We analysed the relationship between functional and structural variables (leaf litter decomposition, biofilms growth, primary productivity, invertebrate communities’ taxonomic structure, and biological traits) and environmental conditions from headwaters into the estuary, which remains under-investigated. Six river sections (headwaters, middle reach, and four large river sections with increasing salinity) and 18 sites were selected in the Mondego river (Central Portugal). Hypotheses of the expected variations were drawn, based on theory (e.g. River Continuum Concept—RCC) and previous studies. Abiotic conditions were strongly associated with macroinvertebrate communities’ taxonomic composition, but the relationship with functional parameters was different than the predicted one. Decomposition rates were similar from headwaters to the first large river sections (not expected) but increased in the estuarine sections. The high rates of decomposition were associated with the low salinity and especially with the high densities of the shredder Gammarus sp. Biofilm growth rate peaked in intermediate sections and was lower in the headwaters and in the estuary (not expected). The lower algae productivity in the estuary was not compensated by the heterotrophic component of the biofilm. The use of multiple biological traits indicated an unexpected higher functional similarity among the upper river sections, and differences within large river sections (not evident with taxonomic composition). These results show contradictions to widely accepted river concepts, such as the RCC, and highlight the importance of management practices adjusted to each river section to keep the ecosystem functioning. They also increased the knowledge on the transition zone between fresh and estuarine water which is important in the context of mitigation of climate change effects, considering the expected intrusion of saline water upstream.

我们分析了从上游到河口的功能和结构变量（叶凋落物分解，生物膜生长，初级生产力，无脊椎动物群落的分类结构和生物学特性）与环境条件之间的关系，目前该研究仍处于研究不足状态。在蒙德戈河（葡萄牙中部）选择了六个河段（上游水源，中游河段和四个盐度不断提高的大型河段）和18个站点。基于理论（例如河流连续体概念—RCC）和先前的研究，得出了预期变化的假设。非生物条件与大型无脊椎动物群落的分类组成密切相关，但与功能参数的关系与预测的条件不同。从源头到第一条大河段的分解速率相似（未预期），但在河口段分解速率增加。高分解率与低盐度有关，尤其与切碎机的高密度有关Gammarus sp。生物膜生长速率在中间部分达到峰值，而在源头和河口则较低（未预期）。河口较低的藻类生产力没有被生物膜的异养成分所补偿。多种生物学特性的使用表明上游河段之间意想不到的更高的功能相似性，以及大河段之间的差异（分类学组成不明显）。这些结果表明与广泛接受的河流概念（如RCC）相矛盾，并强调了针对每个河流段进行调整以保持生态系统功能的管理实践的重要性。他们还增加了对淡水和河口水过渡区的了解，这对于缓解气候变化影响非常重要，