In coastal regions, rivers and streams may be important sources of nutrients limiting to primary production in marine waters; however, sampling is still rarely conducted across the land-to-ocean aquatic continuum, precluding conclusions from being drawn about connectivity between freshwater and marine systems. Here we use a more-than-4-year dataset (2014–2018) of nutrients (nitrogen, phosphorus, silica, iron) and dissolved organic carbon spanning streams draining coastal watersheds and nearshore marine surface waters along the Central Coast of British Columbia, Canada, at the heart of the North Pacific coastal temperate rainforest region. Mean freshwater and surface marine $\mathrm{N}:\mathrm{Si}:\mathrm{P}$ ratios were $\mathrm{5}:\mathrm{20}:\mathrm{1}$ (P:Fe = 1:67) and $\mathrm{6}:\mathrm{11}:\mathrm{1}$, respectively, showing relative consistency across the land–ocean interface but deviation from the extended Redfield ratio. Inorganic nutrient concentrations (${\mathrm{NO}}_{\mathrm{3}}^{-}+{\mathrm{NO}}_{\mathrm{2}}^{-}$, ${\mathrm{PO}}_{\mathrm{4}}^{\mathrm{3}-}$, Si(OH)₄) in fresh waters were less than in the receiving marine environment, indicating that freshwater nutrient inputs in this region were of little importance to – or even diluted – the pool of readily available inorganic nutrients in nearshore waters. Conversely, fresh waters increased the pool of organic-matter-associated nutrients, namely dissolved organic nitrogen and iron. The organic-matter-rich landscapes of the region yielded globally significant quantities of dissolved organic nitrogen (304–381 kg km⁻² yr⁻¹) and iron (463–596 kg km⁻² yr⁻¹), thus acting as important sources of potentially limiting nutrients to both nearshore and offshore waters. These exports may subsidise heterotrophic microbial communities capable of directly consuming and remineralising these nutrients, potentially compensating for the dilution of inorganic nutrients by freshwater inputs. We highlight the need to better understand nutrient limitation in coastal waters and for concerted research efforts to study the spatial and temporal dynamism at the land–ocean interface along the northeast Pacific coast.

中文翻译：

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雨水喂养的溪流稀释了无机养分，但补贴了东北太平洋沿海水域的有机物相关养分

在沿海地区，河流和溪流可能是重要的养分来源，限制了海水的初级生产；但是，仍然很少在陆地到海洋的水生连续性区域进行采样，从而排除了从淡水和海洋系统之间的连通性得出的结论。在这里，我们使用了超过4年（2014-2018年）的数据集（氮，磷，二氧化硅，铁）和溶解的有机碳，这些数据跨越不列颠哥伦比亚省中部海岸沿岸集水区和近岸海洋地表水流失，加拿大位于北太平洋沿海温带雨林地区的中心。平均淡水和地表海洋$\mathrm{ñ}：\mathrm{硅}：\mathrm{P}$ 比率是 $\mathrm{5}：\mathrm{20}：\mathrm{1个}$（P：Fe  =  1:67）和$\mathrm{6}：\mathrm{11}：\mathrm{1个}$分别显示了陆地-海洋界面的相对一致性，但偏离了扩展的雷德菲尔德比。无机养分浓度（${\mathrm{不}}_{\mathrm{3}}^{--}+{\mathrm{不}}_{\mathrm{2个}}^{--}$， ${\mathrm{采购订单}}_{\mathrm{4}}^{\mathrm{3}--}$，淡水中的Si（OH ）₄）少于接收海洋环境中的水，这表明该区域的淡水养分输入对近岸水域中随时可用的无机养分池并不重要，甚至被稀释。相反，淡水增加了与有机物相关的养分，即溶解的有机氮和铁。该地区富含有机物的景观在全球范围内产生大量的溶解有机氮（304-381 kg km ^-2  yr ^-1）和铁（463-596 kg km ^-2  yr ^-1）），因此可能成为限制近岸和近岸水域养分的重要来源。这些出口可能补贴能够直接消耗和再矿化这些养分的异养微生物群落，从而可能补偿淡水输入对无机养分的稀释作用。我们强调需要更好地了解沿海水域中的养分限制，并需要开展协调的研究工作来研究东北太平洋沿岸海陆交界处的时空动态。