The dinoflagellate Noctiluca scintillans blooms from April to June in the northwest Taiwan Strait (TWS), but its scales vary interannually. A massive Noctiluca scintillans bloom broke out nearby Pintan Island in April 2022, as confirmed by light microscopy analysis, which affected the local fishery to a certain extent. Chlorophyll data from the MODIS Aqua satellite showed a marked increase in the TWS in April 2022 compared to April 2021. The Zhe-Min Coastal Current (ZMCC), driven by the northeast monsoon in winter, can transport nutrient-rich water into the TWS and promote phytoplankton blooms. The massive phytoplankton bloom provided sufficient food source for Noctiluca scintillans, but the mechanism of the massive Noctiluca scintillans bloom nearby Pingtan Island is not well understood. In this study, we developed a three-dimensional biological-physical model for the TWS: the Finite Volume Coastal Ocean Model (FVCOM) and a Nutrient-Phytoplankton-Zooplankton (NPZ) model were coupled to investigate the influence of external physical forcing on the nutrient, phytoplankton, and zooplankton dynamics in the TWS. This high-resolution coupled model presents the year-round continuous model simulation results from April 2021 to April 2022 and provides a diagnostic analysis of different wind-forcing influences on nutrients and phytoplankton fluxes. The simulation experiments showed that the intensification of the northeast monsoon strengthened the ZMCC, and increased its impact area. The northeast monsoon induced the westward and southward Ekman transport, leading to the onshore/offshore accumulation of phytoplankton and zooplankton. The headland topography of Pingtan Island promoted the accumulation of nutrients and phytoplankton, providing favorable conditions for the bloom of Noctiluca scintillant. The enhancement of the northeast monsoon could be associated with the 3-year lasting La Nina extreme climate event. This study highlights the importance of climate change on Noctiluca scintillans blooms in the TWS and provides the scientific basis for predicting the occurrence of Noctiluca scintillans blooms in the Pingtan sea area. Keywords: Noctiluca scintillans blooms, Modeling, Biological-physical coupling, Taiwan Strait

Primary Presenter: Zhonghao Lin, Nanjing University of Information Science and Technology (linzhonghao761@163.com)

Authors:

Zhonghao Lin, School of Marine Science, Nanjing University of Information Science and Technology, Nanjing 210044, China  (20211209006@nuist.edu.cn)

Xiaotong Yang, School of Marine Sciences, Nanjing University of Information Science and Technology, Nanjing 210044, China   (20201237018@nuist.edu.cn)

Haifeng Gu, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen 361005, China  (guhaifeng@tio.org.cn)