Effects of the copper-based antifouling paint "Fabi" on growth of the red alga Ceramium tenuicorne

Abstract: The antifouling paint Fabi 3959 is painted on the hulls of vessels to avoid fouling caused by marine organisms attached to surfaces. The paint is registered for use on pleasure boats and other vessels weighing over 200 kg which are mainly running on the Swedish west coast (www.kemi.se). Fabi 3959 contains copper as its active component, which is highly toxic to marine organisms and thus classified as a biocide. Fabi antifouling paint was tested under laboratory conditions on the red macro alga Ceramium tenuicorne, in natural brackish water taken from the Baltic Sea. The Ceramium growth inhibition-test was performed using cloned algae exposed to leakage water with and without sediment. The samples containing only water held concentrations in the range of 0.11% of volume-18% of volume per liter, while the samples using sediment held doses measuring between 0.11% of volume-36% of volume leakage water per liter. The study showed a growth inhibiting effect on the Ceramium in both water and sediment samples down to the lowest concentration used in the test. There was a difference between the water series and the sediment series in the EC50 values of the leakage water. The mean EC50 value was almost 10 times lower within the sediment series compared to the water series (0.114±0.10 and 1.024±0.75, respectively). This indicates that the sediment series are more toxic to Ceramium than the water series. However, if the mean values of EC50 are expressed as copper-concentration, there is no clear difference between the two series (0.59 ± 0.13µg/l for the sediment series and 0.62 ± 0.12 µg/l for the water series). Apparently, the test did not indicate that the sediment was absorbing the copper. Instead it cannot be excluded that another substance involved could have a growth inhibiting impact on Ceramium.