ABSTRACT

Surface sediments from three mangrove forests and three adjoining stations of the Cochin estuary were analysed for lipid biomarkers along with bulk parameters to delineate organic matter (OM) sources. Fine-grained sediments dominated in mangrove forests due to low hydrodynamic energy conditions compared to estuaries. The protein/carbohydrate ratio >1 at most of the sites implied that a major fraction of OM was freshly originated. Lipid/carbohydrate ratios >1 indicated the better food quality of OM. Depleted δ¹³C, higher organic carbon-to-nitrogen ratios (>20), tannin and lignin content and lipid biomarkers implied OM inputs from mangrove vegetation. Occurrence of unique mangrove biomarkers like taraxerol in estuarine sediments reflected mangrove input via tidal export of OM. Prominent relative abundance of steroidal ketones, triterpenoid ketones and other degraded triterpenoids pointed towards active diagenetic transformations of sedimentary OM. Significantly higher content of biochemical components and biomarkers in mangrove systems was due to the dominance of fine-grained sediments and better preservation of OM under anoxic conditions. The study could provide baseline information on the significance of OM sequestration and preservation potential of mangrove ecosystems, and hence it is recommended to formulate sustainable management strategies to conserve the existing mangrove forest cover along the Kerala coast.

摘要

分析了来自科钦河口三个红树林和三个相邻站的表层沉积物的脂质生物标志物以及体积参数，以描绘有机物 (OM) 来源。与河口相比，由于水动力条件较低，红树林中的细粒沉积物占主导地位。大多数位点的蛋白质/碳水化合物比率 > 1 表明大部分 OM 是新鲜起源的。脂质/碳水化合物比率 >1 表明 OM 的食品质量更好。耗尽的 δ ¹³C、较高的有机碳氮比（>20）、单宁和木质素含量以及脂质生物标志物暗示来自红树林植被的 OM 输入。在河口沉积物中出现独特的红树林生物标志物如蒲公英醇反映了红树林通过 OM 的潮汐输出输入。甾体酮、三萜酮和其他降解的三萜类化合物的显着相对丰度表明沉积物 OM 的成岩作用活跃。红树林系统中生化成分和生物标志物含量显着增加是由于细粒沉积物占主导地位以及在缺氧条件下对有机质的保存更好。该研究可以提供有关红树林生态系统 OM 封存和保存潜力的重要性的基线信息，