Biogeochemical processes and buffering capacity concurrently affect acidification in a seasonally hypoxic coastal marine basin
Biogeochemical processes and buffering capacity concurrently affect acidification in a seasonally hypoxic coastal marine basin
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DOI：
10.5194/bg-12-1561-2015
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发表时间：
2015-01-01
期刊：
影响因子：
4.9
通讯作者：
Middelburg, J. J.
中科院分区：
文献类型：
--
作者：
Hagens, M.;Slomp, C. P.;Middelburg, J. J.
沿海地区受到多种自然和人为过程的影响，其pH值波动比公海更大。这些变化可以减弱或加强由大气pCO增加引起的海洋酸化信号。富营养化引起的缺氧的发展加剧了沿海酸化，因为呼吸过程中产生的CO2降低了任何缺氧底层水的缓冲能力。为了评估酸化和缺氧对生态系统的综合影响，我们量化了季节性分层的沿海盆地水体中pH值和氧动力学的季节性变化（荷兰Grevelingen湖）。每月水柱化学测量补充了使用O-2光暗孵育的初级生产和呼吸估计，此外，沉积物-水通量的溶解无机碳（DIC）和总碱度（TA）。由此产生的数据集被用来建立一个质子预算的季节scale. Temperature引起的季节分层相结合的高社区呼吸是负责在夏季的底层水中的氧气耗尽。地表水表现出强烈的季节性变化的过程速率（初级生产，CO2海气交换），但相对较小的季节性pH值波动（0.46单位的总氢离子规模）。与此相反，底层水表现出较少的季节性在地球化学速率（呼吸作用，沉积物-水交换），但较强的pH值波动（0.60单位）。这种显着的差异，pH值动态可归因于在夏季缺氧的底层水的酸碱缓冲能力的大幅减少。我们的研究结果强调了酸碱缓冲在沿海系统的pH动态的重要性，并说明了日益脆弱的缺氧，富含二氧化碳的沃茨任何酸化过程。
Coastal areas are impacted by multiple natural and anthropogenic processes and experience stronger pH fluctuations than the open ocean. These variations can weaken or intensify the ocean acidification signal induced by increasing atmospheric pCO(2). The development of eutrophication-induced hypoxia intensifies coastal acidification, since the CO2 produced during respiration decreases the buffering capacity in any hypoxic bottom water. To assess the combined ecosystem impacts of acidification and hypoxia, we quantified the seasonal variation in pH and oxygen dynamics in the water column of a seasonally stratified coastal basin (Lake Grevelingen, the Netherlands).Monthly water-column chemistry measurements were complemented with estimates of primary production and respiration using O-2 light-dark incubations, in addition to sediment-water fluxes of dissolved inorganic carbon (DIC) and total alkalinity (TA). The resulting data set was used to set up a proton budget on a seasonal scale.Temperature-induced seasonal stratification combined with a high community respiration was responsible for the depletion of oxygen in the bottom water in summer. The surface water showed strong seasonal variation in process rates (primary production, CO2 air-sea exchange), but relatively small seasonal pH fluctuations (0.46 units on the total hydrogen ion scale). In contrast, the bottom water showed less seasonality in biogeochemical rates (respiration, sediment-water exchange), but stronger pH fluctuations (0.60 units). This marked difference in pH dynamics could be attributed to a substantial reduction in the acid-base buffering capacity of the hypoxic bottom water in the summer period. Our results highlight the importance of acid-base buffering in the pH dynamics of coastal systems and illustrate the increasing vulnerability of hypoxic, CO2-rich waters to any acidifying process.