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second part of BIE, beginning in 2001, Yuzhmorgeologia had started its own
ecological investigation in the Russian Experimental Polygon (REP). In
selecting the site for the BIE experiment, the researchers had looked for an
area of clear sediment without manganese nodules or with low nodule
density.
Sediment disturbance associated with nodule mining would create
in the first place an impact on the benthic community. It was presumed
that benthic organisms would be influenced by direct physical contact with
the mining device, burial under a layer of resuspended sediment and a
decrease in available food. The need to study this problem before
commercial mining took place in the Clarion-Clipperton Fracture Zone
(CCFZ) had been the main motivation for several international model
experiments impacting the deep-sea benthos, including BIE, the Japan
Deep-Sea Impact Experiment (JET), the Indian Deep-sea Environment
Experiment (INDEX) and work done by IOM.
The main design of the Russian experiment had been to create a
relatively large disturbance of the upper sediment layer, using a miningsimulation
device, in order to investigate the ecosystem’s response to the
disturbance immediately and some years afterward. The project had
included baseline investigation within the selected polygons, the benthic
ecosystem disturbance itself, and monitoring of the disturbed site and a
reference site. The studies had been carried out immediately after the
disturbance, one year later and seven years later – close to the timetable of
the DISCOL experiment. The resuspended sediment plume had been
tracked using near-bottom CTD (conductivity-temperature-depth) profiles.
The thickness of the resuspended sediment had been measured with
sediment traps, current-meter stations, transmissometers and X-ray photos
of sediment cores. Locations of all underwater devices had been fixed with
a global positioning system (GPS) using navigation satellites and an
acoustic underwater navigation system, ASMOD, created within
Yuzhmorgeologia. At the centre of the experiment was the disturber,
designed by the United States firm Sound Ocean Systems, Inc. That
company had created a first generation disturber, and for the BIE-II
experiment it had built a more powerful second generation device. A similar
device had been lost during the Japanese experiment. All BIE cruises had
been carried out on the Russian vessel Yuzhmorgeologia, a large capacity
ship of 5600 tons with a big bottom tank and an excellent wire-cable winch.
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