The growth of phytoplankton in the ocean absorbs carbon from the atmosphere via photosynthesis. In much of the Southern Ocean, the growth of phytoplankton is limited by a shortage of the essential trace nutrient iron. Research by ACE scientists and others has demonstrated that fertilisation of the ocean, by the addition of small quantities of iron, has the ability to increase the uptake of CO2 from the atmosphere.
Photo: Ice Algae
Phytoplankton play an important role in carbon sequestration by taking the carbon down with them when they die and sink to the sea floor. The addition of nutrients would increase phytoplankton growth, therefore increasing the amount of CO2 they sequester when they die. Neither the efficacy nor the safety of this approach has been demonstrated.
The Southern Ocean is a target region for this approach to carbon capture and storage because it has abundant macro-nutrients and requires only small additions of iron to stimulate phytoplankton production. Some proponents of this approach have further suggested that, as phytoplankton is at the base of the ocean food web, ocean fertilisation may enhance the productivity of fisheries. However, effective drawdown of CO2 from the atmosphere resulting in its storage in the ocean is yet to be demonstrated. In addition, it is uncertain as to whether fertilisation might lead to unwanted ecosystem changes.
ACE is studying natural iron fertilisation over the Kerguelen Plateau and in sea ice communities to investigate the extent of carbon uptake and ecosystem health. These results will be compared to results from previous deliberate experimental fertilisations. ACE will then assess the efficacy and risks of ocean fertilisation using the field observations, synthesis of data and numerical simulations.
The KEOPS-2 mission is part of this research.
Image: Iron-rich dust storm originating in Central Australia
View: Dr Andrew Bowie discussing the importance of iron in enabling the oceans to absorb carbon from the atmosphere