Phytoplankton form the basis of the marine food web and are naturally limited by the availability of certain elements such as nitrogen, phosphorous and iron in the ocean.
Ocean Fertilization approaches aim to add these limiting elements to the upper sunlit layers of the ocean to stimulate phytoplankton growth and photosynthesis. During these processes phytoplankton fix CO2 in their biomass, thereby increasing the carbon uptake of the upper ocean. When the phytoplankton die and their biomass sinks into the deep ocean, the fixed carbon can be stored at depth for 100 years and more.