standardization of environmental data and information - International ...

on the other hand it turned out that major areas of the CCFZ experienced
resedimentation events on a more routine basis, entombment and burial
might not be such a big issue. A third major impact from nodule mining, of
less importance than the others, was the physical removal by the mining
device of the nodules, surface sediments and animals. The community in
the tracks -- the areas directly mined by the mining head -- would be
severely impacted: macrofauna would be wiped out, while some of the
meiofauna might go through the mining head and survive, but in general the
zone mined would be heavily devastated.
What critical information was needed to predict mining impacts on
both the sediment and the nodule biota? One major open question was the
dose-response function for the benthic community given a single deposition
event. How much sediment redeposition was required to cause a particular
degree of impact, as measured in percentage of mortality? The doseresponse
function was important for extrapolating from small to large
disturbances and for predicting the effect of a plume dispersed at the
seafloor. Another major unknown was the effects of chronic disturbance.
How frequently must modest deposition events -- of less than 1 mm, for
example -- occur for their effects to become chronic, in other words nonindependent?
A one-time deposit of 1 mm of sediment might have a
modest effect on the community, but with repeated monthly deposits of 1
mm at a given site, the effects might become non-independent, producing
much more mortality. The nature of chronic effects was important in
knowing how to manage mining: whether it should be limited to one area for
a while and then be moved 10 or 100 km away in order to minimize
environmental impacts. A third major gap in knowledge concerned the time
scales of community recovery following various intensities of disturbance.
Although there had been some clever mining impact studies, it was still not
known what the recovery times might be from a major mining-like
disturbance in the CCFZ. Some things were known – for example, if
nodules were removed, it would take millions of years before they grew
back, so that the nodule fauna there would require millions of years to
recover, whereas the sediment biota would recover over much shorter
periods.
Smith cited other major open issues: What were the typical
latitudinal and longitudinal ranges of benthic species in the CCFZ and what
were their rates and spatial scales of gene flow? In practical terms, these
questions translated to how large an area could be devastated by mining
without causing species extinctions. In addition, what were the natural
patterns and scales of benthic community variability in space and time?
INTERNATIONAL SEABED AUTHORITY 78