铁施肥促进海洋浮游植物和生物碳泵的不确定性

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

摘要:

铁作为浮游植物所必需的微量元素，限制了全球超过三分之一海域的初级生产力，尤其是在高营养盐、低叶绿素海域(high nutrient low chlorophyll，HNLC)。长期以来海洋铁施肥被认为是一项可以降低大气二氧化碳含量的地球工程策略。然而通过13次海洋人工铁施肥(artificial ocean iron fertilization，aOIF)实验发现，铁的额外添加对海洋深层碳输出量的促进作用要显著低于预期。本文简要地总结了碳在海洋和大气中的循环过程，回顾了人工铁施肥实验对生物碳泵和碳通量等的影响，分析了从海洋铁施肥到海洋碳汇关键生物地球化学过程的影响因素。综上分析发现，科学界对生物碳泵过程及其调控机制的认识仍十分浅薄，考虑到海洋铁施肥还会对海洋生态系统带来一定的负面作用，铁施肥能否作为降低大气中CO₂的有效手段，以达到碳中和并缓解温室效应仍需进一步研究。

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.