Bioremediation of marine shrimp wastewater using high-light-tolerant Rose Bengal mutants of Nannochloropsis oceanica offers a climate-resilient method for co-producing eicosapentaenoic acid under warming and flue gas CO₂

This study investigates high-light-tolerant Nannochloropsis oceanica Rose Bengal mutants (RB2 and RB113) for bioremediation of shrimp aquaculture wastewater (SWW) under increased temperature and light, simulating future climate change. Cultivations were performed under 250 μmol photons m^-2·s^-1 with flue gas CO₂ supply. At 18 °C, RB mutants and wild-type (WT) strain showed similar growth. At 25 °C, representative of warming in subtropical and temperate regions, the RB113 mutant outperformed WT and RB2 in terms of biomass accumulation, photosynthetic efficiency, and non-photochemical quenching. Temperature-dependent nutrient removal patterns revealed that while WT effectively removed inorganic nitrogen and phosphorus, RB113 prioritized biomass and lipid production, highlighting a trade-off between remediation and bioresource accumulation. CO₂ capture was estimated at its highest at 25 °C in RB113 (381 tons CO₂ ha/year). On day 2, under initial nitrogen starvation, RB113 produced 9.95 mg/g DW of eicosapentaenoic acid (EPA) with a peak productivity of 2.338 mg/L/day. By day 5, prolonged nitrogen depletion caused EPA to decline to 3.57 mg/g DW, while total fatty acids doubled to 63 mg/g DW, with a dominance of saturated forms, indicating a shift toward storage lipids. These results suggest that RB113 has significant potential as a climate-adapted bioresource, capable of integrating wastewater remediation, carbon capture, and high-value EPA production, without the need for low-temperature induction. As global temperatures rise and aquaculture expands, this climate-resilient method offers sustainable inland marine aquaculture management by reducing nutrient pollution, with additional benefits of mitigating greenhouse gases and transforming wastewater into valuable products.