Estuaries are essential drivers of primary productivity in coastal waters through the export of dissolved and suspended material. This study aims at quantifying this fertilization process at the two main estuaries in South Portugal, where typical low river discharge conditions occur in winter due to strong flow regulation by upstream dams and seldom-local rain events. Data were collected across the channel of the lower Arade (10/01/2018) and Guadiana (04/02/2019) estuaries during a semi-diurnal tidal cycle with intermediate tidal ranges (1.5 m and 2.2 m, respectively). Current velocity records were completed with hourly water quality measurements (temperature, salinity, pH, dissolved oxygen, suspended solids, chlorophyll a and nutrients) for determination of the along channel fluxes and residual mass transport of dissolved and suspended matter across the channel sections. The results show that the two estuaries were characterized by distinct water circulation patterns and tidal properties (e.g., standing wave at the Arade, mixed wave at the Guadiana). The concentration of dissolved and particulate matter displayed a general similar anti-phase pattern of variations with tidal height at both sites. The corresponding fluxes were generally strongest during the ebb phase. Thus, the residual mass transport was seaward, indicating that both estuaries contribute to fertilize adjacent coastal waters by exporting nutrients (order of kg), chlorophyll a (order of kg) and suspended solids (up to tons). Moreover, transport differences at both estuaries reflect specific discharge flow and environmental conditions as well as contamination sources close to the study areas. In particular, the signatures of a discharge event from a water treatment plant at the Arade and of coastal upwelling at the Guadiana were identified.

通过出口溶解和悬浮物质，河口是沿海水域初级生产力的重要驱动力。这项研究旨在量化南葡萄牙的两个主要河口的施肥过程，由于上游大坝对水流的强力调节以及很少发生局部降雨事件，冬季典型的低河流量发生在冬季。在半潮汐周期和中间潮差范围内（分别为1.5 m和2.2 m），在较低的Arade（10/01/2018）和Guadiana（04/02/2019）河口通道收集数据。通过每小时的水质测量（温度，盐度，pH，溶解氧，悬浮固体，叶绿素a）完成当前速度记录和营养物）以确定沿通道的通量以及溶解和悬浮的物质在通道段中的残留质量传输。结果表明，这两个河口的特征是明显的水循环模式和潮汐特性（例如Arade处的驻波，Guadiana处的混合波）。溶解物和颗粒物的浓度在两个位置都显示出与潮汐高度变化大致相似的反相模式。相应的通量通常在退潮阶段最强。因此，残余的大量运输是向海的，这表明两个河口都通过输出养分（千克量），叶绿素a来为邻近的沿海水域施肥。（公斤级）和悬浮固体（不超过吨）。此外，两个河口的运输差异反映了特定的排放流量和环境条件以及研究区域附近的污染源。特别是，确定了Arade的水处理厂的排放事件和Guadiana的沿海上升流的特征。