Progress in alternative antifouling technologies for healthy biodiversity

Abstract

In recent years the influx of tributyltin (TBT) pollutants in marine environment is of great concern. Antifouling (AF) coating release is considered as one of the major sources of TBT contamination. TBT is known to cause adverse negative impacts like bioaccumulation, proliferation of shell deformities, imposex etc. It has been well demonstrated that environmental TBT concentration lesser than 1ngSnl-1 induces ill effects in several sensitive non-targeted marine living organisms. Besides, TBT accumulation in tissues of edible marine organisms and corresponding accumulation in humans is on the increase. Among the Asian countries, high frequency of imposex has been reported in Korea due to TBT toxicity. But survivorship of sensitive planktonic organisms is yet to be studied in detail. The existing local TBT restrictions and proposed international ban on TBT by International Marine Organization (IMO) has greatly helped in the restoration of growth and development of once severely suffered TBT sensitive organisms. In some instances, it was also related to 'green tide' by a hypothesis that the over growth of green algal communities has resulted due to TBT ban. Although Asian countries are major marine aquaculture producers, comparatively lesser initiatives have been incorporated in their national policies to combat TBT usage. It appears that this may be largely due to cost-effectiveness, as TBT coatings have long lasting effects. Many of the available alternative AF technologies are comparatively less effective and not suitable for broad-spectrum applications. In general, short longevity and cost-effectiveness are also a major drawback in alternatives. However, research attempts directed AF compounds extracted from marine natural products exhibit effective AF activity against 'monospecific' foulers. Allelopathic natural deterrent principles involved in these compounds have proved to be an eco-friendly AF technology. Our experimental investigations show that few Korean marine algae have broad-spectrum AF activity par with TBT. From the lessons learnt by many developed countries with regard to TBT crisis and alarming levels of TBT residues persisting in the Asian waters appropriate changes to be made in TBT restriction policies are discussed. Based on the revelations, suggestions were also made for effective means of controlling fouling organisms and to chalk out concrete action plans to check the ever increasing TBT contamination in the Asian waters.