ABSTRACT Carbon and nitrogen stable isotope compositions (δ13C and δ15N) of organic matter (OM) and total organic carbon to total nitrogen ratio (Corg/TN) in a sediment core collected in Sagua estuary (Cuba), were investigated to elucidate the origin of the Sedimentary OM (SOM) and changes in its main sources, over the last 100 years. Results showed almost constant values in the elemental and isotope composition of SOM from 1908 to 1970 with an abrupt change after 1970. From 1970 to 2005, δ13C increased from -21.2 up to -19.3 ‰, while δ15N declined from 1.5 to values close to 0 ‰. The output of the mass-balance model for the identification of OM sources indicated that δ13C and Corg/TN values are generally influenced by marine Particulate OM (POM) sources. Between 1900 and 1970, the main OM source in sediments was marine POM (>85 %), with freshwater POM contributing ca. 15%. Since 1970, the establishment of the Alacranes Dam determined drastic environmental changes influencing the OM sources in the area. Mixing models pointed to seagrasses (79 %) as the main contributors to SOM in the first period, while since 1973 onward, the contribution of human-derived sources such as fertilizers and urban discharges became greater. This information can provide baseline data for the environmental management of the Sagua watershed.

中文翻译：

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碳和氮同位素用于区分加勒比河口沉积有机质的来源

摘要 研究了收集在 Sagua 河口（古巴）的沉积岩芯中有机质 (OM) 的碳和氮稳定同位素组成 (δ13C 和 δ15N) 和总有机碳与总氮的比率 (Corg/TN)，以阐明其起源。沉积 OM (SOM) 及其主要来源的变化，在过去 100 年中。结果表明，SOM 的元素和同位素组成在 1908 年至 1970 年期间几乎保持不变，而在 1970 年之后发生了突变。从 1970 年到 2005 年，δ13C 从 -21.2 增加到 -19.3 ‰，而 δ15N 从 1.5 下降到接近 0 的值‰。用于识别 OM 源的质量平衡模型的输出表明 δ13C 和 Corg/TN 值通常受海洋微粒 OM (POM) 源的影响。1900 年至 1970 年间，沉积物中的主要 OM 来源是海洋 POM（>85%），淡水POM贡献约。15%。自 1970 年以来，阿拉克拉内斯大坝的建立决定了影响该地区 OM 源的剧烈环境变化。混合模型指出，海草 (79%) 是第一阶段 SOM 的主要贡献者，而自 1973 年以来，化肥和城市排放等人为来源的贡献变得更大。这些信息可以为 Sagua 流域的环境管理提供基线数据。化肥和城市排放等人为来源的贡献变得更大。这些信息可以为 Sagua 流域的环境管理提供基线数据。化肥和城市排放等人为来源的贡献变得更大。这些信息可以为 Sagua 流域的环境管理提供基线数据。