Physiological and molecular responses of the dinoflagellate Gymnodinium impudicum to phosphorus deficiency: Insights into dissolved organic phosphorus utilization strategies

Abstract

Phosphorus (P) is a vital macronutrient essential for phytoplankton growth. However, in certain oceanic regions, P is often scarce, and numerous studies have demonstrated that dinoflagellates exhibit a robust adaptive capacity, including the utilization of dissolved organic phosphorus (DOP), to cope with P deficiency. In this study, we investigated the physiological and molecular responses of the dinoflagellate Gymnodinium impudicum, a species frequently associated with coastal blooms, to P-deficient conditions, with a focus on its DOP utilization strategies. Our findings reveal that P deficiency significantly inhibits the growth of G. impudicum, and the algal cells likely adapt to P deficiency through phospholipid degradation mechanisms. Among the tested DOP sources, glucose-6-phosphate (G6P), adenosine triphosphate (ATP), and sodium tripolyphosphate (TPP) were able to support the growth of G. impudicum, whereas glyphosate (Gly) was not efficiently utilized. Notably, an increase in alkaline phosphatase activity was observed during cultivation under P-deficient conditions. Furthermore, ATP was assimilated following extracellular degradation, while G6P appeared to be directly absorbed via endocytosis. This study provides critical insights into the adaptive strategies of G. impudicum under P-deficient conditions, offering a theoretical foundation for assessing the potential risks of this species bloom in both P-deficient and eutrophic environments.