Several Pseudo-nitzschia species have been reported to produce domoic acid, which is known to involve in the deaths of marine wildlife at various levels within the food web. In order to determine the distribution of Pseudo-nitzschia species/strains over space and time in Taiwan Strait, samples were collected from Nov. 2018 to Apr. 2022. This study also aims to explore which primers reveal higher diversity of Pseudo-nitzschia and provide results more close to the actual quantity of species.
HTS data based on LSU from the Taiwan Strait demonstrated 26 known Pseudo-nitzschia species, and formed 5 distinct clades which did not clustered with any known Pseudo-nitzschia species. HTS data based on LSU from the Dongshan Bay demonstrated 14 known Pseudo-nitzschia species (all were detected in the Taiwan Strait LSU dataset), and formed 2 distinct clades which did not clustered with any known Pseudo-nitzschia species. HTS data based on ITS1 from the Dongshan Bay demonstrated 15 known Pseudo-nitzschia species, and formed 2 distinct clades which did not clustered with any known Pseudo-nitzschia species. Four species (P. caciantha, P. calliantha, P. circumpora and P. limii) were only detected in LSU dataset, and two species (P. brasiliana and P. micropora) were only detected in ITS1 dataset.
The Taiwan Strait LSU dataset showed the toxic species of Pseudo-nitzschia which demonstrated highest relative abundance was P. galaxiae and P. delicatissima. The Dongshan Bay LSU dataset showed the toxic species of Pseudo-nitzschia which demonstrated highest relative abundance was P. delicatissima. While the Dongshan Bay ITS1 dataset showed the toxic species of Pseudo-nitzschia which demonstrated highest relative abundance was P. pungens. One station HX03 in Dongshan Bay in Jun. 2022 was further examined by qPCR and microscopy to compare the reliability of LSU and ITS1 dataset on quantity of Pseudo-nitzschia species. qPCR detected approximately 200 cells L^-1 and 79,091 cells L^-1 of P. delicatissima and P. pungens respectively at the station HX03 in Jun. 2022. While about 30000 cells L^-1 of Pseudo-nitzschia cells were detected by microscopy, thus may suggesting higher reliability of ITS1 dataset on quantity of Pseudo-nitzschia species.

domoic acid, LSU, ITS1, qPCR