Nanoplastics reshape lipid metabolism in marine microalgae with potential ecological consequence

Nanoplastics (NPs) in marine ecosystems have garnered increasing attention for their interference with the physiological processes of aquatic organisms. An in-depth examination of the toxicological responses of Nannochloropsis oceanica, a species vital to marine ecosystems, is essential due to the crucial role of lipid metabolism in carbon sequestration and energy allocation in microalgae. This study analyzed the toxicological responses of N. oceanica to NPs (0.2, 0.5, and 1.5 mg/L) through lipid metabolism and assessed the resulting ecological consequences. NPs inhibited biomass and lipid synthesis in a dose-dependent manner, which was associated with shifts in carbon flux, oxidative stress, and enzyme suppression. Transcriptomic analysis revealed that exposure to ≤ 0.5 mg/L NPs induced metabolic adaptations (such as fatty acid elongation, triacylglycerol biosynthesis, and upregulation of the MAPK pathway) to partially maintain lipid homeostasis. In contrast, exposure to 1.5 mg/L NPs suppressed lipid synthesis, triggered membrane lipid remodeling, and altered carbohydrate metabolism, resulting in decreased total lipid content, reduced neutral lipids, and changes in fatty acid composition. Dietary exposure to juvenile Scapharca subcrenata resulted in decreased feeding rates, suppressed basal metabolism, and alterations in fatty acid profiles. These findings suggested that, despite some adaptive responses, sub-chronic exposure to NPs disrupted key physiological processes and lipid metabolism in primary producers. Such disturbances could propagate through trophic transfer, potentially affecting the overall physiological functions and lipid metabolism of higher trophic consumers. This study provided preliminary evidence of NPs-induced lipid disruption in microalgae and underscored its potential ecological consequences.