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have reacted similarly by becoming more numerous in the six months
between the first and second post-impact studies, but they had not done so.
Responding, the biologist suggested that the nematode population
might not have increased within six months because their lifespan was
longer than that. Although the lifespan of deep-sea nematodes was
unknown, shallow-water nematodes lived between 3 and 18 months, or an
average of 9 months. In the deep, larger animals tended to live longer than
their shallow-water counterparts did and the lower temperatures tended to
lengthen life cycles. Thus, 9 months was likely to be a minimum figure for a
deep-sea nematode. In studies of phytodetritus impacts, where bacteria
and forams had shown before-and-after responses, the fact that the
nematode population did not start to climb for almost a year had been
attributed to their longer lifespan. This was speculative but it fit.
Asked whether mining might have the same effect of releasing food,
thereby increasing the nematode population and invalidating any concern
that they might become extinct, the biologist replied that such a response
was possible, though there was also a smothering effect, so he was not
sure. Looking beyond abundance to the ecological impact on diversity,
however, he was willing to bet that, at the peak of abundance in 1992,
diversity had dropped because opportunistic species would have reacted
with a burst. He did not think any predictions could explain the loss of
species, though it was possible that the release of opportunists could knock
the “slow burners” out of the population locally. He cited a study of the top
of a British beach in summer, where nematode abundance and diversity
had fluctuated wildly and competitively in the hot weather before returning
to normal in the autumn. Thus, an abundance rise could mean a diversity
drop.
Schriever noted that an ecological study of this topic was being
published by the Alfred Wegener Institute for Polar and Marine Research 43 ,
based on the taxonomic work of Christian Bussau 44 , who had sorted the
nematodes from the DISCOL study into species.
Disturber device
Another participant asked about the farmer-inspired device
developed for DISCOL, which, he said, seemed to be quite efficient in
leaving no nodules behind and disturbing only 10-15 cm of sediment. He
thought it could be a revolutionary, cheap and simple system for harvesting
nodules.
358 INTERNATIONAL SEABED AUTHORITY