standardization of environmental data and information - International ...

Another participant observed that his experience in diving with a
submersible in the Central Pacific Ocean had made clear that the diversity
of landscape was probably an important factor in the distribution of
biotypes. Though there had been no opportunity to take measurements at
that time, it looked as if he had been in the middle of the Alps, with flats
that changed from place to place according to the presence of absence of
nodules, bottoms and tops of cliffs, and so on. Because of this variety,
much information would be lost if sampling took place without knowing
where the samples had been taken.
Agreeing, Rex stressed that the wonderful diversity of environments,
including chemosynthetic ones, corresponded to changes in biodiversity in
the deep sea. Just a few years ago, these had been unimaginable, and
even today most of the deep sea was still unexplored. As he had said when
talking about the relationship between local and regional diversity, for many
of the species that shared landscape habitats, their presence in one habitat
might have important implications for their continued survival in others as
well.
Depth comparisons and relationships
Asked about the comparative amounts of biomass at the surface
and in the deep sea, Rex said biomass decreased exponentially with depth.
One rule of thumb was that it dropped by about an order of magnitude every
thousand metres, though with large variations from place to place. On this
point, Craig R. Smith clarified that that was true when comparing shallowwater
sediment to deep-sea sediment. However, in the water column of the
CCFZ, there was more microbial biomass in the top metre of sediment at
the bottom of the ocean than in the whole water column above.
A participant asked about relationships between species at different
levels of the ocean and how those higher up would be affected by extinction
below. Rex responded that there was a complete change of fauna from the
upper bathyal zone -- at about 500 m -- to the abyss, though the depth
ranges of some abyssal species varied in different parts of the ocean.
Compared to the abyssal depths, the bathyal zone was a minute part of the
ocean floor, just a little ribbon around the margin of the seas. The high
species turnover with depth implied a long process during which tolerance
to abyssal conditions had evolved. Thus, it should not be thought that, if
the abyssal fauna were extirpated, the bathyal fauna would provide a
reservoir of species to repopulate it. There had been a shift in thinking to
the effect that the deep sea was an integral part of the biosphere.
318 INTERNATIONAL SEABED AUTHORITY