The influence of seawater properties on toxicity of copper pyrithione and its degradation product to brine shrimp Artemia salina

•Toxicity of CuPT to A. salina is lower in seawater with lower salinity.•Salt composition and their proportions influence CuPT toxicity to A. salina.•CuPT's degradation product HPT and Cu2+ in artificial seawater convert to CuPT.•In natural seawater with organic matter less CuPT is formed from a HPT/Cu2+ mixture.•Solely, HPT and Cu2+ are to A. salina less toxic than when tested in combination.

Copper pyrithione (CuPT) is a biocide, used worldwide to prevent biofouling on submerged surfaces. In aquatic environments it rapidly degrades, however, one of the degradation products (HPT) is known to react with cupric ion back to its parent compound. Not much is known about the behavior and toxicity of CuPT and its degradation product HPT in different water systems. Hence, our aim was to investigate the ecotoxicity of CuPT, HPT as well as Cu2+ to the brine shrimp Artemia salina in natural seawater and organic matter-free artificial seawater. Moreover, in order to elucidate the influence of ionic strength of water on CuPT toxicity, tests were performed in water media with modified salinity. The results showed that CuPT was the most toxic to the exposed crustaceans in a seawater media with the highest salinity and with no organic matter content. HPT in a presence of cupric ion converted to CuPT, but the measured CuPT concentrations and the mortality of A. salina in natural water were lower than in artificial water. The toxicity of CuPT to A. salina was significantly influenced by the organic matter content, salinity, and proportions of constituent salts in water. In a combination with cupric ion, non-hazardous degradation product HPT exhibits increased toxicity due to its rapid transformation to its parent compound.