Savoie Allison M, Moody Amy, Gilbert Melissa, Dillon Kevin S, Howden Stephan D, Shiller Alan M, Hayes Christopher T
Department of Oceanography Texas A&M University College Station Texas.
School of Ocean Science and Engineering University of Southern Mississippi Stennis Space Center Mississippi.
Limnol Oceanogr. 2022 Dec;67(12):2779-2795. doi: 10.1002/lno.12237. Epub 2022 Oct 10.
Coastal ecosystems are highly dynamic areas for carbon cycling and are likely to be negatively impacted by increasing ocean acidification. This research focused on dissolved inorganic carbon (DIC) and total alkalinity (TA) in the Mississippi Sound to understand the influence of local rivers on coastal acidification. This area receives large fluxes of freshwater from local rivers, in addition to episodic inputs from the Mississippi River through a human-built diversion, the Bonnet Carré Spillway. Sites in the Sound were sampled monthly from August 2018 to November 2019 and weekly from June to August 2019 in response to an extended spillway opening. Prior to the 2019 spillway opening, the contribution of the local, lower alkalinity rivers to the Sound may have left the study area more susceptible to coastal acidification during winter months, with aragonite saturation states (Ω) < 2. After the spillway opened, despite a large increase in TA throughout the Sound, aragonite saturation states remained low, likely due to hypoxia and increased CO concentrations in subsurface waters. Increased Mississippi River input could represent a new normal in the Sound's hydrography during spring and summer months. The spillway has been utilized more frequently over the last two decades due to increasing precipitation in the Mississippi River watershed, which is primarily associated with climate change. Future increases in freshwater discharge and the associated declines in salinity, dissolved oxygen, and Ω in the Sound will likely be detrimental to oyster stocks and the resilience of similar ecosystems to coastal acidification.
沿海生态系统是碳循环高度活跃的区域，很可能受到海洋酸化加剧的负面影响。本研究聚焦于密西西比湾的溶解无机碳（DIC）和总碱度（TA），以了解当地河流对沿海酸化的影响。该区域除了通过人工建造的分洪道邦尼特卡里分洪道偶尔接收来自密西西比河的水之外，还接收来自当地河流的大量淡水。为响应分洪道延长开放，于2018年8月至2019年11月每月对海湾中的站点进行采样，并于2019年6月至8月每周采样一次。在2019年分洪道开放之前，当地碱度较低的河流对海湾的贡献可能使研究区域在冬季更容易受到沿海酸化的影响，文石饱和度（Ω）<2。分洪道开放后，尽管整个海湾的TA大幅增加，但文石饱和度仍然很低，这可能是由于缺氧以及次表层水中CO浓度增加所致。密西西比河输入量的增加可能代表了海湾春季和夏季水文状况的新常态。在过去二十年中，由于密西西比河流域降水量增加（这主要与气候变化有关），分洪道的使用频率更高。未来淡水排放量的增加以及随之而来的海湾盐度、溶解氧和Ω的下降可能会对牡蛎种群以及类似生态系统对沿海酸化的恢复力产生不利影响。
