Seasonal anoxia over the western Indian continental shelf

Show simple item record Naqvi, S.W.A. Naik, H. Jayakumar, A. Pratihary, A.K. Narvenkar, G. Kurian, S. Agnihotri, R. Shailaja, M.S. Narvekar, P.V. 2009-12-22T10:00:19Z 2009-12-22T10:00:19Z 2009
dc.identifier.citation In "Indian Ocean biogeochemical processes and ecological variability. eds. by: Wiggert, J.D.; Hood, R.R.; Naqvi, S.W.A.; Brink, K.H.; Smith, S.L.", 333-345p.
dc.identifier.other no
dc.description.abstract The eastern Arabian Sea contains the only eastern-boundary-type upwelling environment in the entire Indian Ocean, albeit on a seasonal basis. During the southwest monsoon, when the surface current flows equatorward, upwelling brings oxygen-poor, nutrient-rich subsurface waters to the Indian continental shelf that turn anoxic (sulfate-reducing) by late summer due to exhaustion of oxygen and nitrate by heterotrophic microorganisms. This natural oxygen-deficient system, by far the world’s largest in the coastal ocean, is apparently more intense now than it was three decades ago. This is consistent with the sedimentary record, which indicates that productivity over the past few decades has been the highest ever in the last seven centuries. However, a trend of ongoing intensification is not seen in the data collected during the last 10 years at a coastal time series station off Goa. These data, nevertheless, show considerable interannual variability with the most severe anoxia having occurred in 2001, adversely impacting local fisheries (especially demersal fish catch). While increased nutrient loading to the coastal zone largely through atmospheric deposition of nitrogen most likely occurred in the last few decades, contributing to a shift to fully anoxic conditions, the observed interannual variability suggests that subtle changes in local hydrography/circulation could also modulate coastal anoxia in the region
dc.language.iso en
dc.publisher American Geophysical Union
dc.rights Copyright [2009] AGU. All efforts have been made to respect the copyright to the best of our knowledge. Inadvertent omissions, if brought to our notice, stand for correction and withdrawal of document from this repository.
dc.subject Seasonal anoxia
dc.subject Indian Ocean
dc.subject heterotrophic microorganisms
dc.subject nutrient loading
dc.title Seasonal anoxia over the western Indian continental shelf
dc.type Book Chapter

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