Spatial and Temporal Variability of Coastal Carbonate Chemistry in the Southern California Region
Spatial and Temporal Variability of Coastal Carbonate Chemistry in the Southern California Region
复制标题
南加州地区沿海碳酸盐化学的时空变化
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
Charlie Davidson
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文献类型：
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作者：
Charlie Davidson
本研究的目的是描述南加州近海岸无机碳化学的时空变异性。迄今为止，在近海岸环境（距离海岸<2英里）中进行的海水碳化学研究相对较少，本研究试图作为一个起点，以更好地了解该环境的当代条件和变化。在为期一年的时间里，每月在15个近岸地点收集海水样本，包括圣地亚哥地区的桑迪、岩石海滩和港口或海湾。这种方法的补充采样从船上沿着离岸运行样带在拉霍亚湾4个地点从表面到40米深。进行溶解无机碳（DIC）、总碱度（TA）、温度和盐度的测量。这些测量的参数被用来计算在原位pHSWS，文石饱和状态（[Ω]-文石），pCO_2，和空气-海洋CO_2通量在所有位置，如果适用。根据其局部环境，将样本位置分为三类：海滩/沙子、海滩/岩石和港口/海湾（图1）。在一般情况下，我们观察到大的空间和时间的变化DIC，TA，pHSWS，[欧米茄]-文石，pCO的，和CO的通量。最高的变异性，以及DIC和TA的最大值，发生在站分类为海湾/港口。分类为海滩/沙地和海滩/岩石的监测站变化较小，尽管与开阔海洋环境相比，它们仍然经历了较大的变化，在12个月的研究期间，DIC的平均值范围为±40 µmol kg至±100 µmol kg。值得注意的是，我们观察到一个整体的区域范围内减少TA，有助于降低海水pHSWS和[欧米茄]-文石在春季和夏季。计算出的pCO_2和CO_3通量表明，该地区作为一个源的CO_2的大气，结果是一致的，与以前的研究，这表明，内大陆架一般作为源的CO_2的大气。在一些监测站偶尔观察到低表层海水pH值和[Omega]-文石（有时分别低至7.51和1.0），显示出令人担忧的酸度水平，预计在下个世纪结束之前，公海不会出现这种情况。同样，沿海近海样带显示浅滩的低海水pH值和[欧米茄]-文石在春季和夏季，由于在这段时间内的上升流加剧。这些观测结果表明，沿海过程可能会加剧沿海海洋酸化的影响，对海水pH值和[欧米茄]-文石变化敏感的海洋生物产生潜在影响。总之，这项研究提供了关键数据，表明近岸环境是高度可变的，有时会遇到海水中的二氧化碳排放条件，预计在公海，直到很好的未来。它作为进一步研究的起点，旨在了解具有重大经济，生态，科学和社会重要性的近岸环境的复杂性
The objective of this study was to characterize temporal and spatial variability in near shore inorganic carbon chemistry in Southern California. To date, relatively little research has been conducted concerning seawater carbon chemistry in the near-shore environment (<2 miles from shore), and this study attempts to serve as a starting point to better understand the contemporary conditions and variability in this environment. Seawater samples were collected monthly for a one-year duration at 15 near-shore locations, encompassing sandy beaches, rocky beaches, and harbors or bays in the San Diego area. This approach was complemented by sampling from a boat along an offshore running transect in La Jolla Cove at 4 locations from the surface to 40m depth. Measurements of Dissolved Inorganic Carbon (DIC), Total Alkalinity (TA), Temperature, and Salinity were conducted. These measured parameters were used to calculate in situ pHSWS, aragonite saturation state ([Omega]-aragonite), pCO₂, and air-sea CO₂ flux at all locations where applicable. Sample locations were categorized, based on their localized environment, into three categories: beach/sand, beach/rock, and harbor/bay (Figure 1). In general, we observed large spatial and temporal variability in DIC, TA, pHSWS, [Omega]-aragonite, pCO₂, and CO₂ flux. The highest variability, as well as the largest values in DIC and TA, occurred in stations categorized as bay/harbor. Stations categorized as beach/ sand and beach/rock were less variable, although, compared to open ocean environments they still experienced large variability with averages of DIC ranging from ±40 µmol kg⁻¹ to ±100 µmol kg⁻¹ over the 12-month study period. Notably, we observed an overall region-wide decrease in TA that contributed to lower seawater pHSWS and [Omega]- aragonite during spring and summer. Calculated pCO₂ and CO₂ flux showed that the region acted as a source of CO₂ to the atmosphere, result that is consistent with previous studies, which have shown that inner continental shelves in general serve as sources of CO₂ to the atmosphere. Low surface seawater pH and [Omega]-aragonite were occasionally observed at some of the stations (sometimes as low as 7.51 and 1.0, respectively), showing a worrying level of acidity not expected in the open ocean until the end of the next century. Similarly, the coastal offshore transect revealed shoaling of low seawater pH and [Omega]- aragonite in the spring and summer as a result of intensified upwelling during this time period. These observations show how coastal processes are likely to intensify the effects of ocean acidification in the coastal ocean with potential consequences to marine organisms sensitive to changes in seawater pH and [Omega]- aragonite. In conclusion, this study provides key data showing that the near-shore environment is highly variable and on occasion experience seawater CO₂ conditions not expected in the open ocean until well into the future. It acts as starting point for further studies aiming to understand the complexity of the near-shore environments that is of major economic, ecologic, scientific, and social importance