Slow Release Non-Toxic Antifouling Additives for Coatings Used in Aquaculture

The US aquaculture industry, which is around a $2B per year business consisting of 6,343 businesses that employ 15,198 people is greatly in need of a non-toxic and long-lasting antifouling coating. Biofouling is the undesirable accumulation of microorganisms, plants, and animals on man-made surfaces. This biofouling is extremely detrimental to the outdoor marine aquaculture industry. For the netting used in fish pens by farmers and hatcheries, biofouling has been found to rapidly accumulate and fill in the open areas of nets in a matter of weeks. Closing off of open cells of nets leads to huge problems due to the inhibition of water flow that limits availability of dissolved oxygen and restricts the removal of fish excrements and waste that leads to a multitude of problems such as diseases like netpen liver disease, amoebic gill disease, and parasites. Current antifouling paints utilize agents that are toxic to a variety of marine species. The most effective antifoulant agents have been heavy metal based, which are now known to not be environmentally benign. In particular, the very effective tributyltin (TBT) antifoulant additive was banned and totally removed from the market in 2008. The current most popular substitute has been copper oxide, which today can be found in over 400 different marine paints. Although not as toxic as TBT, copper oxide & #39;s toxicity may lead to its eventual ban. Even though copper oxide based paints are still used, it is not totally accepted by many aquaculture farmers and for some cannot be used because of their particular crop & #39;s sensitivity to copper oxide, specifically those raising crabs and scallops. In summary, fouling causes problems for aquaculture farmers and hatcheries that include increased fish mortality, slower fish growth, premature harvesting and increased labor and material costs that translate to lower profitability. In addition to detrimental effects to the fish, the extra weight added to the netting system can be enormous. It has been reported that an increase by a factor of 200 in the weight of the net has been observed, which means a 50 pound net could end up weighing 5 tons after fouling. This often will result in net failures and extra maintenance. Phase I research verified that certain benign antifouling agents added to clays impart antifouling properties when added to marine paint. Phase II work will entail the optimization of the encapsulation, the addition to various other paint matrices for the maximization of the antifouling efficacy while minimizing costs, and in vivo testing at four sites that possess completely different marine environments. Not only will an effective environmentally friendly antifouling paint be very marketable to the aquaculture sector but will also be very attractive to the much larger marine coatings industry for use in coating bottoms of ships and boats.