Long-Term Monitoring of Environmental Conditions of Benthic Impact Experiment

The Japan Deep-Sea Impact Experiment (JET) is an in situ experiment aimed at evaluating the environmental impacts and recovery process arising from associated manganese nodule mining. The experiment was initiated in 1994 and ended in 1996. However, owing to the short monitoring period, it was not possible to gain adequate understanding of the recovery process. Subsequently, the Deep Ocean Resources Development Co., Ltd., revisited the site 17–18 years later and surveyed the environmental conditions (long-term monitoring survey). This survey found that the environmental impacts that were recognizable immediately after and 1 year after benthic disturbance were not visible after 17–18 years. This chapter presents the results of the long-term monitoring survey and discusses future plans of environmental impact evaluations.