澳大利亚塔斯马尼亚大学Bach L. T.团队在最新研究中报道，全球碳酸盐化学梯度揭示了海洋碱度增强的负反馈。2025年2月12日出版的《自然—地球科学》发表了这项成果。

据悉，海洋碱度增强是一种被广泛考虑的海洋CO2去除方法。碱度增强通过将海水碳酸盐平衡从二氧化碳转向碳酸氢盐和碳酸盐离子，来隔离大气中的二氧化碳。这种再平衡已经被假设为有利于钙化生物，其钙化的增加可能会大大降低碱度增强的效率。

本文利用全球海洋卫星数据，研究了球石藻（一种重要的钙化浮游植物）对海水碳酸盐化学自然梯度的敏感性。研究表明，浮游植物颗粒无机碳与颗粒有机碳的比值，反映了浮游植物钙化与非钙化的平衡，并受到环境驱动因素的影响，包括生物地球化学省内的营养化学计量学和碳基质。然而，在整个生物地球化学省，这一比例通过碳底物可用性和质子抑制钙化的综合影响，而持续与碳酸盐化学相关。研究人员估计，极端的碱度增强可能会促进球石藻的增殖，从而使得到2100年时，海洋碱度增强的CO2去除潜力降低2-29%。

然而，不太极端的碱度增强可能只会减轻对球石藻的不利酸化影响。他们的发现证明了在评估海洋碱度增强效率时，考虑大规模生物地球化学反馈的重要性。

附：英文原文

Title: Global carbonate chemistry gradients reveal a negative feedback on ocean alkalinity enhancement

Author: Lehmann, N., Bach, L. T.

Issue&Volume: 2025-02-12

Abstract: Ocean alkalinity enhancement is a widely considered approach for marine CO2 removal. Alkalinity enhancement sequesters atmospheric CO2 by shifting the seawater carbonate equilibrium from CO2 towards bicarbonate and carbonate ions. Such re-equilibration has been hypothesized to benefit calcifying organisms, whose increased calcification could strongly reduce the efficiency of alkalinity enhancement. Here we use global ocean satellite data to constrain the sensitivity of coccolithophores—an important group of calcifying phytoplankton—to natural gradients of seawater carbonate chemistry. We show that the ratio of particulate inorganic to particulate organic carbon, reflecting the balance of calcifying versus non-calcifying phytoplankton, is influenced by environmental drivers, including nutrient stoichiometry and carbon substrate within biogeochemical provinces. Across biogeochemical provinces, however, this ratio persistently correlates with carbonate chemistry through combined influences of carbon substrate availability and proton inhibition of calcification. We estimate that extreme alkalinity enhancement may promote the proliferation of coccolithophores, thereby reducing the CO2 removal potential of ocean alkalinity enhancement by 2–29% by 2100. However, less extreme alkalinity enhancement may only mitigate for adverse acidification effects on coccolithophores. Our findings demonstrate the importance of considering large-scale biogeochemical feedbacks when evaluating the efficiency of ocean alkalinity enhancement.

DOI: 10.1038/s41561-025-01644-0

Source: https://www.nature.com/articles/s41561-025-01644-0