Given the importance of dissolved organic matter (DOM) in the carbon cycling of aquatic ecosystems, information on its seasonal variability is crucial. In this study we assess the use of optical absorption indices available in the literature based on in situ data to both characterize the seasonal variability of DOM in a highly complex environment and for application in large-scale studies using remote sensing data. The study area comprises four lakes located in the Mamirauá Sustainable Development Reserve (MSDR). Samples for the determination of colored dissolved organic matter (CDOM) and measurements of remote sensing reflectance (R_rs) were acquired in situ. The R_rs was used to simulate the response of the visible bands of the Sentinel-2 MultiSpectral Instrument (MSI), which was used in the proposed models. Differences between lakes were tested using the CDOM indices. The results highlight the role of the flood pulse in the DOM dynamics at the floodplain lakes. The validation results show that the use of the absorption coefficient of CDOM (a_CDOM) as a proxy of the spectral slope between 275 and 295 nm (S_275–295) during rising water is worthwhile, demonstrating its potential application to Sentinel-2 MSI imagery data for studying DOM dynamics on the large scale.

中文翻译：

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利用光吸收指数评估亚马逊洪泛区湖泊中溶解有机物的季节性变化

鉴于溶解性有机物（DOM）在水生生态系统的碳循环中的重要性，有关其季节性变化的信息至关重要。在这项研究中，我们评估了基于原位数据的文献中可用的光吸收指数的使用，以表征高度复杂环境中DOM的季节性变化，并用于使用遥感数据的大规模研究中。研究区域包括位于Mamirauá可持续发展保护区（MSDR）中的四个湖泊。原位获取用于测定有色溶解有机物（CDOM）和测量遥感反射率（R _rs）的样品。在[R _RS用于模拟Sentinel-2多光谱仪（MSI）可见波段的响应，该波段用于所提出的模型。使用CDOM指数测试了湖泊之间的差异。结果突出了洪水脉冲在洪泛区湖泊DOM动力学中的作用。验证结果表明，使用CDOM（的吸收系数的一个_CDOM为275和295纳米（之间的光谱的斜率的代理）š _275-295水上升期间）是值得的，展示了其潜在的应用哨兵-2 MSI用于大规模研究DOM动态的图像数据。