Characteristics of the Carbonate System in a Semiarid Estuary that Experiences Summertime Hypoxia
Characteristics of the Carbonate System in a Semiarid Estuary that Experiences Summertime Hypoxia
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DOI：
10.1007/s12237-019-00588-0
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发表时间：
2019-06
影响因子：
2.7
通讯作者：
Melissa R. McCutcheon;Cory J. Staryk;Xinping Hu
中科院分区：
文献类型：
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作者：
Melissa R. McCutcheon;Cory J. Staryk;Xinping Hu
在海洋环境中，已经发现两种CO2源有助于分层水体的酸化，即，人为增加大气CO2和呼吸产生的有机质矿化CO2的CO2入侵。从开放的大陆架到封闭的河口，在许多环境中经常观察到由这些CO2源引起的酸化。在这里，我们报告的观测碳酸盐系统的动态在一个相对良好的缓冲泻湖河口，科珀斯克里斯蒂湾（CCB），在半干旱的亚热带地区，夏季缺氧以及强烈的蒸发和海草植被附近的影响。虽然溶解氧（DO）和pH值之间的关系在底部沃茨的CCB是积极的，在其他沿海和河口环境中容易缺氧，斜率显着小于在其他系统。我们认为CCB的高缓冲能力是由于CCB附近存在丰富的海草草甸，以及将低CO2水输送到CCB底部的强蒸发产生的密度流。因此，尽管出现缺氧，但底层水碳酸盐相对于文石的饱和状态（Ωarg）和CO2分压（pCO2）都没有达到临界水平，即，不饱和（即，Ωarag<1）或高碳酸血症（pCO2>1000 µatm）。
In oceanic environments, two sources of CO2have been found to contribute to acidification of stratified water bodies, i.e., CO2invasion due to anthropogenic atmospheric CO2increase and respiration-produced CO2from organic matter remineralization. Acidification caused by these CO2sources has been observed frequently in numerous environments spanning from open continental shelves to enclosed estuaries. Here, we report observations on carbonate system dynamics in a relatively well-buffered lagoonal estuary, Corpus Christi Bay (CCB), in a semiarid subtropical region that is influenced by summertime hypoxia as well as strong evaporation and seagrass vegetation in the vicinity. While the relationship between dissolved oxygen (DO) and pH in the bottom waters of CCB was positive as in other coastal and estuarine environments prone to hypoxia, the slope was significantly less than in other systems. We attribute the high buffering capacity in CCB to the presence of abundant seagrass meadows adjacent to CCB and strong evaporation-produced density flow that delivers low CO2waters to the bottom of CCB. Thus, despite the occurrence of hypoxia, neither bottom water carbonate saturation state with respect to aragonite (Ωarg) nor CO2partial pressure (pCO2) reached critical levels, i.e., undersaturation (i.e., Ωarag<1) or hypercapnia (pCO2>1000 µatm), respectively.