Interactions of dissolved CO2 with cadmium isotopes in the Southern Ocean
Interactions of dissolved CO2 with cadmium isotopes in the Southern Ocean
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DOI：
10.1016/j.marchem.2017.06.010
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发表时间：
2017-10
期刊：
影响因子：
3
通讯作者：
Henricus van Heuven;Steven Abouchami;Wafa Xue;Zichen Galer;Stephen J. G. Rehkamper;M. Middag;Rob van Ooijen;H. J. D. Baara;S. Heuven;W. Abouchami;Z. Xue;S. Galer;M. Rehkämper;R. Middag;J. Ooijen
中科院分区：
文献类型：
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作者：
Henricus van Heuven;Steven Abouchami;Wafa Xue;Zichen Galer;Stephen J. G. Rehkamper;M. Middag;Rob van Ooijen;H. J. D. Baara;S. Heuven;W. Abouchami;Z. Xue;S. Galer;M. Rehkämper;R. Middag;J. Ooijen
在这里，我们报告了有史以来第一次观察到的强相关性，在海洋表面沃茨的溶解δ 114镉与溶解CO2。在南大洋沿着0°W子午线的南极绕极流和威德尔环流，以及威德尔海本身、南极半岛附近和德雷克海峡都观察到这种现象。几个表面水团的这种一致趋势暗示了南大洋内的统一生物化学机制。一个潜在机制的假设是镉在碳酸酐酶将碳酸氢根离子[HCO 3 −]转化为CO2的功能中的作用，后者是仅接受CO2的RuBisCO（核酮糖-1，5-二磷酸羧化酶/加氧酶）所需要的。在低环境[CO2]下，藻类还通过运行碳浓缩机制（CCM）来利用[HCO 3 −]并将其转化为CO2来维持生长。为此，藻类需要更多的酶碳酸酐酶，通常有锌作为其辅因子，但镉可以取代锌，也有镉特异性碳酸酐酶已知的一些浮游植物物种。事实上，在当地浮游生物群落的孵化中，显示浮游植物具有非常强的优先吸收CO2的能力，使得吸收比{[CO2]/[HCO 3 −]}远高于环境海水中的溶解比{[CO2]/[HCO 3 −]}。因此，本文报道的南大洋观测结果也将δ 114 Cd表示为环境海水中{[CO2]/[HCO 3-]}比的函数。建议对南大洋自然沃茨中当地浮游植物的未来研究能够验证Cd在南极浮游植物碳酸酐酶中的作用的假设。
Here we report the first ever observations of a strong correlation in ocean surface waters of the dissolved δ114Cd with dissolved CO2. This is observed in the Southern Ocean along the 0°W meridian in both the Antarctic Circumpolar Current and the Weddell Gyre, as well as in the Weddell Sea proper, near the Antarctic Peninsula and in Drake Passage. This uniform trend in several surface water masses hints at a uniform biochemical mechanism within the Southern Ocean. One hypothesis for the underlying mechanism would be a role of Cd in the carbonic anhydrase function for conversion of bicarbonate ion [HCO3−] into CO2, the latter being required by RuBisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase) that only accepts CO2. At low ambient [CO2] the algae maintain growth by also operating a Carbon Concentrating Mechanism (CCM) for utilization of [HCO3−] and its conversion to CO2. For this the algae need more enzyme carbonic anhydrase that normally has Zn as its co-factor, but Cd may substitute for Zn and there also are Cd-specific carbonic anhydrases known for some phytoplankton species. Indeed in incubations of the local plankton communities it is shown that the phytoplankton have a very strong preferential uptake of CO2, such that the uptake ratio {[CO2]/[HCO3−]} is much higher than the dissolved ratio {[CO2]/[HCO3−]} in ambient seawater. Therefore the here reported observations in the Southern Ocean are also expressed for δ114Cd as function of the ratio {[CO2]/[HCO3−]} in ambient seawater. Future research of local phytoplankton in unperturbed natural waters of the Southern Ocean is recommended to be able to verify the hypothesis of a function of Cd in carbonic anhydrase in Antarctic phytoplankton.