Effects of Three Antifouling Biocides on Marine Biofilm-Forming Bacteria: Highlighting the Need to Monitor Resistance Development When Reducing Active Compound Concentrations. 
Gomez-Banderas, J.; Morreeuw, Z.P.; Fellah, L.; Malouch, D.; Berchel, M.; Jaffrès, P.-A.; Küpper, F.C.; Jaspars, M.; Hellio, C. 
Appl. Sci. 2026, 16, 8138. DOI: 10.3390/app16168138
Published 15 august 2026
 

This study investigated the effects of three antifouling biocides (Sea-Nine 211, CuSO₄ and TBT) on six marine, biofilm-forming bacteria. Bacterial growth and adhesion were evaluated at four concentrations, including environmentally relevant sublethal levels. Sea-Nine 211 exhibited potent antibacterial activity at a concentration of 10 µg/mL; however, lower concentrations promoted adhesion in V. proteolyticus. In contrast, TBT and CuSO₄ exhibited minimal antibacterial activity and increased bacterial adhesion at sublethal concentrations. These results highlight a concentration-dependent response, with reduced antifouling efficacy and a potential risk of bacterial adaptation at low concentrations. A conceptual Resistance Risk Index (RRI) is proposed to support the sustainable management and future assessment of antifouling biocides.