To use elements as salinity proxies, relationships of elemental concentrations with salinity must be known and vary from freshwater to marine endmembers. To extend these proxies to biogenic carbonates, elements must incorporate into carbonate matrices proportional to environmental concentrations. Therefore, this study quantified calcium (Ca), magnesium (Mg), strontium (Sr), barium (Ba), and manganese (Mn) in Mobile Bay, Alabama from freshwater to marine endmembers. Two smaller drainages (Fowl River and Dog River) were quantified to determine if all freshwater elemental concentrations were consistent. The ratio of elements (Mg, Sr, Ba, Mn) to Ca were also measured in water and Red Drum otolith edges across the salinity gradient. Water Ca, Sr, and Mg had positive relationships with salinity, but Ca and Sr were lower in Fowl River freshwater. Barium exhibited a mid-salinity peak and decreased with further salinity increases. More Ba and Mn were present during low river discharge; however, Mn did not vary with salinity. In both water and otoliths, Sr:Ca increased and Ba:Ca decreased non-linearly with salinity increases, Mn:Ca exhibited no relationship with salinity, and Mg:Ca increased non-linearly in water. These results demonstrate that Sr:Ca and Ba:Ca may be used as salinity proxies within the Mobile Bay estuary and likely other estuaries in the region. However, given non-linearity of element:Ca salinity relationships, variable concentrations among species and estuaries from other studies, and variation in elemental ratios between drainages and flow regimes, species-specific element salinity relationships should be known in the estuary of interest prior to utilizing elemental salinity proxies.

中文翻译：

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墨西哥湾北部河口作为盐度替代物的水和耳石的元素浓度

要将元素用作盐度代理，必须知道元素浓度与盐度的关系，并且从淡水到海洋最终成员都各不相同。为了将这些代理扩展到生物碳酸盐，元素必须与环境浓度成比例地掺入碳酸盐基质中。因此，本研究对阿拉巴马州莫比尔湾从淡水到海洋最终成员的钙（Ca），镁（Mg），锶（Sr），钡（Ba）和锰（Mn）进行了定量。对两个较小的排水系统（福尔河和狗河）进行了量化，以确定所有淡水元素浓度是否一致。还测量了整个盐度梯度中水和红鼓耳石边缘中元素（镁，锶，钡，锰）与钙的比例。水Ca，Sr和Mg与盐度呈正相关，而Fowl River淡水中的Ca和Sr较低。钡显示出一个中盐度峰值，并随着盐度的进一步增加而降低。低河流量时存在更多的钡和锰。但是，Mn不随盐度变化。在水和耳石中，Sr：Ca和Ba：Ca随盐度的增加呈非线性关系，Mn：Ca与盐度没有关系，Mg：Ca在水中呈非线性关系。这些结果表明，Sr：Ca和Ba：Ca可用作莫比尔湾河口以及该地区其他河口内的盐度代理。但是，考虑到元素：Ca盐度关系的非线性，其他研究中物种和河口之间的浓度变化以及排水和流态之间的元素比变化，