The ecology of carbon sequestration in coastal upwelling ecosystems

The biological carbon pump (BCP) transports carbon fixed by phytoplankton into the deep ocean via multiple pathways and leads to net carbon dioxide sequestration. The BCP is very active in highly productive eastern boundary upwelling systems (EBUSs), however, the extent to which climate change will impact this key ecosystem service remains uncertain. While this review and synthesis focuses on results from the California Current Ecosystem (the most extensively studied EBUS), similarities and differences are also noted with the Benguela, Canary, and Humboldt ecosystems. We focus on vertical carbon export mediated by sinking particles (responsible for >half of the BCP in EBUSs), as well as subduction of organic matter and vertically migrating zooplankton and fish. We suggest that a plug-flow-reactor conceptual model can be used to link BCP results with physical circulation changes within EBUSs to predict whether climate change will lead to increased or decreased biologically mediated CO2 uptake.