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<p>Active cold seep sites associated with shallow methane hydrates, methane gas flares in the water column, and cold seep ecosystems have been reported from the Krishna-Godavari (K-G) basin along the eastern continental margin of India, and the present study represents the first attempt to map and demarcate these cold seep ecosystems in the region. An autonomous underwater vehicle survey was conducted at two cold seep locations (SN184/KG-1, water depth: ~ 1750 and SN184/KG-2, water depth: ~ 950&#xa0;m) in the Krishna-Godavari basin, to understand the water column methane concentrations along with seabed survey using underwater photographic studies. A cold seep ecosystem is found only at SN184/KG-1. The dissolved methane concentrations at SN184/KG-1 vary from 0.18–1.48 µmol/L, while at SN184/KG-2 it varies from 0.14–0.5 µmol/L. The underwater photographs from the AUV show the presence of methane hydrates on the seabed, bubbling of methane gas, and a large cold seep ecosystem extending to several square meters. Very high dissolved methane concentrations in the water column may be attributed to gas bubbling from the cold seeps. The cold seep ecosystem is predominantly populated with <i>Bathymodiolus</i> species along with the presence of tube worms (Siboglinidae), goose barnacles, etc. At SN184/KG-1 there are fluctuations in the water column pH possibly induced by methane oxidation. Although enhanced water column methane concentrations, and surface hydrates coupled with carbonate crusts are observed at SN184/KG-2, the lack of benthic community at SN184/KG-2 may be attributed to the occurrence of very high sedimentation at this site because of mass transport deposits in recent times. The present study adds up a new methane seepage site and provides baseline database to quantify methane addition to global ocean.</p>

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Cold seep induced elevated water column methane concentrations in Krishna-Godavari basin, Bay of Bengal

  • 期刊论文

  • 发表日期：

    2026年1月3日

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  • A. Peketi,
  • G. Sriram,
  • S. Ramesh,
  • N. R. Ramesh,
  • S. Mishra,
  • P. Dewangan,
  • V. B. Subin Raj,
  • M. A. Sarun Lal,
  • A. Zatale,
  • A. Mazumdar

摘要

Active cold seep sites associated with shallow methane hydrates, methane gas flares in the water column, and cold seep ecosystems have been reported from the Krishna-Godavari (K-G) basin along the eastern continental margin of India, and the present study represents the first attempt to map and demarcate these cold seep ecosystems in the region. An autonomous underwater vehicle survey was conducted at two cold seep locations (SN184/KG-1, water depth: ~ 1750 and SN184/KG-2, water depth: ~ 950 m) in the Krishna-Godavari basin, to understand the water column methane concentrations along with seabed survey using underwater photographic studies. A cold seep ecosystem is found only at SN184/KG-1. The dissolved methane concentrations at SN184/KG-1 vary from 0.18–1.48 µmol/L, while at SN184/KG-2 it varies from 0.14–0.5 µmol/L. The underwater photographs from the AUV show the presence of methane hydrates on the seabed, bubbling of methane gas, and a large cold seep ecosystem extending to several square meters. Very high dissolved methane concentrations in the water column may be attributed to gas bubbling from the cold seeps. The cold seep ecosystem is predominantly populated with Bathymodiolus species along with the presence of tube worms (Siboglinidae), goose barnacles, etc. At SN184/KG-1 there are fluctuations in the water column pH possibly induced by methane oxidation. Although enhanced water column methane concentrations, and surface hydrates coupled with carbonate crusts are observed at SN184/KG-2, the lack of benthic community at SN184/KG-2 may be attributed to the occurrence of very high sedimentation at this site because of mass transport deposits in recent times. The present study adds up a new methane seepage site and provides baseline database to quantify methane addition to global ocean.