(595a) Effectiveness of Engineered Nanoceria at Inhibiting Thermally-Induced Oxidative Stress in Symbiodinium.

Coral bleaching has been linked to an immune-like response to thermal stress. In this study we tested the antioxidant effects of engineered poly(acrylic acid)-coated cerium oxide nanoparticles (nanoceria) on free-living Symbiodinium, Breviolum minutum. The synthesized nanoceria with primary particle diameters ~4 nm were internalized by B. minutum within 30 minutes and subsequently localized in the cytosol. Nanoceria exposure did not inhibit cell growth over time, and an exponential growth phase was reached by 30 days of exposure. When the cells were held at an elevated temperature of 34°C for 1 hour, increased intracellular reactive oxygen species (ROS) concentrations were measured over time. A ROS scavenging effect of the nanoceria was observed with a 5 fold decrease in intracellular ROS levels in the B. minutum during thermal stress. The presence of nanoceria did not appear to influence nitric oxide concentrations. As a proof of concept, aposymbiotic anemones (Exaiptasia pallida) were incubated with nanoceria-loaded B. minutum. The successful reinfection observed suggests that nanoceria-loaded Symbiodinium could be used to inoculate partially bleached corals to reduce oxidative stress and provide corals with more time to recover and survive bleaching events.