Screening of marine algal extracts for anti-settlement activities against microalgae and macroalgae

The ban on the use of TBT-based antifouling paints for boats under 25 m in length has lead to a search for new non-toxic antifoulants. One of the most promising alternative technologies to heavy metal based antifouling paint is the development of antifouling coatings whose active ingredients are naturally occurring compounds from marine organisms. This is based on the principle that marine organisms also face the problem of the presence of epibionts on their own surfaces. In this study, the antifouling activity of a series of aqueous, ethanolic and dichloromethane extracts from thirty algae from the North East Atlantic coast was investigated. The extracts were tested in laboratory assays against species representative of two major groups of fouling organisms, viz. macroalgae and microalgae. The activity of several extracts was comparable to that of heavy metals and biocides (such as TBTO and CuSO4) currently used in antifouling paints and their lack of toxicity with respect to the larvae of oysters and sea urchins suggests a potential for novel active ingredients.