Amazonian waters are classified into three biogeochemical categories by dissolved nutrient content, sediment type, transparency, and acidity—all important predictors of autochthonous and allochthonous primary production (PP): (1) nutrient-poor, low-sediment, high-transparency, humic-stained, acidic blackwaters; (2) nutrient-poor, low-sediment, high-transparency, neutral clearwaters; (3) nutrient-rich, low-transparency, alluvial sediment-laden, neutral whitewaters. The classification, first proposed by Alfred Russel Wallace in 1853, is well supported but its effects on fish are poorly understood. To investigate how Amazonian fish community composition and species richness are influenced by water type, we conducted quantitative year-round sampling of floodplain lake and river-margin habitats at a locality where all three water types co-occur. We sampled 22,398 fish from 310 species. Community composition was influenced more by water type than habitat. Whitewater communities were distinct from those of blackwaters and clearwaters, with community structure correlated strongly to conductivity and turbidity. Mean per-sampling event species richness and biomass were significantly higher in nutrient-rich whitewater floodplain lakes than in oligotrophic blackwater and clearwater river-floodplain systems and light-limited whitewater rivers. Our study provides novel insights into the influences of biogeochemical water type and ecosystem productivity on Earth’s most diverse aquatic vertebrate fauna and highlights the importance of including multiple water types in conservation planning.

亚马逊水域根据溶解的养分含量、沉积物类型、透明度和酸度分为三个生物地球化学类别——所有重要的本地和异地初级生产 (PP) 预测因子：(1) 营养贫乏、低沉积物、高透明度、腐殖质- 染色的酸性黑水；(2) 营养贫乏、低泥沙、高透明度、中性的清水；(3) 营养丰富、透明度低、冲积沉积物、中性白水. 该分类由阿尔弗雷德·拉塞尔·华莱士于 1853 年首次提出，得到了很好的支持，但其对鱼类的影响却知之甚少。为了研究亚马逊鱼类群落组成和物种丰富度如何受到水类型的影响，我们在所有三种水类型共同出现的地方对漫滩湖泊和河边栖息地进行了全年定量采样。我们从 310 个物种中采样了 22,398 条鱼。群落组成受水类型的影响比栖息地的影响更大。白水群落与黑水和清水群落不同，群落结构与电导率和浊度密切相关。营养丰富的白水漫滩湖泊的平均每次采样事件物种丰富度和生物量显着高于贫营养黑水和清水河-漫滩系统以及光照受限的白水河流。我们的研究提供了关于生物地球化学水类型和生态系统生产力对地球上最多样化的水生脊椎动物群的影响的新见解，并强调了在保护规划中包括多种水类型的重要性。