Anaerobic Carbon Mineralisation Through Sulphate Reduction in the Inner Shelf Sediments of Eastern Arabian Sea
Anaerobic Carbon Mineralisation Through Sulphate Reduction in the Inner Shelf Sediments of Eastern Arabian Sea
复制标题
东阿拉伯海内陆架沉积物中硫酸盐还原的厌氧碳矿化
DOI：
10.1007/s12237-016-0130-0
复制
发表时间：
2016
影响因子：
2.7
通讯作者：
J. Araujo
中科院分区：
文献类型：
--
作者：
R. Naik;S. Naqvi;J. Araujo
季风引起的沿海涌升、陆地径流、海底和大气输入使西印度大陆架沃茨具有生物生产力，预计将导致沉积物中有机物（OM）矿化率高。异化硫酸盐还原（SR）是近岸海洋沉积物中有机质矿化的主要途径，这是由于沉积物-水界面几毫米内其他能量更有利的电子受体（O2，NO3−，Mn和Fe氧化物）的耗尽。我们进行了有史以来第一次研究，以量化SR率在内陆架沉积物关闭果阿（印度中西部海岸）使用35 S放射性示踪技术。最高比率记录在沉积物芯的上部10厘米处，此后逐渐下降，低于检测值。尽管大多数地点的上部12至21厘米处存在显着的SR活动，但孔隙水硫酸盐浓度通常并未随深度显示出太大变化。深度综合SR率（0.066-0.46 mol m−2年−1）随水深增加而降低。在浅水站（深度<30米）的孔隙沃茨中，游离硫化物浓度较低（0-3微米）。然而，在沉积物-水界面以下7-11厘米的两个较深的站点（39米和48米深），观察到孔隙沃茨中硫化物（100-600微米）的高度积聚。沉积物中的总铁含量从最浅的站到最深的站从0.7%降低到5%。高黄铁矿含量表明，陆架沉积物作为硫化物的汇占孔隙水中游离硫化物水平低。在果阿外海中等有机质含量（2- 3.5%）的沉积物中，测得的SR速率远低于其他涌升区，特别是纳米比亚和秘鲁外海。通过硫酸盐还原反应生成的有机碳量为1.052 mol m−2 year−1。据估计，有机碳的平均积累速率为2.56（±0.5）mol m−2年−1，这表明研究区域的大部分有机质都保存在沉积物中。
Monsoon-induced coastal upwelling, land run-off, benthic and atmospheric inputs make the western Indian shelf waters biologically productive that is expected to lead to high rates of mineralisation of organic matter (OM) in the sediments. Dissimilatory sulphate reduction (SR) is a major pathway of OM mineralisation in near-shore marine sediments owing to depletion of other energetically more profitable electron acceptors (O2, NO3−, Mn and Fe oxides) within few millimetres of the sediment-water interface. We carried out first ever study to quantify SR rates in the inner shelf sediments off Goa (central west coast of India) using the 35S radiotracer technique. The highest rates were recorded in the upper 10 cm of the sediment cores and decreased gradually thereafter below detection. Despite significant SR activity in the upper ∼12 to 21 cm at most of the sites, pore water sulphate concentrations generally did not show much variation with depth. The depth integrated SR rate (0.066–0.46 mol m−2 year−1) decreased with increasing water depth. Free sulphide was present in low concentrations (0–3 μM) in pore waters at shallow stations (depth <30 m). However, high build-up of sulphide (100–600 μM) in pore waters was observed at two deeper stations (depths 39 and 48 m), 7–11 cm below the sediment-water interface. The total iron content of the sediment decreased from ∼7 to 5 % from the shallowest to the deepest station. The high pyrite content indicates that the shelf sediments act as a sink for sulphide accounting for the low free sulphide levels in pore water. In the moderately organic rich (2–3.5 %) sediments off Goa, the measured SR rates are much lower than those reported from other upwelling areas, especially off Namibia and Peru. The amount of organic carbon remineralised via sulphate reduction was ∼0.52 mol m−2 year−1. With an estimated average organic carbon accumulation rate of ∼5.6 (±0.5) mol m−2 year−1, it appears that the bulk of organic matter gets preserved in sediments in the study region.