Significance of temperature and salinity in the dynamics of diatoms and dinoflagellates along the coastal Yellow Sea

Diatoms and dinoflagellates are two typical functional groups of phytoplankton, which account for a major part of global primary production and play an important role in ecosystem processes and biogeochemical cycles. It is well known that the dynamics of diatoms and dinoflagellates in the ocean are mainly driven by changes in hydrological conditions related to climate change and human activities. However, little is known about their ability to adapt to changing ocean environments, making it difficult to predict whether and how they will adapt. Analysis of field data from the coastal Yellow Sea (2021–2023) showed that temperature and salinity changes, driven by seasonal variations, notably affected the dynamics of diatoms and dinoflagellates. Moreover, the seasonal dynamics of these two groups exhibited distinct responses to temperature, salinity, and their interactions. Specifically, diatoms exhibited greater heat resistance than dinoflagellates, but were more sensitive to salinity changes, often dominating during the warmer, less saline summer and autumn seasons. In contrast, dinoflagellates, due to their nutritional strategies, showed greater tolerance to salinity changes and often co-dominated with diatoms under high salinity conditions. Overall, changes in temperature and salinity had a large impact on diatoms and dinoflagellates in coastal Yellow Sea, albeit with different relationships. Therefore, future research should focus on the long-term effects of combined temperature and salinity changes, as well as the potential influence of other environmental variables such as nutrient availability.