the other hand, being many poisons derived from natural substances, it is necessary to verify if the defensive action is specific, short lasting in time and not toxic for the other organisms.
In cooperation with Ljubljana University, we verified antifouling activity of Polyalchilpyridine salts extracted and purified from the sponge Reniera sarai whose laboratory synthesis is carrying on at present in satisfactory way by Bioorganic Chemistry laboratory of Trento University. These salts, although less active than the two biocides most commonly used in antifouling paints, are from 500 to 2000 times less toxic towards phyto and zooplanktonic not target organisms.
Settling tests to assess antifouling efficacy, have been carried out with settling larvae (cyprid) of the barnacle Balanus amphitrite showing that, after staying in contact with the concentrations effective to prevent settlement, at the end of the experiment, into the solutions with commercial products, they are no more able to settle when back in pure sea water, while those in contact with PolyAlchilPyridine salts, after the same time of staying, maintained unaltered their settlement ability. This indicates a not toxic antifouling activity but a narcotic or 'repellent' one.
Focus