Bicarbonate uptake by Southern Ocean phytoplankton
Bicarbonate uptake by Southern Ocean phytoplankton
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DOI：
10.1029/2003gb002116
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发表时间：
2004-04-10
影响因子：
5.2
通讯作者：
Popp, BN
中科院分区：
文献类型：
--
作者：
Cassar, N;Laws, EA;Popp, BN
海洋浮游植物有可能大大缓冲未来大气二氧化碳水平的增加。然而，为了使CO2施肥对深海的碳封存产生影响，溶解CO2的增加必须刺激初级生产力;也就是说，海洋光养生物必须是CO2限制的[Riebesell等人，1993年]。因此，需要估计海洋中碳酸氢盐（HCO 3-）的吸收程度，以确定人为碳源是否会增加深海的碳通量。使用短期（CO2）-C-14-不平衡实验在南大洋铁实验（SOFeX），我们表明，HCO 3-吸收南大洋浮游植物是显着的。由于海洋中大部分溶解的无机碳（DIC）是碳酸氢盐的形式，因此生物泵可能对人为CO2不敏感。观察到的DIC摄取约有一半可归因于直接HCO 3摄取，另一半是由被动扩散或主动摄取机制介导的直接CO2摄取。与铁施肥相关的生长速率的增加和CO2浓度的降低并没有引发DIC采集模式的任何明显变化，表明在大多数环境条件下，碳浓缩机制（CCM）是组成性的。低CO2处理诱导增加CO2的吸收，这是由于细胞外碳酸酐酶活性增加，在直接跨质膜HCO 3运输的费用。同位素不平衡实验结果与本研究和其他研究的南大洋碳稳定同位素分馏数据一致。虽然铁施肥已被证明可以显着提高浮游植物的生长，并可能增加碳通量的深海，在这项研究中的浮游植物所采取的无机碳的一个重要来源是HCO 3-，其浓度是可以忽略不计的影响，在CO2的人为上升。我们的结论是，在这个地区的世界海洋的生物生产力是不太可能直接调节自然或人为的变化，大气中的CO2浓度，因为存在一个组成CCM。
Marine phytoplankton have the potential to significantly buffer future increases in atmospheric carbon dioxide levels. However, in order for CO2 fertilization to have an effect on carbon sequestration to the deep ocean, the increase in dissolved CO2 must stimulate primary productivity; that is, marine phototrophs must be CO2 limited [Riebesell et al., 1993]. Estimation of the extent of bicarbonate (HCO3-) uptake in the oceans is therefore required to determine whether the anthropogenic carbon sources will enhance carbon flux to the deep ocean. Using short-term (CO2)-C-14-disequilibrium experiments during the Southern Ocean Iron Experiment (SOFeX), we show that HCO3- uptake by Southern Ocean phytoplankton is significant. Since the majority of dissolved inorganic carbon (DIC) in the ocean is in the form of bicarbonate, the biological pump may therefore be insensitive to anthropogenic CO2. Approximately half of the DIC uptake observed was attributable to direct HCO3- uptake, the other half being direct CO2 uptake mediated either by passive diffusion or active uptake mechanisms. The increase in growth rates and decrease in CO2 concentration associated with the iron fertilization did not trigger any noticeable changes in the mode of DIC acquisition, indicating that under most environmental conditions the carbon concentrating mechanism (CCM) is constitutive. A low-CO2 treatment induced an increase in uptake of CO2, which we attributed to increased extracellular carbonic anhydrase activity, at the expense of direct HCO3- transport across the plasmalemma. Isotopic disequilibrium experimental results are consistent with Southern Ocean carbon stable isotope fractionation data from this and other studies. Although iron fertilization has been shown to significantly enhance phytoplankton growth and may potentially increase carbon flux to the deep ocean, an important source of the inorganic carbon taken up by phytoplankton in this study was HCO3-, whose concentration is negligibly affected by the anthropogenic rise in CO2. We conclude that biological productivity in this region of the world's ocean is unlikely to be directly regulated by natural or anthropogenic variations in atmospheric CO2 concentrations because of the presence of a constitutive CCM.