Antifouling activity of azulenoid sesquiterpenes from the antarctic gorgonian Acanthogorgia laxa

Abstract

Biofouling has been recognized as a widespread problem in the design and operation of waterborne structures, with high associated economic costs, for example in ship’s hulls, oil platforms, pipes of cooling systems for power plants, and cages used for aquaculture. In the shipping industry, the economic effects of biofouling are the most dramatic, since fouled hulls produce additional frictional resistance which leads to an increase of up to 40% in fuel consumption. Additionally, shipping activities have been identified as the main source of species introductions in coastal habitats. A vast amount of literature has shown that marine invasive species commonly arrive, not only in the ballast water but also in ballast water sediments and biofouling communities. These are main vectors has led to high percentages of cryptogenic and exotic species in Mar del Plata harbour. Antifouling paints are the most effective method used to prevent fouling settlement. However, they are formulated with toxics which contaminate water and sediments. For these reason, there is a growing need for environmentally safe antifouling systems. In the search for new antifouling compounds, samples of the grey-blue gorgonian Acanthogorgia laxa were collected by bottom otter trawls (-343 m) on board the research vessel ‘Puerto Deseado’ (CONICET) in Antarctic waters (64°41.50S, 63°1.60W). Two azulenoid sesquiterpenes, Linderazulene (1) and Ketolactone (2) isolated from the A. laxa were assayed as potential antifoulants by incorporation in experimental soluble-matrix marine paints. Field tests were conducted at Mar del Plata harbour for 45 days. The results showed that compounds 1 and 2 displayed good antifouling potencies against a wide array of organisms. As always, the marine environment provides knowledge and inspiration for the development of additives for the control of biofouling. In the present work, it was demonstrated that azulenoids can be environmentally friendly natural additives for marine paints.