Extensive floodplains and numerous lakes in the Amazon basin are well suited to examine the role of floodable lands within the context of the sources and processing of carbon within inland waters. We measured diel, seasonal and inter-annual variations of CO₂ concentrations and related environmental variables in open water and flooded vegetation and estimated their habitat area using remote sensing in a representative Amazon floodplain lake, Lake Janauacá. Variability in CO₂ concentrations in open water resulted from changes in the extent of inundation and exchange with vegetated habitats. Depth-averaged values of CO₂ in the open water of the lake, 157 ± 91 µM (mean ± SD), were less than those in an embayment near aquatic vegetation, 285 ± 116 µM, and were variable over 24-h periods at both sites. Within floating herbaceous plant mats, the mean concentration was 275 ± 77 µM, while in flooded forests it was 217 ± 78 µM. The best statistical model that included CO₂ in aquatic plant mats, water clarity, rate of change in water level and chlorophyll-a concentrations explained around 90% of the variability in CO₂ concentration. Three-dimensional hydrodynamic modeling demonstrated that diel differences in water temperature between plant mats and open water as well as basin-scale motions caused lateral exchanges of CO₂ between vegetated habitats and open water. Our findings extend understanding of CO₂ in tropical lakes and floodplains with measurements and models that emphasize the importance of flooded forests and aquatic herbaceous plants fringing floodplain lakes as sources of CO₂ to open waters.

亚马逊流域广阔的洪泛区和众多湖泊非常适合在内陆水域内碳的来源和加工的背景下检查可泛滥土地的作用。我们测量了开阔水域和淹没植被中 CO ₂浓度和相关环境变量的_日变化、季节性和年际变化，并在具有代表性的亚马逊洪泛区湖泊 Janauacá 中使用遥感估算了它们的栖息地面积。开放水域中 CO ₂浓度的变化是由于淹没程度的变化以及与植被栖息地的交换造成的。CO _{2 的}深度平均值在湖泊的开阔水域中，157 ± 91 µM（平均值 ± SD），小于水生植被附近的海湾中的 285 ± 116 µM，并且在两个地点的 24 小时内都发生了变化。在漂浮的草本植物垫中，平均浓度为 275 ± 77 µM，而在水淹森林中为 217 ± 78 µM。该包括CO的最佳统计模型₂在水生植物垫，水清楚起见，在水位变化率和受叶绿素一个浓度CO解释的变异的90％左右₂浓度。三维流体动力学模型表明，植物垫和开阔水域之间的水温差异以及盆地尺度运动导致了 CO _{2 的}横向交换在植被栖息地和开阔水域之间。我们的研究结果通过测量和模型扩展了对热带湖泊和漫滩中 CO _{2 的}理解，这些测量和模型强调了泛滥平原湖泊边缘的淹没森林和水生草本植物作为开放水域CO ₂来源的重要性。