4.2 Environmental studies for deep-sea polymetallic nodule deposits
As a result of the exploration for polymetallic nodules, an area of 150,000 sq.km with promising deposits was identified in the Central Indian Basin (CIB). Arising from the need for evaluation of environmental data for designing a mining system as well as for prediction of potential impact of mining on marine ecosystem, the project on ‘EIA studies for nodule mining in CIB’ was initiated in 1996.
Mining of the deep-sea minerals is expected to alter the environmental conditions in the marine ecosystem. The impact of offshore mining would be due to the sediment plume at the seafloor, turbidity in the water column and addition of bottom sediments to the surface resulting in change in the marine ecosystem. The adjacent areas will not only have higher sedimentation rates, but the suspended loads may remain for over long periods but also travel laterally, causing clogging of filter feeding apparatus of benthic organisms in the area. Sudden increase in the amount of suspended matter due to sediment plume and mining discharge, will increase the turbidity of these waters, and may also affect pelagic organisms.
The debris and sediments mixed with water, which are lifted and transported with the minerals, will be discharged at the surface, and create turbidity. Their dispersion by currents will decrease the available sunlight for photosynthesis causing long term effects on biological productivity. At the same time introduction of bottom water, with its higher nutrient values, could result in artificial upwelling, increasing the surface productivity. Discharge of tailings and effluent below the oxygen-minimum zone may cause some environmental harm to the pelagic fauna. If tailings consisting of sediments (including clay) and effluent are discharged in near-surface waters then there are additional impacts, such as reduction in primary productivity due to shading of phytoplankton and effects on phytoplankton from trace metals and on behaviour of marine mammals and especially the duration of tailing suspension, especially with at-sea processing.
Phases of the program
Phase I : Baseline data collection in test and reference areas (1995-1997)
Phase II : Benthic disturbance & impact assessment (1997-2001)
- Phase III : Monitoring of restoration of benthic environment, modeling of sediment plume dispersal and creation of environmental database (2001-2007)
-
- Phase IV : Characterisation of environmental conditions associated with deep-sea nodule deposits and preparation of environment management plan (2007-2012).
4.2 Environmental studies for deep-sea polymetallic nodule deposits
As a result of the exploration for polymetallic nodules, an area of 150,000 sq.km with promising deposits was identified in the Central Indian Basin (CIB). Arising from the need for evaluation of environmental data for designing a mining system as well as for prediction of potential impact of mining on marine ecosystem, the project on ‘EIA studies for nodule mining in CIB’ was initiated in 1996.
Mining of the deep-sea minerals is expected to alter the environmental conditions in the marine ecosystem. The impact of offshore mining would be due to the sediment plume at the seafloor, turbidity in the water column and addition of bottom sediments to the surface resulting in change in the marine ecosystem. The adjacent areas will not only have higher sedimentation rates, but the suspended loads may remain for over long periods but also travel laterally, causing clogging of filter feeding apparatus of benthic organisms in the area. Sudden increase in the amount of suspended matter due to sediment plume and mining discharge, will increase the turbidity of these waters, and may also affect pelagic organisms.
The debris and sediments mixed with water, which are lifted and transported with the minerals, will be discharged at the surface, and create turbidity. Their dispersion by currents will decrease the available sunlight for photosynthesis causing long term effects on biological productivity. At the same time introduction of bottom water, with its higher nutrient values, could result in artificial upwelling, increasing the surface productivity. Discharge of tailings and effluent below the oxygen-minimum zone may cause some environmental harm to the pelagic fauna. If tailings consisting of sediments (including clay) and effluent are discharged in near-surface waters then there are additional impacts, such as reduction in primary productivity due to shading of phytoplankton and effects on phytoplankton from trace metals and on behaviour of marine mammals and especially the duration of tailing suspension, especially with at-sea processing.
Phases of the program
Phase I : Baseline data collection in test and reference areas (1995-1997)
Phase II : Benthic disturbance & impact assessment (1997-2001)
- Phase III : Monitoring of restoration of benthic environment, modeling of sediment plume dispersal and creation of environmental database (2001-2007)
-
- Phase IV : Characterisation of environmental conditions associated with deep-sea nodule deposits and preparation of environment management plan (2007-2012).
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