Differential effects of tributyltin and copper antifoulants on recruitment on non-indigenous species
This work was done as part of a B.Sc. Honours degree at the University of NSW. It is one of the few studies to investigate the different opportunities for marine invasion presented by commercial versus recreational vessels.
Hull fouling of commercial ships has been identified as a primary vector for marine invasion throughout the world. To minimise this fouling, paints containing tributyltin (TBT) or copper have been used extensively on the hulls of vessels. In the early 1980s however, TBT was found to have harmful effects on the development and growth of oysters and other molluscs, and its use on vessels <25 m (i.e. mostly recreational craft) was subsequently banned in most developed nations. Consequently for the past 20 years, commercial and recreational vessels have tended to differ in the type of toxic antifouling paints used on their hulls.
In this study, we investigated the effect of these different antifouling paints on the development of sessile invertebrate communities (i.e. fouling organisms, consisting of species of barnacles, sponges, lace corals, etc) and we discriminated between native and non-indigenous species. The perimeters of fibro-cement panels were painted with copper or TBT antifouling paint and recruitment by organisms to the central unpainted area were recorded after five and ten months. The plates were put in Port Jackson in multiple embayments receiving primarily recreational or commercial vessels.
The effect of the copper was reduced after ten months, while the effect of TBT remained relatively constant. Copper-treated plates were found to enhance the early recruitment of several non-indigenous species. In contrast, the TBT-based antifouling paint was highly effective at preventing recruitment of almost all fouling organisms. The only exception to this being seaweeds, which were most abundant in close proximity to TBT paints, and also showed increased recruitment on plates placed in commercial embayments. Recruitment of several native species was greatly reduced by both copper and TBT-based antifouling paints.
Thus, the increased use of copper antifouling paints on recreational vessels, and the accumulation of copper in embayments where large numbers of recreational vessels are moored, may be helping the transport and establishment of copper-tolerant non-indigenous species into NSW estuaries.