Effects of Ocean Acidification on Nitrogen Metabolism of Skeletonema costatum

Ocean acidification (OA), caused by the rising concentration of atmospheric CO 2 , leads to changes in the marine carbonate system. This, in turn, affects the physiological processes of phytoplankton. In response to increased p CO 2 levels, marine microalgae modulate their physiological responses to meet their energy and metabolic requirements. Nitrogen metabolism is a critical metabolic pathway, directly affecting the growth and reproductive capacity of marine microorganisms. Understanding the molecular mechanisms that regulate nitrogen metabolism in microalgae under OA conditions is therefore crucial. This study aimed to investigate how OA affects the expression profiles of key genes in the nitrogen metabolic pathway of the marine diatom Skeletonema costatum . Our findings indicate that OA upregulates key genes involved in the nitrogen metabolic pathway, specifically those related to nitrate assimilation and glutamate metabolism. Moreover, p CO 2 has been identified as the predominant factor affecting the expression of these genes, with a more significant impact than pH variations in S. costatum . This research not only advances our understanding of the adaptive mechanisms of S. costatum in response to OA but also provides essential data for predicting the ecological consequences of OA on marine diatoms.