Detection of bloom-forming dinoflagellates Karenia mikimotoi and Prorocentrum donghaiense using qPCR assays

The dinoflagellates Karenia mikimotoi and Prorocentrum donghaiense are both important causative species of harmful algal blooms (HABs) in the East China Sea. The ichthyotoxic K. mikimotoi , which occasionally leads to large-scale HABs in the East China Sea, is difficult to be discriminated from other morphologically similar species in the family Kareniaceae by light microscope observation. To improve the accuracy and efficiency in detection of K. mikimotoi , a real-time quantitative PCR (qPCR) assay was developed in this study. The qPCR assay has high specificity and sensitivity, which allows the detection of K. mikimotoi at the lower detection limit of one cell. The qPCR assay target K. mikimotoi , together with another qPCR assay previously developed for P. donghaiense , was applied to study a bloom of dinoflagellates in the coastal waters of Fujian province from April 25 to June 11 in 2019. Cells of K. mikimotoi were detected in about half of the samples, and the maximum abundance was lower than 30 cells L −1 . Abundance of P. donghaiense cells (maximum abundance above 10 6 cells L −1 ) were determined using both qPCR assay and light microscope cell counting, and the results of the two methods were consistent with each other. The qPCR assays of the blooming dinoflagellates offer reliable and accurate approaches for the detection of HABs species.