Effect of Different Nitrogen Nutrients on DMSP Content in Emiliania huxleyi and Phaeodactylum tricornutum

Dimethylsulfoniopropionate (DMSP) is one of the most important organic sulfur compounds on Earth, and its significance in global sulfur cycling and climate regulation cannot be overlooked, as it plays an indispensable role in these processes. Phytoplankton are the major producers of DMSP in the marine environment, and nitrogen nutrients are key factors influencing the production of DMSP in phytoplankton. This study focused on two algal species, Emiliania huxleyi (a high DMSP producer) and Phaeodactylum tricornutum (a medium DMSP producer), and conducted indoor culture experiments to compare and analyze the content of particulate DMSP (DMSPp) in the algal culture media under different nitrogen nutrient concentrations and types. The study investigated the relationships between overall DMSPp content, algal density, and DMSPp content per individual algal cell. The results indicated that different nitrogen nutrient concentrations and types had a minimal impact on the content of DMSPp per individual cell in E. huxleyi (P > 0.05), suggesting that the DMSPp concentration in the culture media was mostly influenced by algal cell density. Conversely, different nitrogen nutrient concentrations and types had a significant impact on the content of DMSPp per individual cell in P. tricornutum (P < 0.05), indicating that the DMSPp concentration in the culture media was mainly influenced by the content of DMSPp per individual algal cell. For instance, in the case of P. tricornutum, the average DMSPp content per individual cell in the low NO3– concentration (0 μmol/L) culture group was 11 times greater than that in the high NO3– concentration (1 764 μmol/L) culture group. Furthermore, under different nitrogen nutrient types, the average total DMSPp concentration in NaNO3 culture media was three and four times higher than that in the NH4Cl and CH4N2O culture groups, respectively. These differences may be attributed to variations in the physiological effects of DMSP on different algal species.