Stable carbon isotope values in dissolved inorganic carbon of ambient waters and shell carbonate of the freshwater pearl mussel (Hyriopsis sp.)
Stable carbon isotope values in dissolved inorganic carbon of ambient waters and shell carbonate of the freshwater pearl mussel (Hyriopsis sp.)
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环境水中溶解的无机碳和淡水珍珠贝（三角帆蚌）的壳碳酸盐中的稳定碳同位素值
DOI：
10.1007/s10933-015-9834-6
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
A.
中科院分区：
文献类型：
--
作者：
Yoshimura;T.;Izumida;H.;Nakashima;R.;Ishimura;T.;Shikazono;N.;Kawahata;H.;Suzuki;A.
我们利用环境水中溶解的无机碳 (DIC) 和商业养殖淡水珍珠贝 (Hyriopsissp., Unionidae) 贝壳碳酸盐中的稳定碳同位素值 (δ13C) 研究了与霞浦湖（日本）相连的运河中的碳源和循环。 δ13CDIC 与 DIC 浓度、pH、月降水量和 pCO2 呈相关性。因此，碳同位素组成可以用作环境变量的代表。 pCO2 范围为 3,046 至 9,535 µatm，平均值为 6,035 µatm，在整个研究过程中始终远高于大气值。河流中二氧化碳溶解度、放气和生物过程的变化对碳同位素组成的影响很小。 DIC 浓度和 δ13CDIC 主要受土壤外部输入和与降水相关的风化衍生 DIC 控制。帆藻壳不同生长区的 δ13C 值相似，这表明在整个壳形成过程中 δ13CDIC 来源恒定，与尺寸相关的代谢变化对壳 δ13C 的影响可以忽略不计。 DIC 和三角帆蚌壳 δ13C 值的比较表明，贻贝个体发育不影响碳同位素分馏，但标本间差异表明生理因素对三角帆蚌 δ13C 值有系统的控制。结果还表明，如果要从壳 δ13C 值推断河流系统的年平均 δ13CDIC 值，则应采样多个样本，年平均值可得出河流系统稳定同位素组成的时间综合测量值。鉴于环境 DIC 和贝壳之间的碳同位素分馏为 +2.0 ± 0.7 ‰ (2 se)，我们估计 2002 年至 2007 年贝壳生长期间的 pCO2 平均约为 6,850 μatm。所有年份的 pCO2 浓度都比大气平衡值大一个数量级，表明 CO2 从地表水流失到大气中或下游到湖泊。在考虑二氧化碳的区域重新分配时，必须考虑这些损失。我们的结果扩展了淡水双壳类 δ13C 测量的效用，以推断环境水域的 δ13CDI 历史。该工具提供的信息是对直接 δ13CDIC 测量获得的信息的补充，并且应该能够推断关键变量（例如 spCO2）的长期变化。
We investigated carbon sources and cycling in a canal connected to Lake Kasumigaura (Japan) using stable carbon isotope values (δ13C) in dissolved inorganic carbon (DIC) of ambient water and in shell carbonate of the commercially cultured freshwater pearl mussel (Hyriopsissp., Unionidae). The δ13CDICshowed correlations with DIC concentrations, pH, monthly precipitation andpCO2. Thus, the carbon isotopic composition can be used as a proxy for environmental variables. ThepCO2ranged from 3,046 to 9,535 μatm, with a mean value of 6,035 μatm, and remained well above the atmospheric value throughout the years of study. Changes in CO2solubility, outgassing and biological processes in the river had only minor influence on the carbon isotope composition. DIC concentration and δ13CDICwere controlled primarily by external inputs of soil and weathering-derived DIC associated with precipitation. The δ13C values in different growth zones of theHyriopsisshells were similar, suggesting that given a constant δ13CDICsource throughout shell formation, the influence of size-related metabolic variations on shell δ13C was negligible. Comparison of δ13C values in DIC andHyriopsisshell indicated that mussel ontogeny did not influence carbon isotope fractionation, but inter-specimen differences suggested that physiological factors exert systematic control on δ13C values inHyriopsis. Results also suggest that if the annual mean δ13CDICvalue is to be inferred for a fluvial system from shell δ13C values, multiple specimens should be sampled, and the annual mean value yields a temporally integrated measure of the stable isotopic composition of the river system. Given the carbon isotope fractionation between ambient DIC and shell is +2.0 ± 0.7 ‰ (2 se), we estimated thatpCO2averaged ~6,850 μatm during shell growth periods from 2002 to 2007. ThepCO2concentration was an order of magnitude greater than the atmospheric equilibrium value in all years, suggesting that CO2was lost from surface water to the atmosphere or downstream to the lake. These losses must be accounted for when considering the regional redistribution of CO2. Our results extend the utility of δ13C measures in freshwater bivalves for inferring the δ13CDIChistory of ambient waters. This tool provides information that is complementary to that gained from direct δ13CDICmeasurement and should enable inference of long-term changes in critical variables such aspCO2.