Navigating stress: Impacts of temperature, polycyclic aromatic hydrocarbons, and heavy metals on the diatom Thalassiosira weissflogii adapted to tropical waters of the Gulf of Guinea

This study evaluated the individual and combined impacts of temperature, pyrene, and cadmium on the coastal diatom Thalassiosira weissflogii under conditions representative of the Gulf of Guinea. In the individual stressor experiments, time, rather than temperature or individual pollutants, was the primary factor influencing growth parameters. Specifically, temperature modulated diatom growth with optimal performance at 28 °C, while 24 °C and 32 °C conditions reduced cell density, chlorophyll-a content, and dry biomass. On the other hand, pyrene significantly affected cell density and dry biomass, while cadmium elicited minimal effects on all measured parameters. In combined stressor experiments, the negative impacts of pyrene and cadmium combinations were more exacerbated at 24 °C and 32 °C, whereas optimal thermal conditions (28 °C) provided partial mitigation from exposure to stressors. These findings highlight the crucial role of temperature in modulating the effects of pollutants on Thalassiosira weissflogii, with combined stress having the greatest impact under non-optimal temperature conditions. Additionally, the study underscores the temperature sensitivity of Thalassiosira weissflogii in tropical ecosystems and offers insights into how the simultaneous stressors of rising ocean temperatures and increasing pollution may affect tropical phytoplankton dynamics and primary productivity. Lastly, the study emphasizes the importance of incorporating thermal thresholds into marine ecosystem models to more accurately predict shifts in coastal and oceanic food webs under climate change scenarios.