In 1999 an experimental study was initiated in the western Pacific to evaluate the direct impacts of a mining machine on benthic organisms. An artificial disturbance was created, and the abundance and distributions of benthic fauna were compared with a control area. Metazoan meiobenthos were significantly less abundant after the disturbance than at the site prior to disturbance. In addition, following the disturbance, the vertical distribution of metazoan meiobenthos had changed. Given these results, it is inferred that the mining machine adversely affected the benthos, especially the fauna living in surface.


During the 1990s, several countries have conducted experimental studies on the environmental impacts of manganese nodule mining. These studies have focused on the impacts on resulting from rapid deposition of sediment caused by production of a dense suspended sediment plume (Fukushima, 1995, Thiel et al., 1995, Trueblood and Ozturgut, 1997, Kotlinski and Tkatchenko, 1997, Sharma, 1999). However experimental studies focusing on the direct impact of mining machines on benthic organisms, have not been conducted before in tile deep-sea. In addition, (previous experiments were conducted only on the abyssal plains in the central and Southeast Pacific or in the Indian Ocean. Given this background, in 1999, the Metal Mining Agency of Japan (MMAJ) initiated a new benthic-impact experiment to evaluate direct impacts of a mining machine on benthic organisms on the slope of a seamount.

1. Disturbance process

The experiment was carried out from April 24 to 30, 1999, during the cruise of R / V Hakurei-maru NO2. The study site was selected in the western Pacific near Minami-Tori-Shima Island, at a depth of approximately 2,200m (Okubo, 1999). To modify the direct impact of a mining machine on benthos, we made new gear to remove the surface layer of the deep-sea sediment (ie., a scraper).

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