The coastal ocean is strongly affected by ocean acidification because of its shallow water depths, low volume, and the closeness to terrestrial dynamics. Earlier observations of dissolved inorganic carbon (DIC) and total alkalinity (TA) in the southern part of the North Sea, a northwest European shelf sea, revealed lower acidification effects than expected. It has been assumed that anaerobic degradation and subsequent TA release in the adjacent back-barrier tidal areas (Wadden Sea) in summertime is responsible for this phenomenon. In this study the exchange rates of TA and DIC between the Wadden Sea tidal basins and the North Sea and the consequences for the carbonate system in the German Bight are estimated using a 3D ecosystem model. The aim of this study is to differentiate the various sources contributing to observed high summer TA in the southern North Sea. Measured TA and DIC in the Wadden Sea are considered as model boundary conditions. This procedure acknowledges the dynamic behaviour of the Wadden Sea as an area of effective production and decomposition of organic material. According to the modelling results, 39 Gmol TA yr⁻¹ were exported from the Wadden Sea into the North Sea, which is less than a previous estimate but within a comparable range. The interannual variabilities in TA and DIC, mainly driven by hydrodynamic conditions, were examined for the years 2001–2009. Dynamics in the carbonate system are found to be related to specific weather conditions. The results suggest that the Wadden Sea is an important driver for the carbonate system in the southern North Sea. On average 41 % of TA inventory changes in the German Bight were caused by riverine input, 37 % by net transport from adjacent North Sea sectors, 16 % by Wadden Sea export, and 6 % were caused by internal net production of TA. The dominant role of river input for the TA inventory disappears when focusing on TA concentration changes due to the corresponding freshwater fluxes diluting the marine TA concentrations. The ratio of exported TA versus DIC reflects the dominant underlying biogeochemical processes in the Wadden Sea. Whereas aerobic degradation of organic matter played a key role in the North Frisian Wadden Sea during all seasons of the year, anaerobic degradation of organic matter dominated in the East Frisian Wadden Sea. Despite the scarcity of high-resolution field data, it is shown that anaerobic degradation in the Wadden Sea is one of the main contributors of elevated summer TA values in the southern North Sea.

中文翻译：

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潮间带对北海南部碳酸盐体系的影响

沿海海洋由于其浅水深度，体积小和接近陆地动力学而受到海洋酸化的强烈影响。早先在西北海陆架海北海南部溶解的无机碳（DIC）和总碱度（TA）的观测表明，酸化作用低于预期。有人认为，夏季这种现象是由于邻近的后屏障潮汐区（瓦登海）的厌氧降解和随后的TA释放引起的。在这项研究中，瓦登海潮汐盆地和北海之间的TA和DIC交换率以及德国海岸线上碳酸盐系统的后果是使用3D生态系统模型估算的。这项研究的目的是区分造成北海南部夏季高温TA的各种来源。瓦登海中测得的TA和DIC被视为模型边界条件。该程序承认瓦登海的动态行为是有效生产和分解有机材料的区域。根据建模结果，39 Gmol TA yr^-1是从瓦登海出口到北海的，比先前的估计要少，但在可比范围内。在2001-2009年期间，研究了主要由流体动力条件驱动的TA和DIC的年际变化。发现碳酸盐体系中的动力学与特定的天气条件有关。结果表明，瓦登海是北海南部碳酸盐体系的重要驱动力。平均而言，德国沿海地区的技术援助库存变化中，有41％是由河流投入造成的，来自北海相邻地区的净运输占37％，瓦登海出口构成的是16％，内部有技术援助则是6％。当关注TA浓度变化时，由于相应的淡水通量稀释了海洋TA浓度，河流输入对于TA清单的主导作用消失了。出口的TA与DIC之比反映了瓦登海主要的潜在生物地球化学过程。在一年中的所有季节中，有机物的需氧降解在北弗里斯兰沃登海中都起着关键作用，而东弗里斯兰州的沃登海有机质的厌氧降解则占主导地位。尽管缺乏高分辨率的现场数据，但表明瓦登海的厌氧降解是北海南部夏季TA值升高的主要因素之一。在一年中的所有季节中，有机物的需氧降解在北弗里斯兰沃登海中都起着关键作用，而东弗里斯兰州的沃登海有机质的厌氧降解则占主导地位。尽管缺乏高分辨率的现场数据，但表明瓦登海的厌氧降解是北海南部夏季TA值升高的主要因素之一。在一年中的所有季节中，有机物的需氧降解在北弗里斯兰沃登海中都起着关键作用，而东弗里斯兰州的沃登海有机质的厌氧降解则占主导地位。尽管缺乏高分辨率的现场数据，但表明瓦登海的厌氧降解是北海南部夏季TA值升高的主要因素之一。