Two tropical macroalgae, Gracilaria salicornia and Padina sanctae-crusis, were exposed to varying concentrations of total Cu and subsequently subjected to photosynthesis-irradiance (P-I) response experiments. The study aimed to determine the effects of total Cu toxicity on the P-I model parameters and growth rate of the macroalgae. The photosynthetic efficiency (α) showed a decreasing pattern w...