Nutrient enrichment enhances copper stress tolerance in adult sporophytes of Saccharina japonica (Phaeophyceae)
摘要
Copper (Cu) is a typical metal pollutant that is essential for marine organisms in trace amounts but becomes highly toxic at elevated concentrations. Eutrophication, a common environmental issue in coastal regions, further complicates the ecological dynamics. However, limited research has explored the potential interactive effects of Cu pollution and nutrient enrichment on cultivated seaweed. In this study, we investigated the individual and combined effects of nutrient availability (enriched vs. non-enriched seawater) and Cu exposure (natural seawater as control; 0.2 μmol L−1, LCu; 0.5 μmol L−1, MCu; 1 μmol L−1, HCu) on the growth, photosynthetic activity, and biochemical composition of adult sporophytes of Saccharina japonica. The results indicated that under non-enriched nutrient conditions, the addition of 0.2 μmol L−1 Cu had no significant effect on growth or most of chlorophyll fluorescence parameters, indicating a neutral effect of low-dose Cu. In contrast, exposure to 0.5 and 1 μmol L−1 Cu under non-enriched nutrient conditions resulted in reduced growth, maximum quantum yield, maximum relative electron transfer rate, and soluble carbohydrate content. However, nutrient enrichment mitigated the inhibitory effects of high Cu concentrations. These findings indicate that the effects of Cu on adult S. japonica are dose-dependent and modulated by nutrient availability, with eutrophication potentially enhancing tolerance to high Cu toxicity. These results provide valuable insights into Cu toxicity assessment in seaweed farming and highlight the importance of considering interactions among environmental factors.