Eutrophication mitigates Cu-induced inhibition on growth and photosynthetic performance in the marine diatom Thalassiosira weissflogii.

Eutrophication and metal pollution threaten coastal ecosystems, yet interactions between these stressors are insufficiently explored. This study investigated how nitrogen (N) and copper (Cu) levels impact the physiology of the marine diatom Thalassiosira weissflogii. Results indicate that high nitrogen (HN) conditions significantly alleviate copper's inhibitory effects on chlorophyll a (Chl a) synthesis, growth rate (μ), and photosynthetic performance. Under low nitrogen (LN) conditions, high Cu exposure reduced Chl a content and growth rates by up to 72 % and 55 %, respectively, while reductions under HN were less severe (56 % for Chl a, 20 % for growth). Higher relative electron transport rate (rETR) and gross oxygen release by PS II (GO) under HN across Cu concentrations suggest that N enrichment buffers the toxicity of Cu on this diatom by potentially enhancing PSII activity. These findings underscore the role of nutrient-metal interactions in ecosystem management, highlighting how eutrophication may mitigate heavy metal stress in coastal waters.