Effects of temperature on macromolecular composition of the Antarctic diatom, Corethron pennatum

Southern Ocean temperatures are rising due to climate change. Increasing temperature can alter diatom physiology and survival, subsequently affecting primary productivity and distributions. Diatoms are important primary producers and their composition mediates energy and nutrient transfer to higher trophic levels. Diatom physiology and macromolecular composition are useful indicators for demonstrating and modelling microalgal response to climate change. Using pulse amplitude modulated fluorometry and Attenuated Total Reflectance - Fourier Transform Infrared (ATR-FTIR) spectroscopy, I characterised the physiological response and macromolecular composition of the Antarctic diatom, Corethron pennatum cultured at 0 °C to 5°C. The ATR-FTIR generated data were used to create spectroscopy-based predictive models. The photosynthetic capacity of C. pennatum decreased as temperatures increased, while all cultures eventually failed at 5 °C. As growth temperature increased, unsaturated fatty acid concentrations generally increased, and protein levels decreased slightly. Lipid levels were lowest at the coldest growth temperatures. These findings, particularly the unusual lipid unsaturation at the highest temperatures, show that C. pennatum physiology may differ from many diatoms. Additionally, the model demonstrated a high predictive power (R2 = 0.98), showing that macromolecular composition of C. pennatum is a useful intracellular marker that could be used to model microalgal response to climate change.