Pandey Medhavi, Biswas Haimanti, Schmidt Sabine
CSIR National Institute of Oceanography, Biological Oceanography Division, Dona Paula, Goa, 403004, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India.
CSIR National Institute of Oceanography, Biological Oceanography Division, Dona Paula, Goa, 403004, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India.
Mar Environ Res. 2025 Feb;204:106940. doi: 10.1016/j.marenvres.2024.106940. Epub 2025 Jan 6.
The western Indian continental shelf (eastern Arabian Sea) exhibits contrasting biogeochemical features. This area becomes highly productive due to summer monsoon-driven coastal upwelling in the south and winter monsoon-induced convective mixing in the north. Additionally, in the northern self, the eastern boundary of the Oxygen Minimum Zone (OMZ) persists but is absent in the south. Phytoplankton blooms are dominated by diatoms that contribute to sedimentary phytodetritus flux supplying major elements (C, N, Si) and food for benthic biota and hence important to address. Here we present the data on organic matter content, diatom frustule flux, abundance, and diversity using surface sediments (core tops collected using a multicorer) from 6 locations (11-21° N) along the shelf in a 2° interval at 200 m isobaths. The organic matter retrieved from the core top was relatively fresh (nearly ∼4.5 years old) as evident from Pb profiles. Frustule abundance and diversity (the maximum at 15° N and minimum at 19° N) varied from 0.10-18.46 × 10 valves g and 0.79-2.32, respectively. A total of 36 diatom genera were found with two centric (Thalassiosira and Coscinodiscus), and one pennate (Nitzschia) diatoms as major contributors. The higher contribution of Thalassiosira was observed throughout the shelf dominating the south (11, 13, 15° N), whereas, in the north (17, 19, 21° N) Coscinodiscus was dominant. The highest organic matter content (3.4%) and frustule abundance (18.46 × 10 valves g) were seen at 15° N despite low diatom valve flux (3.3 × 10 valves cm yr) and could be due to the influence of OMZ, where organic matter is well preserved. Contrarily, the upwelling-influenced station in the south (at 11° N) exhibited the highest diatom valve flux (10.14 × 10 valves cm yr), however low organic matter content (1.6 %) and frustule abundance (4.99 × 10 valves g) were attributed to faster mineralization. This study suggested that the preservation potential of organic matter varies across the shelf and is likely to control its recycling, impacting nutrient release and resources for the benthic community.
印度西部大陆架（阿拉伯海东部）呈现出截然不同的生物地球化学特征。由于夏季风驱动的南部沿海上升流和冬季风引发的北部对流混合，该区域生产力极高。此外，在北部陆架，氧含量最小值区（OMZ）的东部边界持续存在，但在南部则不存在。浮游植物大量繁殖以硅藻为主，这些硅藻有助于沉积性浮游植物碎屑通量，为底栖生物群提供主要元素（碳、氮、硅）和食物，因此对该区域的研究很重要。在此，我们展示了沿陆架200米等深线、以2°间隔从6个地点（北纬11° - 21°）采集的表层沉积物（使用多管采样器采集的岩芯顶部样本）的有机质含量、硅藻壳通量、丰度和多样性数据。从岩芯顶部获取的有机质相对新鲜（约4.5年），铅剖面表明了这一点。硅藻壳丰度和多样性（在北纬15°处最高，在北纬19°处最低）分别在0.10 - 18.46×10个壳瓣/克和0.79 - 2.32之间变化。共发现36个硅藻属，其中两个中心硅藻（海链藻属和圆筛藻属）和一个羽纹硅藻（菱形藻属）为主要贡献者。在整个陆架上，海链藻属的贡献较高，在南部（北纬11°、13°、15°）占主导地位，而在北部（北纬17°、19°、21°）圆筛藻属占主导。尽管硅藻壳通量较低（3.3×10个壳瓣/平方厘米·年），但在北纬15°处观察到最高的有机质含量（3.4%）和硅藻壳丰度（18.46×10个壳瓣/克），这可能是由于氧含量最小值区的影响，那里的有机质保存良好。相反，南部受上升流影响的站点（北纬11°）表现出最高的硅藻壳通量（10.14×10个壳瓣/平方厘米·年），然而低有机质含量（1.6%）和硅藻壳丰度（4.99×10个壳瓣/克）归因于更快的矿化作用。这项研究表明，陆架上有机质的保存潜力各不相同，并且可能控制其再循环，影响营养物质释放和底栖生物群落的资源。
