The large meander of the Kuroshio western boundary current is well known
to influence the local climate, fisheries, and aquaculture by greatly
modulating regional heat transport, but its impacts on biogeochemical
processes remain unclear. Using high-resolution numerical ocean
modelling and long-term observational datasets, we show that the path of
the Kuroshio determines the extent of the shallow nutricline region,
where winter convective mixing replenishes nutrient availability for
subsequent blooms of phytoplankton during spring. During the large
meander phase, this mechanism triggers offshore phytoplankton blooms
that are otherwise absent during the non-large meander phase. The large
meander also modulates the spatial distributions of primary production,
air-sea carbon flux, and export production. These biogeochemical impacts
of the Kuroshio large meander exert bottom-up control on regional marine
ecosystems that is disproportionate to the thermal effect, and therefore
need to be assessed to understand the large meander's overall impacts on
fisheries and aquaculture.