<p>Elevated levels of photosynthetically active radiation (PAR) and ultraviolet radiation (UVR) can impair photosynthesis in aquatic organisms. The availability of nutrients (e.g., N and P) may modulate macroalgal responses to UV stress. In this study, <i>Gracilariopsis lemaneiformis</i> tetrasporophytes were first pre-cultured under three nutrient concentrations (low nutrients (LN): 2.5 μmol L⁻¹ N and 0.13 μmol L⁻¹ P; medium nutrients (MN): 25 μmol L⁻¹ N and 1.3 μmol L⁻¹ P; high nutrients (HN): 250 μmol L⁻¹ N and 13 μmol L⁻¹ P) and then treated with three types of solar radiation (PAR; PAR + UVA, PA; PAR + UVR, PAB) coupled with three light intensity levels (low light (LL): 30 μmol photons m⁻² s⁻¹; medium light (ML): 150 μmol photons m⁻² s⁻¹; high light (HL): 300 μmol photons m⁻² s⁻¹). Elevated nutrient levels significantly enhanced the growth rate, maximum net photosynthetic rate, maximum relative electron transport rate and contents of photosynthetic pigments and UV-absorbing compounds. The HN group exhibited lower relative UV inhibition and a higher repair rate to damage rate&#xa0;ratio than the MN and LN groups, particularly under HL conditions. These findings suggest that nutrient enrichment of seawater could alleviate UV stress in <i>G. lemaneiformis</i> cultivation under higher light intensity conditions, offering a practical strategy to counteract yield declines in nutrient-limited, high-UV marine environments. This study provides insights for sustainable macroalgal aquaculture under combined UV and nutrient stress.</p>