Impacts on surface productivity during sediment dispersal experiment in Central Indian Basin

Abstract

It is anticipated that in the case of mining of marine minerals, sea floor sediments will be brought up along with the mineral ores and discharged on the surface. These nutrient rich sediments would create a set of different physicochemical conditions at the point of discharge thus altering the regimes of productivity in the water column. In order to assess the effects of deep sea sediment discharge on the oceanic surface water-layers (0-50M) after nodule mining, a Sediment Dispersal Experiment (SEDEX) was conducted in Central Indian Basin (CIB). A total of 675 liters of slurry prepared from 225 kg of wet sediment (330 g . l sup(-1)) was discharged on the surface during the experiment. Water samples were collected before and after the discharge to monitor the changes in different environmental parameters. There was a general increase in bacterial abundance and primary producers along with suspended particulate matter. Migration of zooplankton is artificially induced by the stimulatory effect of the sediment and high load of phytoplankton. An increase in diversity, both at the primary and secondary level is noticeable. Within the spatial and temporal frame of observation, waters become net-nitrifying. The influence of the dispersal is apparently more beneficial than harmful on the experimental scale. The results are interesting and warrant more intense effort with long-term observations to evolve predictive models.