Deciphering the dynamics of inorganic carbon export from intertidal salt marshes using high-frequency measurements
Deciphering the dynamics of inorganic carbon export from intertidal salt marshes using high-frequency measurements
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DOI：
10.1016/j.marchem.2018.08.005
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发表时间：
2018-10
期刊：
影响因子：
3
通讯作者：
Sophie N. Chu;Zhaohui Aleck Wang;M. Gonneea;K. Kroeger;N. Ganju
中科院分区：
文献类型：
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作者：
Sophie N. Chu;Zhaohui Aleck Wang;M. Gonneea;K. Kroeger;N. Ganju
海岸沼泽湿地碳交换的横向输出是沼泽湿地碳收支和海岸碳循环的重要组成部分。然而，由于复杂的潮汐动力学和碳的季节性循环，这种出口的规模很难准确量化。在这项研究中，我们usein原位，高频测量溶解无机碳（DIC）和水通量，以估计横向DIC通量从美国东北盐沼。DIC是由一个通道化的光学传感器（CHANOS），提供了一个原位浓度测量在15分钟的时间间隔，在夏季（7月至8月）和深秋（12月）。季节性变化的沼泽DIC浓度有很强的影响，而潮汐驱动的水通量的沼泽碳输出的基本车辆。间歇性事件，如地下水排放和平均海水水位变化，可以通过改变DIC浓度和水流来影响DIC通量。每个季节内的个别潮汐之间的变异性是可比的两个季节之间的平均变异性。DIC浓度和高频水通量的多元线性回归（MLR）模型的基础上估计的平均DIC通量同意合理以及来自CHANOS DIC测量两个研究期间，表明高频，模拟DIC浓度，加上连续的水通量测量和水动力学模型，提供了一个强大的DIC通量估计。此外，采样策略的分析表明，DIC通量计算使用传统的采样频率（每小时至每两小时）的一个单一的潮汐周期是不太可能捕获一个代表性的平均DIC通量相比，长期测量跨多个潮汐周期的采样频率在几十分钟的顺序。这是由于在少数潮汐周期中出现了不成比例的大量净DIC通量，而大多数潮汐的DIC输出接近于零。因此，在感兴趣的时间段内的高频测量（在几十分钟或更好的顺序）是必要的，以准确地量化从盐沼的碳物种的潮汐出口。
The lateral export of carbon from coastal marshesviatidal exchange is a key component of the marsh carbon budget and coastal carbon cycles. However, the magnitude of this export has been difficult to accurately quantify due to complex tidal dynamics and seasonal cycling of carbon. In this study, we usein situ, high-frequency measurements of dissolved inorganic carbon (DIC) and water fluxes to estimate lateral DIC fluxes from a U.S. northeastern salt marsh. DIC was measured by a CHANnelized Optical Sensor (CHANOS) that provided anin situconcentration measurement at 15-min intervals, during periods in summer (July – August) and late fall (December). Seasonal changes in the marsh had strong effects on DIC concentrations, while tidally-driven water fluxes were the fundamental vehicle of marsh carbon export. Episodic events, such as groundwater discharge and mean sea water level changes, can impact DIC flux through altered DIC concentrations and water flow. Variability between individual tides within each season was comparable to mean variability between the two seasons. Estimated mean DIC fluxes based on a multiple linear regression (MLR) model of DIC concentrations and high-frequency water fluxes agreed reasonably well with those derived from CHANOS DIC measurements for both study periods, indicating that high-frequency, modeled DIC concentrations, coupled with continuous water flux measurements and a hydrodynamic model, provide a robust estimate of DIC flux. Additionally, an analysis of sampling strategies revealed that DIC fluxes calculated using conventional sampling frequencies (hourly to two-hourly) of a single tidal cycle are unlikely to capture a representative mean DIC flux compared to longer-term measurements across multiple tidal cycles with sampling frequency on the order of tens of minutes. This results from a disproportionately large amount of the net DIC flux occurring over a small number of tidal cycles, while most tides have a near-zero DIC export. Thus, high-frequency measurements (on the order of tens of minutes or better) over the time period of interest are necessary to accurately quantify tidal exports of carbon species from salt marshes.