Countering the Faltering Ability of Warming Oceans to Absorb CO2 by Adding Silica and Other Nanoparticles.

Diatoms play a central role in marine CO2-fixation and the marine food web, yet their survival is increasingly threatened by intensifying marine heatwaves. Here, we demonstrate that engineered nanoparticles (ENPs) can significantly enhance diatom thermotolerance. The diatom Skeletonema costatum pre-exposed to 0.1 mg/L SiO2 NPs exhibited significantly higher survival rates (from 43 to 64-71%), increased biomass, enhanced photosynthetic pigment content, and a bolstered antioxidant system compared to untreated, heat-stressed controls. Multiomics analyses revealed that SiO2 NPs precondition the cells by reprogramming the transcriptome and metabolome, thereby sustaining healthy carbon metabolism, reinforcing cytoskeletal integrity and proteostasis, and activating a coordinated antioxidant response. Mechanistically, SiO2 NPs catalyze mild reactive oxygen species (ROS) generation, which acts as a mild, preconditioning oxidative stress to establish a cellular memory and prepare diatoms for subsequent heat stress. Importantly, preliminary experiments with other ENPs with ROS-generating (Fe2O3 and CuO) or ROS-scavenging (Se and CeO2) properties also improved the thermotolerance of the diatom Skeletonema costatum. This phenomenon was further observed in other diatoms (Thalassiosira weissflogii, Phaeodactylum tricornutum, Cyclotella) and cyanobacteria (Nostoc), suggesting a universal thermal tolerance mechanism. These findings uncover a previously unrecognized role of engineered nanoparticles, highlighting their potential as a tunable strategy to sustain carbon fixation and marine ecosystem stability under global warming.