Image of a Synechococcus elongatus
Electron micrograph of Synechococcus elongatus. Credit: Raul Gonzalez and Cheryl Kerfeld, Wikimedia Commons
Editors’ Highlights are summaries of recent papers by AGU’s journal editors.
Source: Journal of Geophysical Research: Oceans

The surface waters of warm western boundary currents are poor in nutrients. Therefore, intrusions of these nutrient-depleted water into the region are considered to reduce biological production. Although warm waters of the Kuroshio, one of the western boundary currents, often intrude into the South China Sea through the Luzon Strait, their biogeochemical consequences are not well understood.

Li et al. [2025] use data from 20 cruises conducted in the South China Sea between 2004 and 2015, reveal that the Kuroshio intrusion counterintuitively increases the chlorophyll pigments that are contributed by small phytoplankton called picophytoplankton and nanophytoplankton. Previous studies have pointed out that global warming has weakened the Kuroshio intrusion into the South China Sea. Therefore, this study raises concerns that global warming would cause a decrease in primary production in the future.

Schematics of the study showing surface chlorophyll concentration, which is proportional to phytoplankton biomass and abundant in the mixed water property between South China Sea (KI=0%) western Pacific (KI=100%), is intensified with strong Kuroshio intrusion (blue curve) in the South China Sea. Credit: Li et al. [2025], Figure 9

Citation: Li, W., Shang, Y., Li, C., Xu, C., Laws, E. A., Liu, X., & Huang, B. (2025). A stronger Kuroshio intrusion leads to higher chlorophyll a concentration in the northern South China Sea. Journal of Geophysical Research: Oceans, 130, e2024JC021389. https://doi.org/10.1029/2024JC021389

—Takeyoshi Nagai, Editor, JGR: Oceans

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