This 9 year dataset contains data on maximum cell abundance of harmful taxa per week in each location, namely, Dinophysis acuta, Dinophysis acuminata, total Dinophysis spp., “Pseudo-nitzschia delicatissima” complex, “Pseudo-nitzschia seriata” complex, total Pseudo-nitzschia spp., Karenia mikimotoi and total Karenia spp. as well as maximum toxin level per week in each location (HY OA, HY DTX1, HY DTX2, PTX1, PTX2) in the period from 1st January 2011 to 31st December 2019. As stated in the script used to process this dataset, This dataset was created for the use in statistical analyses to facilitate investigation into the relationships between toxin and harmful algal events.