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mining system would remain suspended for months or years,
measurements showed that that was not so. Further, the top 20 cm of the
benthos in the track had been disturbed, but it remained to be seen when
conditions would return to their original level. The first set of information
after the immediate post-disturbance scenario showed that the effects were
restricted to 100 m from the track and about 5 m above the seabed. His
conclusion was that the situation was not very alarming. India would take
its decision when all the data were together and it could discuss with other
people about their experiences and consult with the Authority as well.
Biological impact
Asked whether there were plans to look at the species density of
macrobenthos samples, Ravindran replied that a specialist on microbiology
and marine biology would conduct taxonomic research as part of the study.
Ten papers had already been published and more were in the pipeline.
Asked about sediment profiles before and after the disturbance,
and particularly whether the indirect impact from resedimentation had been
taken into account, Ravindran said that some of the initial results were
contradictory. For example, in some areas the benthic density had
increased, though on average there had been a reduction within the track
area. Some variability was inevitable, given the fact that the positioning
system had an accuracy of ±30-40 m and the observations were at a depth
of 6000 m.
The limited measurements and analysis done so far concerned the
situation immediately after the disturbance, not one or two years later.
Measurements of data from the reference site would come subsequently
and should throw more light on the indirect impact in the long term. The
immediate impact concerned such matters as when the sediment settled,
how much benthic mass in the track had been lost and how much
transmissivity had declined. Other aspects, such as soil strength, were not
much affected. With the use of an environmentally friendly collector and
crawler, the impact would be less.
The moderator, Professor Craig Smith, said it was important to
understand the cause of the significant change reported in the benthic
fauna. The track area was a 200-m wide swath over which the 2-m wide
disturber had been dragged for 26 tows. There had been some
combination of direct removal of sediment and resedimentation within the
track area. The impact within the track was probably less than would occur
184 INTERNATIONAL SEABED AUTHORITY