Rapid treatment of vessels fouled with an invasive polychaete, Sabella spallanzanii , using a floating dock and chlorine as a biocide.

Chlorine solution was added to the water encapsulated within a proprietary ‘floating dock’ to treat a vessel infested with the invasive polychaeteSabella spallanzanii. The chlorine was added as sodium dichloroisocyanurate (‘dichlor’) at an initial concentration of 200 mg l−1of free available chlorine (FAC). This concentration killed 99% ofS. spallanzaniiin their tubes during a 4-h exposure in laboratory tests (EC99160 mg FAC l−1). The concentration of FAC in the floating dock declined to ~50 mg l−1after 4 h and < 10 mg l–1after 16 h. Residual FAC was neutralised with thiosulphate at completion of exposure. A sample of 30S. spallanzaniiindividuals collected from the hull after treatment all showed morphological damage and 28 showed no response to touch. Re-examination of the hull after 6 d found no live worms or other fouling organisms. This method provides a cost-effective, rapid means of treating hull fouling. [ABSTRACT FROM AUTHOR]