Here, we report for the first time, the genus Lamellibrachia tubeworm and associated chemosynthetic ecosystem from a cold-seep site in the Indian Ocean. The discovery of cold-seep was made off the Cauvery–Mannar Basin onboard ORV Sindhu Sadhana (SSD-070; 13th to 22nd February 2020). The chemosymbiont bearing polychaete worm is also associated with squat lobsters (Munidposis sp.) and Gastropoda belonging to the family Buccinidae. Relict shells of chemosynthetic Calyptogena clams are ubiquitous at the seep sites. The Lamellibrachia tubes were found to be firmly anchored into the authigenic carbonate crusts. The authigenic carbonate crusts (chemoherm) are packed with large Calyptogena shells (whole shell and fragments). Very high concentrations (3800–12900 µM) of hydrogen sulfide (H₂S) in the interstitial waters (40 cmbsf) is responsible for the sustenance of chemosymbiont bearing tubeworms. The posterior end of the tube penetrates downwards into the H₂S-rich zone. The high concentration of H₂S at ~40 cmbsf is attributed to sulfate reduction via anaerobic oxidation of methane (AOM) pathway. Methane hydrate was observed within the faults/fractures in the sediments. The presence of ethane and propane along with methane in the headspace gases and δ¹³C_CH4 values (–28.4 to –79.5‰ VPDB) suggest a contribution of deep-seated thermogenic methane.

在这里，我们首次报告了印度洋冷寒地区的Lamellibrachia夜蛾属和相关的化学合成生态系统。冷深的发现是在ORV Sindhu Sadhana号（SSD-070； 2020年2月13日至22日）上的Cauvery-Mannar盆地附近发现的。带有化学共生蛋白的多毛et蠕虫还与属于龙虾科的蹲龙虾（Munidposis sp。）和腹足纲动物有关。化学合成Calyptogena蛤的遗壳在渗水部位无处不在。所述Lamellibrachia发现管被牢固地锚定到自生碳酸盐结壳。自生碳酸盐结壳（chemoherm）被填充有大Calyptogena贝壳（整个贝壳和碎片）。间隙水（40 cmbsf）中硫化氢（H ₂ S）的浓度很高（3800–12900 µM），这是导致携带化学型共生结节虫的原因。管的后端向下渗透到富H ₂ S区域。约40 cmbsf的H ₂ S高浓度归因于甲烷的厌氧氧化（AOM）途径使硫酸盐还原。在沉积物的断层/断裂中观察到甲烷水合物。乙烷和丙烷的连同在顶部空间气体甲烷和存在δ ^13倍Ç _CH4的值（-28.4至-79.5‰VPDB）建议根深蒂固产热甲烷的贡献。