Upwelling systems are best known for bringing nutrients to the surface. These stimulate phytoplankton blooms, which in turn support important fisheries . However, this deep water also tends to be low in oxygen, which can be further depleted by respiration and surface warming. Prolonged marine heatwaves in the Californian Current hotspot  drove major shifts in the geographic range of birds, mammals, fish, crustaceans, molluscs and other species, and toxic algal blooms .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report