Harmful algal blooms (HABs) have caused serious issues to ecosystems and human health worldwide, with their frequency and intensity increasing substantially. The present study reports an algal bloom observed in an aquaculture pond near Haizhou Bay in July 2022. The causative species, identified through morphological observation and DNA barcoding analysis, revealed that the algal bloom was induced by the dinoflagellate Levanderina fissa, known for causing extensive HAB events in the coastal waters of China. An abrupt decline in phytoplankton species diversity was observed during the transition from the pre-bloom to the bloom phase. Furthermore, the uptake of four types of dissolved organic phosphorus (DOP), including glucose-6-phosphate (G6P), adenosine-5-triphosphate (ATP), sodium tripolyphosphate (TPP), and glyphosate, by isolated L. fissa were investigated in the laboratory. The results showed that G6P, ATP, and TPP supported L. fissa growth as effectively as orthophosphate. Further, the elevated concentrations of dissolved inorganic phosphorus in the media of the three treatments indicate the participation of extracellular hydrolysis. However, alkaline phosphatase was not the enzyme responsible for the hydrolysis of these three forms of DOP. This study demonstrates that the ability of L. fissa to use DOP may confer a competitive advantage within phytoplankton communities, potentially leading to algal bloom in aquaculture ponds.

harmful algal bloom, Levanderina fissa, species identification, dissolved organic phosphorus