Substrates exposed to the marine environment frequently undergo biofouling, which can result in both pollution and economic losses. Biofouling can be prevented using antifouling paints to inhibit the growth of adherent organisms. Since the ban of tributyltin, most antifouling agents are primarily copper -based mixtures, such as ZnPT and CuPT. To assess the environmental impacts of various antifouling agents, toxicity tests were conducted using the diatoms Skeletonema costatum and Navicula sp. For toxicity assessment, diatoms were exposed to CuSO