Western Ecology Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, United States Environmental Protection Agency, Newport, OR 97365;
College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331.
Proc Natl Acad Sci U S A. 2018 Apr 10;115(15):3870-3875. doi: 10.1073/pnas.1703445115. Epub 2018 Apr 2.
The role of rising atmospheric CO in modulating estuarine carbonate system dynamics remains poorly characterized, likely due to myriad processes driving the complex chemistry in these habitats. We reconstructed the full carbonate system of an estuarine seagrass habitat for a summer period of 2.5 months utilizing a combination of time-series observations and mechanistic modeling, and quantified the roles of aerobic metabolism, mixing, and gas exchange in the observed dynamics. The anthropogenic CO burden in the habitat was estimated for the years 1765-2100 to quantify changes in observed high-frequency carbonate chemistry dynamics. The addition of anthropogenic CO alters the thermodynamic buffer factors (e.g., the Revelle factor) of the carbonate system, decreasing the seagrass habitat's ability to buffer natural carbonate system fluctuations. As a result, the most harmful carbonate system indices for many estuarine organisms [minimum pH, minimum Ω, and maximum pCO] change up to 1.8×, 2.3×, and 1.5× more rapidly than the medians for each parameter, respectively. In this system, the relative benefits of the seagrass habitat in locally mitigating ocean acidification increase with the higher atmospheric CO levels predicted toward 2100. Presently, however, these mitigating effects are mixed due to intense diel cycling of CO driven by aerobic metabolism. This study provides estimates of how high-frequency pH, Ω, and pCO dynamics are altered by rising atmospheric CO in an estuarine habitat, and highlights nonlinear responses of coastal carbonate parameters to ocean acidification relevant for water quality management.
大气中 CO 上升在调节河口碳酸盐系统动力学方面的作用仍未得到很好的描述，这可能是由于众多过程驱动了这些生境的复杂化学过程。我们利用时间序列观测和机制模型，对一个河口海草生境的整个碳酸盐系统进行了重建，重建时间为 2.5 个月的夏季，并量化了好氧代谢、混合和气体交换在观测到的动力学中的作用。估计了该生境中人为 CO 的负担，以便量化 1765 年至 2100 年观测到的高频碳酸盐化学动力学变化。人为 CO 的增加改变了碳酸盐系统的热力学缓冲因子（例如，雷维尔因子），降低了海草生境缓冲自然碳酸盐系统波动的能力。结果，许多河口生物的最有害的碳酸盐系统指数[最小 pH 值、最小 Ω 值和最大 pCO 值]的变化速度比每个参数的中位数快高达 1.8×、2.3×和 1.5×。在这个系统中，海草生境在局部缓解海洋酸化方面的相对益处随着 2100 年大气中 CO 水平的升高而增加。然而，目前由于好氧代谢驱动的 CO 的强烈昼夜循环，这些缓解效应是混合的。本研究提供了大气中 CO 升高如何改变河口生境中高频 pH 值、Ω 值和 pCO 值的估计值，并强调了沿海碳酸盐参数对海洋酸化的非线性响应，这对于水质管理很重要。
