Marine Heatwaves Exacerbate the Toxic Effects of Tire Particle Leachate on Microalgae

Additives leached from tire particles (TPs) after entering the marine environment inevitably interact with marine life. Marine heatwaves (MHWs) would play a more destructive role than ocean warming during the interaction of pollutants and marine life. To evaluate the potential risks of TPs leachate under MHWs, the physiological and nutrient metabolic endpoints of microalgae <i>Isochrysis galbana</i> were observed for 7 days while being exposed to TPs leachate at current or predicted concentrations under MHWs. TPs leachate mainly contained Zn and 6-PPD, which could be absorbed by microalgae mostly, especially under MHWs. Additionally, TPs leachate increased the reactive oxygen species content, activated the antioxidant system, impaired photosynthesis and glycolysis, and decreased sugar and protein content. 10 mg/L TPs leachate increased the lipid content and saturation. Meanwhile, microalgae under such TPs leachate were biased toward the synthesis of long-chain fatty acids and <i>Δ8</i> desaturation pathway. MHWs promoted the positive effects of TPs leachate on microalgae growth at the current concentration but exacerbated the negative effects at the predicted concentration. Our study emphasizes the potential risks of TPs leachate to marine primary production systems, especially if accompanied by the increasing intensity and frequency of extreme climate events.