standardization of environmental data and information - International ...

the CCFZ. Without understanding levels of biodiversity, it was difficult to
predict the potential for species extinctions.
Low physical energy
The deep sea in most regions was also regarded as having low
levels of physical energy. With slight currents producing low amounts of
sediment transport, most of the structure was considered to be formed
either by animals -- biogenic structures such as worm tubes -- or by
manganese nodules. When pairs of time-lapse photographs were taken
between 124 and 202 days apart at three sites within the nodule province,
the earlier and later photos in each pair looked much alike. Sediment
structures had changed little, suggesting that on roughly one-year time
scales there was little remobilisation of sediment and that biogenic
structure was a primary source of animal habitat.
Photographs from another site in the nodule province, of a large
biogenic structure that was probably a worm mound, showed nodules sitting
high up on the sediment – evidence viewed to mean that the animals rarely
experienced resuspension events. As nodules grew at rates of roughly 1
millimetre per million years and were denser than the sediment, if
resuspension events were occurring one would expect the nodules to be
buried. Nevertheless, the concept of low energy and high physical stability
of the seafloor in the nodule provinces was somewhat controversial at this
point, because some current meter and sedimentological data, particularly
from the eastern CCFZ, suggested that, at least on geological time scales
and possibly even annually, resuspension and sediment transport events
might be occurring.
The issue was important because, if the community was stable and
never experienced resuspension over long periods -- years, decades or
centuries -- then resuspension resulting from mining was likely to have
significant ecological impact. On the other hand, if resuspension and
redeposition were routine in major areas of the nodule province, the
animals in those habitats were likely to be pre-adapted to dealing with some
of the disturbances that might result from mining. In summary, most deepsea
biologists viewed the CCFZ as stable but there might be some recent
evidence to the contrary in portions of the nodule province.
73 INTERNATIONAL SEABED AUTHORITY