ABSTRACT:

In 1994, the Metal Mining Agency of Japan began the Japan Deep-Sea Impact Experiment (JET) in Japan" s western mining claim area in the Central Pacific, to assess the impact of mining deposition on the benthic ecosystem. The abundance of meiofauna was monitored before, just after, and one and two years after the JET experiment in areas without deposits, and in those with light, moderate, and heavy deposits. In the post-disturbance survey two years after the experiment, the macro- and megabenthos were also studied. Immediately after the experiment, the abundance of meiofauna decreased drastically where deposition had occurred, but by two years later numbers had returned to original levels and differences were not found between the affected and control areas. All sizes of deposit-feeding benthos were more susceptible to the artificial deposition of sediments than filter feeders.

INTRODUCTION

The Metal Mining Agency of Japan conducted the Japan Deep-Sea Impact Experiment (JET) in Japan" s western mining claim area in the Central Pacific Ocean for three years, from 1994–1996. The objective of the research was to evaluate the impact that rapid deposition caused by a deep-sea mining operation would have on abyssal benthic organisms and their environment (Kajitani, 1997). The study was undertaken in four phases: one pre-disturbance survey (JET 1, July 1995) and three post-disturbance surveys. A benthic disturber was used from August to September 1995 to artificially create rapid deposition, simulating the effect of the plume that is created during manganese nodule mining. This disturber has also been used in other projects, such as BIE (Trueblood and Ozturgut, 1997). The first post-disturbance survey was carried out immediately afterwards (JET 2, September 1995); the second one year later (JET 3, September 1996); and the last two years after the disturbance (JET 4, September 1997).

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