The spatiotemporal dynamics of phytoplankton are critical in regulating the global ocean carbon cycle and Earth's climate. Our current understanding of phytoplankton evolution is largely based on surface chlorophyll-a concentrations obtained via satellite remote sensing. However, chlorophyll-a has proven to be a plastic variable, susceptible to environmental stress. Also, phytoplankton growth is not confined to the surface but rather distributed throughout the entire euphotic zone, leading to uncertainties in remote sensing estimates.
In this study, we systematically analyzed phytoplankton phenology in the global ocean using depth-resolved chlorophyll-a and backscatter data collected by Biogeochemical Argo (BGC-Argo) floats. This approach allows us to investigate phenological characteristics such as initiation time, termination time, duration, peak magnitude, and periodic variations with more accurate perspective. We also compared phytoplankton dynamics across high-latitude regions of various ocean basins to explore the differences in bloom-triggering mechanisms. Additionally, biogeochemical impacts associated with blooms were examined by analyzing observations from the multiple chemical sensors mountded by BGC-Argo floats.

phytoplankton bloom, biogeochemical Argo, phenological characteristic, bloom-triggering mechanism