Small mountainous coastal basins display steeper gradients, suggesting intensified river transport. However, there is little information about downstream trends in rivers with low discharge and material fluxes across coastal plains and its influence on land‐sea material transport. This study examined 2 years of river discharge, suspended sediment and nutrient concentrations, fluxes and yields from upstream to the upper estuary of a typical South‐east Atlantic Basin. This study provides data about the material retention capacity of the coastal plain. The results indicated that the coastal plain did not affect nutrient concentrations, but reduced turbidity, inducing chlorophyll a and consequently primary productivity in the lower river basin and upper estuary. The coastal plain attenuated the increasing downstream material fluxes, but also curbed suspended sediment and TN fluxes, across the lower river/upper estuary. In contrast, TP and PO₄³⁻ fluxes increased sharply across the coastal plain. This was influenced by natural and anthropogenic P inputs from soils and run‐off to the river channel. These exceeded the retention capacity of the coastal plain and result in a high export efficiency of this nutrient to the sea.

中文翻译：

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沿海平原对沿海小山区河流流域下游物质通量的影响

山区多山沿海盆地显示出更陡峭的坡度，表明河流运输加剧。但是，关于低流量和跨沿海平原物质通量的河流下游趋势及其对陆海物质运输的影响的信息很少。这项研究调查了典型东南大西洋盆地从上游到上河口的2年河流流量，悬浮沉积物和养分浓度，通量和产量。这项研究提供了有关沿海平原物质保留能力的数据。结果表明，沿海平原不影响养分含量，但降低浊度，诱导叶绿素a从而导致下游流域和上游河口的初级生产力。沿海平原减弱了下游河床/河口上游增加的下游物质通量，但也抑制了悬浮的泥沙和总氮通量。相反，整个沿海平原的TP和PO ₄ ^3-通量急剧增加。这是受到土壤和人为的自然磷输入以及径流到河道的影响。这些超出了沿海平原的保留能力，导致这种养分向海洋的高出口效率。