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the plume, could be a large area with several replicates. If there were three
stations in each site, there would be nine stations in all, to be sampled through
time. One possibility was to sample four times before mining and four times
after. This might be done with varying periodicity -- every year, or at intervals of
one, two, four and eight years. Those who did not want to sample for eight
years before starting to mine could reduce this to a shorter period or take
fewer samples, as he would explain shortly. If the design called for three boxcore
samplings at each of three stations in three areas, repeated eight times,
216 box cores would be required over the eight-year period. That would be the
level of replication in space and time required for an adequate test. Testing at
multiple plume sites would increase the amount of replication.
It would be hard to select locations for the control sites. Selection
would depend on the scales of the organisms and of the plume. A decision
would have to be taken soon after an area was chosen for exploration because
the stations would have to be sited before mining began, taking account of the
temporal scales required for testing. A power analysis should be done to
ensure that an impact could be detected with the minimum amount of
replication that he was suggesting. He also suggested that an epibenthic sled
sample be taken at each of the stations at least once during the study, to give
some idea of how well the communities were being sampled and to provide
information on the total community, including things that the box cores might
miss. This would also make it possible to do genetic studies if necessary.
Epibenthic sleds were important because their large samples, more qualitative
than quantitative, were necessary to answer questions about population
genetics and gene pools.
His sampling design would end up with 27 box cores replicated through
eight years. This would leave the communities well characterised for an
abyssal site, better than in many other studies, at all nine stations.
Information would be obtained about spatial variation on a variety of scales,
because calculations could be made at different scales. Natural temporal
variability over a period of up to eight years could also be measured from the
samples. An estimate of the recovery rate would be gained from the impacted
site, i.e. the temporal series of the recovery rate. Something would be learned
about the interaction between space and time, that is, how the samples
changed relative to one another over time. Finally, it would be possible to test
in a rigorous way whether there had been an impact.
One positive aspect of the course he had outlined was that it supplied
basic information about the organisms at the same time that it was testing for
an impact. With other strategies, a lot of work would still be needed to quantify
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