Waterborne copper disrupts circadian rhythm in red seabream (Pagrus major)

We investigated the effect of copper (Cu) on circadian rhythms in red seabream, Pagrus major, under various concentrations of Cu (10, 20, 30 and 40 μg/L). To examine variability in circadian rhythms, we measured changes in the period 2 (Per2), cryptochrome 1 (Cry1), serotonin and arylalkylamine N-acetyltransferase (AANAT2) proteins. We found that circadian rhythm-related plasma proteins were significantly lower in a high-Cu environment (30–40 μg/L) than in low-Cu concentration (0, 10, or 20 μg/L). Our results indicate that environmental Cu at concentrations greater than 30 μg/L can have deleterious effects on fish circadian rhythms.