Coastal waters have strong gradients in dissolved organic matter (DOM) quantity and characteristics, originating from terrestrial inputs and autochthonous production. Enclosed seas with high freshwater input therefore experience high DOM concentrations and gradients from freshwater sources to more saline waters. The brackish Baltic Sea experiences such salinity gradients from east to west and from river mouths to the open sea. Furthermore, the catchment areas of the Baltic Sea are very diverse and vary from sparsely populated northern areas to densely populated southern zones. Coastal systems vary from enclosed or open bays, estuaries, fjords, archipelagos and lagoons where the residence time of DOM at these sites varies and may control the extent to which organic matter is biologically, chemically or physically modified or simply diluted with transport off-shore. Data of DOM with simultaneous measurements of dissolved organic (DO) nitrogen (N), carbon (C) and phosphorus (P) across a range of contrasting coastal systems are scarce. Here we present data from the Roskilde Fjord, Vistula and Öre estuaries and Curonian Lagoon; four coastal systems with large differences in salinity, nutrient concentrations, freshwater inflow and catchment characteristics. The C:N:P ratios of DOM of our data, despite high variability, show site specific significant differences resulting largely from differences residence time. Microbial processes seemed to have minor effects, and only in spring did uptake of DON in the Vistula and Öre estuaries take place and not at the other sites or seasons. Resuspension from sediments impacts bottom waters and the entire shallow water column in the Curonian Lagoon. Finally, our data combined with published data show that land use in the catchments seems to impact the DOC:DON and DOC:DOP ratios of the tributaries most.

中文翻译：

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四个浅波罗的海河口溶解有机物的起源和归宿

沿海水域的溶解有机质 (DOM) 数量和特征具有很强的梯度，源自陆地输入和本土生产。因此，淡水输入量高的封闭海域会经历高 DOM 浓度和从淡水源到更多咸水的梯度。咸咸的波罗的海从东到西，从河口到公海经历了这样的盐度梯度。此外，波罗的海的集水区非常多样化，从人口稀少的北部地区到人口稠密的南部地区不等。沿海系统不同于封闭或开放的海湾、河口、峡湾、群岛和泻湖，它们在这些地点的 DOM 的停留时间各不相同，并且可能控制有机物的生物程度，化学或物理改性或简单地通过离岸运输稀释。在一系列对比鲜明的沿海系统中同时测量溶解有机物 (DO) 氮 (N)、碳 (C) 和磷 (P) 的 DOM 数据很少。在这里，我们展示了罗斯基勒峡湾、维斯杜拉河和厄勒河口以及库尔斯泻湖的数据；四个沿海系统在盐度、养分浓度、淡水流入量和流域特征方面差异很大。我们数据的 DOM 的 C:N:P 比率，尽管变异性很大，但显示出站点特定的显着差异，这主要是由于停留时间不同造成的。微生物过程的影响似乎很小，只有在春季，维斯杜拉河和厄勒河口才会吸收 DON，而在其他地点或季节则没有。沉积物的再悬浮影响库尔斯泻湖的底水和整个浅水柱。最后，我们的数据与公布的数据相结合表明，流域的土地利用似乎对支流的 DOC:DON 和 DOC:DOP 比率影响最大。