standardization of environmental data and information - International ...

Stuart and Rex 22 have shown that local diversity of deep-sea
molluscs is positively correlated with both diversity of the regional species
pool and the proportion of species that have dispersing larvae. This
suggests that local community diversity is maintained, in part, by continued
dispersal from the regional pool. In other words, local community structure
is related to regional-scale processes. Anthropogenic impacts will vary
depending on regional diversity, the geographic distribution of species and
the life-history characteristics of the regional fauna. The interaction of local
and regional processes implies that mining in one part of a region may have
broad consequences for communities elsewhere in the region that are not
directly affected by mining.
1.4. Landscape Level
Once thought to be a relatively uniform environment throughout, the
deep sea is now known to have a very high diversity of habitats and
topographic complexity 23 . The deep-sea fauna are zoned with depth and
show marked changes in diversity and composition with topographic
features, current regimes, sediments and oxygen-minimum zones 24 . A great
variety of chemosynthetic communities also exist 25 . It is clear that many
soft-sediment, hard-substrate and chemosynthetic communities share
some proportion of their faunas. However, the extent to which this is true
and the importance of dispersal among habitats in the persistence of
species remain unclear.
2. Abyssal Communities
Much less is known about community structure at abyssal depths
far at sea, where mining is targeted, than at bathyal depths along
continental margins. Standing stock declines exponentially with depth,
reaching levels in the macrofauna on the order of 1 gram/m 2 and 100
individuals/m 2 below 4000 m 26 . Diversity, while somewhat lower than at
bathyal depths in terms of the number of species per unit area at local
scales, appears to remain fairly high. The circumstances of very low animal
abundance and high diversity make it particularly difficult to detect spatial
changes in community structure without taking a large number of box-core
samples 27 . Comparisons between reserve and disturbed areas need to be
carefully controlled in the sampling design, since abyssal communities now
appear to experience natural cycles of food supply and demand on decadal
time scales 28 , which could compromise a simple before-and-after sampling
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