February 28, 2007 Biofouling of marine organisms on ship hulls has been a global problem since man crafted the first boat. These days, many marine enterprises suffer the problem and the cost of reducing it, in aquaculture, offshore industries and harbours. In shipping alone, marine biofouling and its most significant organism, the barnacle, increase drag, adversely affect fuel consumption, increase pollution (via the workload on the machinery and downtime due to dry-docking. The annual global cost of cleaning alone is in the billions of dollars. Toxic paints are the most prevalent current anti-fouling strategy but they cause severe environmental disturbances due to the emission of toxic substances into the marine environment. Currently used toxic paints based on Tributyl tin oxide (TBT) are the first target as they generate unwanted effects at non-target organisms and will be banned by 2010, but this ban may be followed by the prohibition of other substances in marine paints. Now a new type of paint has been developed which uses an extract from the microscopic fungus Streptomyces avermitilis to poison barnacles. The fungus lives in the ocean and is extremely poisonous to acorn barnacles and other crustaceans, a feature based on the environmentally friendly defense of the fungus against being eaten. A new study from Goteborg University in Sweden has found that when this fungus is added to paint for ship hulls, the surface remains entirely free from barnacles. As little as a 0.1-percent mixture of pure fungal extract in paint is sufficient to affect the nervous system of barnacles and prevent any growth and the fungal extract is toxic only as long as the paint is on a painted surface. When the paint is dissolved in sea water, the activation of the poison appears not to take place, making the paint apparently harmless to organisms in the open sea.
A sustainable and long-term solution to the persistent problem of toxic emissions resulting from anti-foulants, must be based on methods which are adapted to the environment. At Marine Paint, the objective is to develop anti-foulants which are environmentally acceptable, as well as economically and technically efficient. The catemines provide the basis for the development of environmentally sustainable anti-foulants.
The scientists are basing their work on a theory that the fungal extract makes the paint imitate the fungus’s natural and environmentally friendly defense against being eaten. Hans Elwing also believes that many other organisms in the sea have developed this type of environmentally friendly protection.
“The discovery that this fungal extract counteracts the growth of barnacles will probably create quite a stir around the world. No naturally occurring substance has previously been shown to have such a dramatic effect on barnacles in combination with being so easily degradable in the environment and probably completely safe for humans,” says Hans Elwing, professor at the Department of Cell and Molecular Biology at Göteborg University.
Hans Elwing’s research team has joined up with SP Technical Research Institute of Sweden in Borås and Stockholm to develop their ideas. It is hoped that innovations in nanotechnology will facilitate the creation of new anti-fouling paints for boats.
“The fungal extract is probably both cheaper and, above all, more environmentally friendly that the paints based on copper compounds available on the market today,” says Hans Elwing.