Sources of inorganic carbon for photosynthesis in a strain of Phaeodactylum tricornutum
Sources of inorganic carbon for photosynthesis in a strain of Phaeodactylum tricornutum
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DOI：
10.4319/lo.2002.47.4.1192
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发表时间：
2002-07-01
影响因子：
4.5
通讯作者：
Bidigare, RR
中科院分区：
文献类型：
--
作者：
Cassar, N;Laws, EA;Bidigare, RR
硅藻是海洋浮游植物的重要功能群，因为它们在固定大气二氧化碳（CO2）和将有机碳转移到深水区方面发挥着重要作用。碳浓缩机制，例如活性 CO2 和碳酸氢盐（HCO(3) 以上）吸收和碳酸酐酶活性，被认为对海洋光合作用至关重要，因为主要的碳固定酶 ribulose-1 5-二磷酸羧化酶加氧酶在正常海水 CO2 浓度下低于半饱和状态。 Tortell 等人基于短期无机 C-14 吸收实验。 (1997: Nature 390: 243-244) 最近认为海洋硅藻能够吸收 HCO(3)。然而，正如本文所讨论的。 HCO(3) 超过棒吸收的程度无法根据这些实验进行评估。使用短期 (CO2)-C-14-不平衡实验。我们发现，即使在严格的 CO2 限制条件下，海洋硅藻三角褐指藻的克隆也只吸收很少或不吸收 HCO(3)。预测海洋对 CO2 浓度增加的反应，除其他外，还需要仔细评估海洋藻类吸收 HCO(3) 超过二氧化碳或 CO2 的程度。因为微藻的原质体是气体可渗透的，所有浮游植物都会与生长介质交换 CO2。仅仅与 HCO(3) 超过棒吸收一致的实验结果不足以证明 HCO(3) 超过棒吸收正在发生。我们的结果与基于石油稳定碳同位素分馏数据的预测一致。将同位素不平衡实验与连续生长培养和稳定同位素分馏实验相结合，是了解海洋初级生产者对人为二氧化碳排放的反应以及解释古海洋碳同位素数据的强大工具。
Diatoms are an important functional group of marine phytoplankton because of their role ill the fixation of atmospheric carbon dioxide (CO2) and transfer of organic carbon to deep waters. Carbon-concentrating-mechanisms, such as active CO2 and bicarbonate (HCO(3) over bar) uptake and carbonic anhydrase activity, are believed to be essential to marine photosynthesis, because the main carbon-fixing enzyme, ribulose-1 5-bisphosphate carboxylase-oxygenase, is less than half saturated at normal seawater CO2 concentrations. On the basis of short-term inorganic C-14 uptake experiments, Tortell et al. (1997: Nature 390: 243-244) recently argued that marine diatoms are capable of HCO(3) over bar uptake. However, as discussed herein. the extent of HCO(3) over bar uptake cannot be assessed on the basis of these experiments. Using short-term (CO2)-C-14-disequilibrium experiments. we show that a clone of the marine diatom Phaeodactylum tricornutum takes up little or no HCO(3) over bar even under conditions of severe CO2 limitation. Predicting the response of the oceans to increased CO2 concentrations will require, among other things, a careful assessment of the extent to which marine algae take up HCO(3) over bar or CO2 Because the the plasinalernma of microalgae is gas permeable, all phytoplankton exchange CO2 with the growth medium. Experimental results that are merely consistent with HCO(3) over bar uptake are insufficient to prove that HCO(3) over bar Uptake is occurring. Our results are in accord with predictions based oil stable carbon isotopic fractionation data. Combining isotopic disequilibrium experiments with continuous growth Cultures and stable isotope fractionation experiments is a Powerful tool for understanding the response of oceanic primary producers to anthropogenic CO2 emissions as well as for interpreting paleoceanographic carbon isotope data.