title: Monitoring the sedimentary carbon in an artificially disturbed deep-sea sedimentary environment.
abstract: An area of 0.6 km(2) in the manganese nodule field of the Central Indian Basin was physically disturbed and sediments discharged in the near bottom waters to simulate seabed mining and study its impact on benthic ecosystem. An estimated 2 to 3 tonnes of sedimentary organic carbon (C(org)) was resuspended into the water column during a 9-day experiment. The majority of the sediment cores from within the disturbed area and areas towards the south showed a ~30% increase in C(org) content as well as an increase in carbon burial rates after disturbance, though with a reduction in carbon/phosphorus ratios. High specific surface area (SSA~25 m(2) g(-1)) and low C(org)/SSA ratios (mostly <0.5) are typical of deep-sea sediments. The increased C(org) values were probably due to the organic matter from dead biota and the migration and redeposition of fine-grained, organic-rich particles. Spatial distribution patterns of C(org) contents of cores taken before and after disturbance were used to infer the direction of plume migration and re-sedimentation. A positive relationship was observed between total and labile C(org) and macrobenthos density and total bacterial numbers prior to disturbance, whereas a negative relationship was seen after disturbance owing to drastic reduction in the density of macrofauna and bacteria. Overall decrease in labile organic matter, benthic biota and redistribution of organic matter suggest that the commercial mining of manganese nodules may have a significant immediate negative effect on the benthic ecosystem inducing changes in benthic community structure.
authors.affiliation: National Institute of Oceanography, Council of Scientific & Industrial Research, Dona Paula, Goa, 403 004, India. nagender@nio.org
authors.forename: B Nagender
authors.initials: BN
authors.lastname: Nath
authors.forename: N H
authors.initials: NH
authors.lastname: Khadge
authors.forename: Sapana
authors.initials: S
authors.lastname: Nabar
authors.forename: Chandralata
authors.initials: C
authors.lastname: Raghukumar
authors.forename: B S
authors.initials: BS
authors.lastname: Ingole
authors.forename: A B
authors.initials: AB
authors.lastname: Valsangkar
authors.forename: Rahul
authors.initials: R
authors.lastname: Sharma
authors.forename: K
authors.initials: K
authors.lastname: Srinivas
mesh_terms: D002244:Carbon / Q000032:analysis*; D017753:Ecosystem; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000737:chemistry*; D019156:Indian Ocean; D008956:Models, Chemical; D010758:Phosphorus / Q000032:analysis; D012623:Seawater / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000706:statistics & numerical data
chemical_list: D014874:Water Pollutants, Chemical; D010758:Phosphorus; D002244:Carbon