Spatiotemporal Variations of Phytoplankton Groups and Their Relationships with Mesoscale Eddies in the Northwest Pacific

The complex ocean dynamics in the Northwest Pacific high-seas fishing grounds shape phytoplankton communities, which serve as the foundation for commercially pelagic species. This study investigates how mesoscale eddies modulate phytoplankton groups’ structures by analyzing the spatiotemporal evolution of eight phytoplankton functional types (PFTs) from 2014 to 2023. Utilizing high-resolution AI-driven model data (AIGD-PFT) and a normalized radial distance grid (0–2 R), we quantified PFTs concentrations within cyclonic (CE) and anticyclonic (AE) eddies, validated by Biogeochemical Argo (BGC-Argo) and in situ measurements. Results reveal that diatoms and dinoflagellates dominate the region, accounting for 88.7% of phytoplankton with distinct seasonal peaks in spring and autumn, respectively. CE significantly enhance diatom and dinoflagellate concentration, particularly within the 0.4 R–1.2 R dynamic ring, while AE favor the aggregation of picophytoplankton, such as Prochlorococcus, in mid-to-low latitudes. Correlation analysis indicates that diatom abundance is strongly linked to dissolved oxygen and negatively correlated with sea surface height. We conclude that mesoscale eddies drive the spatial remodeling of phytoplankton communities by altering local physical and nutrient conditions. These findings provide a critical ecological context for assessing the habitat distribution and sustainable management of North Pacific fisheries across different trophic levels.