Aragonite saturation states in estuaries along a climate gradient in the northwestern Gulf of Mexico
Aragonite saturation states in estuaries along a climate gradient in the northwestern Gulf of Mexico
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DOI：
10.3389/fenvs.2022.951256
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发表时间：
2022-10
期刊：
影响因子：
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通讯作者：
Xinping Hu;H. Yao;Melissa R. McCutcheon;L. Dias;Cory J. Staryk;M. Wetz;P. Montagna
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文献类型：
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作者：
Xinping Hu;H. Yao;Melissa R. McCutcheon;L. Dias;Cory J. Staryk;M. Wetz;P. Montagna
在墨西哥湾西北部（nwGOM），沿海气候突然从潮湿的东北部转变为半干旱的西南部在一个狭窄的纬度范围内。气候效应在控制淡水入河口的过程中起着重要作用。除了减少沿海岸的淡水径流外，蒸发也大幅增加。因此，由于淡水流入平衡（河流径流和降水减去蒸发和转移）的巨大差异，这些河口显示出沿着海岸线的盐度增加。然而，这种空间梯度可以被强烈的风暴事件破坏，因为大量的降水会导致河流泛滥，在极端情况下，除了淡水引起的短暂分层外，还会导致这些系统的暂时清新。我们检查了2014年至2018年收集的河口水文石饱和状态（Ωarag）数据，涵盖了从最初的干旱到多次洪水事件的对比水文条件，包括受4级飓风影响的短暂时期。根据淡水供应情况，这些河口从淡水最丰富的瓜达尔卡巴纳河口到淡水最匮乏的努埃西斯河口，Ωarag波动逐渐减小。虽然Ωarag值通常远高于阈值水平（Ωarag = 1），但短暂的淡水排放事件和随后较低水柱中的低氧水平导致了间歇性腐蚀条件。基于先前获得的Ωarag时间趋势和本研究中获得的Ωarag值，我们估计了Ωarag的出现时间（ToE）。不仅河口显示出随着淡水供应的减少而减少的ToE，而且淡水影响较小的各个河口的子海湾也具有较短的ToE。这种空间格局表明，规划沿海恢复工作，特别是贝类生物，应强调具有较长的脚趾的地区。
In the northwestern Gulf of Mexico (nwGOM), the coastal climate shifts abruptly from the humid northeast to the semiarid southwest within a narrow latitudinal range. The climate effect plays an important role in controlling freshwater discharge into the shallow estuaries in this region. In addition to diminishing freshwater runoff down the coast, evaporation also increases substantially. Hence, these estuaries show increasing salinity along the coastline due to the large difference in freshwater inflow balance (river runoff and precipitation minus evaporation and diversion). However, this spatial gradient can be disrupted by intense storm events as a copious amount of precipitation leads to river flooding, which can cause temporary freshening of these systems in extreme cases, in addition to freshwater-induced ephemeral stratification. We examined estuarine water aragonite saturation state (Ωarag) data collected between 2014 and 2018, covering a period of contrasting hydrological conditions, from the initial drought to multiple flooding events, including a brief period that was influenced by a category 4 hurricane. Based on freshwater availability, these estuaries exhibited a diminishing Ωarag fluctuation from the most freshwater enriched Guadalupe Estuary to the most freshwater-starved Nueces Estuary. While Ωarag values were usually much higher than the threshold level (Ωarag = 1), brief freshwater discharge events and subsequent low oxygen levels in the lower water column led to episodic corrosive conditions. Based on previously obtained Ωarag temporal trends and Ωarag values obtained in this study, we estimated the time of emergence (ToE) for Ωarag. Not only did estuaries show decreasing ToE with diminishing freshwater availability but the sub-embayments of individual estuaries that had a less freshwater influence also had shorter ToE. This spatial pattern suggests that planning coastal restoration efforts, especially for shellfish organisms, should emphasize areas with longer ToE.