ABSTRACT:

Transition ecosystem area from chemosynthetic community at active hydrothermal venting site to normal seafloor one is the expected place of mining seafloor massive sulfides. No data is available for the distribution characteristics of ecosystems in the transition area. Using visual seafloor observation data obtained by a towed camera system, a preliminary approach to quantify the distribution characteristics of chemosynthetic and transition ecosystems is presented. An example calculation result is introduced.

INTRODUCTION

Kuroko-type seafloor massive sulfides (SMS) in the western Pacific have received much attention as resources for gold, silver, copper, zinc, and lead for the commercial mining by private companies (http://www.nautilusminerals.com; http://www.neptuneminerals.com). Since the first discovery in the Okinawa Trough near Japan (Halbach et al, 1989), SMS have been found in the back-arc basin and on oceanic island-arc areas at 1 to 2 km of water depths. The typical representatives found are on the Izu-Ogasawara Arc near Japan (Iizasa et al. 1999), in the Lau Basin and the North Fiji Basin near Fiji (Fouquet et al., 1991; Bendel et al, 1993), and in the East Manus Basin near Papua New Guinea (Kia and Lasark, 1999). The high gold, silver, and copper contents in the East Manus Basin have increased the likelihood that mining would be profitable, and a pioneer commercial mining operation with 6,000 t/d in production scale was scheduled to start in a few years (http://www.nautilusminerals.com). However, the baseline data provided in the environmental impact statement (EIS) presented to Papua New Guinea Government (http://www.nautilusminerals.com) was insufficient for quantifying the distribution characteristics of chemosynthetic and transition ecosystems. The approaches they took for the EIS were conventional style scientific observations conducted by ROVs, and many biological samplings for megabenthos such as shrimps, crabs, shellfishes, and tubeworms. The analyses were also scientific style classification, distribution mapping, genome analysis, etc.

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