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      https://www.ias.ac.in/article/fulltext/jess/130/0094

    • Keywords

       

      Cold-seep; gas flares; methane hydrate; methane; hydrogen sulfide; chemosymbiont; tubeworm.

    • Abstract

       

      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 $\mu$M) of hydrogen sulfide (H$_{2}$ S) 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 H$_{2}$ S-rich zone. The high concentration of H$_{2}$ S at ${\sim}$ 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 $\delta^{13}$C$_{ CH4}$ values (–28.4 to –79.5per thousand VPDB) suggest a contribution of deep-seated thermogenic methane.

    • Author Affiliations

       

      A MAZUMDAR1 P DEWANGAN1 PEKETI A1 FIROZ BADESAAB1 MOHD SADIQUE1 2 KALYANI SIVAN1 3 JITTU MATHAI1 ANKITA GHOSH1 3 ZATALE A1 3 S P K PILLUTLA1 2 UMA C4 C K MISHRA1 3 WALSH FERNANDES1 ASTHA TYAGI5 TANOJIT PAUL6

      1. Gas Hydrate Research Group, CSIR-National Institute of Oceanography, Dona Paula, Goa 403 004, India.
      2. School of Earth, Ocean, and Atmospheric Sciences, Goa University, Taleigao Plateau, Goa 403 001, India.
      3. Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, Uttar Pradesh 201 002, India.
      4. Kerala University of Fisheries and Ocean Studies, Kochi, Kerala 682 506, India.
      5. K.J. Somaiya College of Science and Commerce, University of Mumbai, Mumbai, Maharashtra 400 077, India.
      6. Manipal Institute of Technology, Manipal, Karnataka 576 104, India.
    • Dates

       
    • Supplementary Material

       
  • Journal of Earth System Science | News

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