The effects of carbon-14 exposure on photosynthetic energy metabolism and carbon metabolism in microalgae

Carbon-14 (¹⁴C) is one of the main radioactive elements in nuclear power plant effluent, but research on its ecological risk remains limited. This study aims to analyze the responses of photosynthetic performance and metabolic profiling in microalgae under ¹⁴C exposure and explore the effect of ¹⁴C on microalgae. The physiological traits results indicated that ¹⁴C inhibited the photosynthesis of Chlamydomonas reinhardtii but promoted the photosynthesis of Chlorella vulgaris. The photosynthetic oxygen evolution rate of C. reinhardtii decreased by 32.6 % in T1 group, and 60.5 % in T2 group. Both Fv/Fm and Pi-Abs values showed a decrease in C. reinhardtii and a increase in C. vulgaris. The combined analysis of transcriptome and metabolome revealed that ¹⁴C exposure significantly affected the photosynthetic energy metabolism and carbon metabolism in microalgae. Photosynthesis and carbon metabolism pathways including pentose phosphate pathway, glycolysis/gluconeogenesis and TCA cycle were significantly affected. According to the transcriptome analysis results, we thought that the up-regulation of photosynthetic genes such as PsbC, PsbE, PsbZ, and Psb28 enhanced the photosynthesis in C. vulgaris. This study can help to evaluate the ecological risk of ¹⁴C and provide reference for the impact of ¹⁴C emissions from nuclear power facilities on aquatic ecosystems.