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speculate on the rates of recolonisation following a large-scale disturbance
in the deep sea. This phenomenon might be studied by placing trays of
azoic sediment (sediment without animals) on the seafloor, thereby
mimicking the effect of a large-scale disturbance, and then examining the
recolonisation rate over time. Data from such an experiment, using a tray
0.5 cm on a side, showed a slow recovery to background community
conditions (abundance of animals in the surrounding sediment). The data,
applying to macrofauna, were from all around the deep sea, including
depths of 1000-2000 m, in areas that had higher energy flux and
presumably a higher recolonisation rate than the CCFZ. Even in such
productive environments, it took about eight years for the macrofauna to
recolonise. The point was not that such a rate should be applicable to a
mining disturbance but rather that recolonisation rates in the deep sea
were slow following an intense disturbance. The same trays in shallow
water might show a recovery to background conditions in a matter of weeks
to a few months. Whether or not meiofauna showed the same response as
macrofauna, the fact remained that if a deep-sea community were severely
disturbed by removing a high percentage of the fauna over a large area,
recovery times would be lengthy.
It would be important to factor that conclusion into any design of
impact experiments. Even though the DISCOL (Disturbance Recolonization)
and JET (Japan Deep-Sea Impact Experiment) projects and others showed
that the intensity of disturbance in terms of generated plume was moderate
compared to what could be expected from mining, recovery times were long.
Differences in communities could be expected eight years after even the
moderate level of disturbance produced by DISCOL.
Turning next to the high species diversity in the CCFZ, Smith cited
data on polychaete worms – a major component of macrofauna – showing
that a collection of 163 individuals had yielded anywhere from about 47 to
about 82 different species. Thus, on a local scale, diversity was high
compared to many other ecosystems. Implied in that species diversity was
a lot of genetic diversity. Another aspect of diversity that was much more
controversial and difficult to estimate was how many species inhabited a
given region, at each of the collection sites. A post-doctorate scholar of
Smith’s, Adrian Glover, using controversial techniques, had estimated the
number of polychaete species in Area A of DOMES (Deep Ocean Mining
Environmental Study) at between 200 and 500. Thus, there might be
thousands of macrofaunal species in that single area, although nobody had
a good sense of how many species occurred at any of the sites studied in
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