Evaluation of re-suspended sediments to sinking particles by benthic disturbance in manganese nodule fields of the Northeastern Pacific

Abstract

The abyssal sediments of the Pacific contain mineral resources of potential commercial and strategic interest: of particular interest are the polymetallic nodules commonly known as manganese nodules. Mining operations discharge resuspended sediment into the water column that inevitably disturbs the marine environments. The impact on the marine ecosystem is thought to depend mainly on the scale of disturbance and the amount of resuspended sediment. However, mining-induced particle resuspension processes in the manganese nodule fields are poorly understood. The geochemical properties of sinking particles and sediments in the Clarion-Clipperton Zone were examined to develop a quantitative indicator with which to evaluate the contribution of sediment resuspended by nodule mining activity to sinking particles. The ratio of lithogenic material to organic carbon varies from ~3 in sinking particles to ~211 in sediments. This ratio is easily measured and is not easily affected by degradation and/or dissolution in the water column. A mixing model indicates that the ratio may be used as a potential proxy for estimating the contribution of resuspended sediment derived from mining operations to sinking particles. However, this indicator will need to be examined further, and should be validated against real data from perturbation experiments in the future. sediment into the water column that inevitably disturbs the marine environments. The impact on the marine ecosystem is thought to depend mainly on the scale of disturbance and the amount of resuspended sediment. However, mining-induced particle resuspension processes in the manganese nodule fields are poorly understood. The geochemical properties of sinking particles and sediments in the Clarion-Clipperton Zone were examined to develop a quantitative indicator with which to evaluate the contribution of sediment resuspended by nodule mining activity to sinking particles. The ratio of lithogenic material to organic carbon varies from ~3 in sinking particles to ~211 in sediments. This ratio is easily measured and is not easily affected by degradation and/or dissolution in the water column. A mixing model indicates that the ratio may be used as a potential proxy for estimating the contribution of resuspended sediment derived from mining operations to sinking particles. However, this indicator will need to be examined further, and should be validated against real data from perturbation experiments in the future.1