Interactions between Noctiluca scintillans and Three Co-Occurring Microalgae in Response to Varying Nutrient Levels

Abstract

The dinoflagellate Noctiluca scintillans is a globally distributed bloom-forming species. Previous studies have shown that the primary reason for the frequent occurrence of N. scintillans blooms may be the proliferation of microalgae due to eutrophication, which provides a sufficient source of food. Meanwhile, N. scintillans may release nutrients into the environment, thus affecting the population dynamics of microalgae. Thus, to investigate the interaction between N. scintillans and co-occurring microalgae, this study examined the population dynamics of N. scintillans and their interaction with three representative microalgae species in response to varying nutrient levels. The findings indicate that the growth of N. scintillans is slow when co-cultured with diatom Skeletonema costatum. Moreover, a high density and rapid growth rate of S. costatum may have an inhibitory effect on the growth of N. scintillans. Conversely, the population abundance of N. scintillans increased with the rise in the population density and nutritional level of Heterocapsa steinii (dinoflagellate) and Heterosigma akashiwo (raphidophyceae). Notably, N. scintillans can discharge specific nutrients into the aquatic environment, which can subsequently be assimilated and exploited by H. steinii. Thus, the interaction between the species and population dynamics of plankton, as well as changes in nutrient levels within the ecosystem, played a significant role in influencing the growth and population dynamics of N. scintillans. The mutualistic association between N. scintillans and microalgae may establish a transient closed loop, thereby fostering the sustained proliferation and subsequent expansion of N. scintillans.