Uncertainties of ocean iron fertilization in improving the growth of marine phytoplankton and the efficiency of biological carbon pump

Abstract:

Iron, an essential microelement for phytoplankton growth, limits primary productivity in more than one third of the global oceans, especially in the high-nutrient low-chlorophyll (HNLC) sea areas. Ocean iron fertilization has long been considered as a geoengineering strategy to reduce the atmospheric carbon dioxide level. However, 13 experiments of artificial ocean iron fertilization (aOIF) demonstrated that the promotion effect of iron addition on carbon output in the deep ocean was significantly lower than expected. This paper summarizes the cycle of carbon in the ocean and the atmosphere, reviews the effects of artificial iron fertilization experiments on biological carbon pump and carbon flux, and analyzes the factors influencing the marine biogeochemical process from ocean iron fertilization to ocean carbon sink. According to the review, we conclude that the scientific community has limited understanding of the process and regulation mechanism of biological carbon pump. Considering the certain negative effects of ocean iron fertilization on the marine ecosystem, further research needs to be conducted to reveal whether iron fertilization can be adopted to reduce the carbon dioxide in the atmosphere to achieve carbon neutrality and mitigate the current greenhouse effect.