MANGANESE NODULES
34
Defining Characteristics of
Nodule Biodiversity
3.4
The faunal communities associated with nodules have been de-
scribed in detail in the preceding section on nodule habitats
and ecosystems. There are several key characteristics to be
considered specifically for this environment when evaluating
potential impacts. These considerations, and others, are sum-
marised below.
Sea-floor habitats in abyssal nodule regions are believed to be
physically stable, especially when compared to the more dy-
namic physical setting of actively venting sea-floor massive sul-
phide deposits. Animals associated with nodules are unlikely to
be well adapted to cope with disturbance.
The faunal composition differs between the nodules and the
surrounding and intervening soft sediment. The biological char-
acteristics of nodule and non-nodule communities differ, which
needs to be considered when evaluating effectiveness of man-
agement options. Abundance and density of epifauna (animals
living on the surface of the sea-floor) in abyssal habitats is gen-
erally low, whereas infauna (animals living within the sediment)
can be highly diverse and abundant.
Many of the abyssal animals are surface-deposit feeders, relying
upon recently-settled particulate matter from the water column,
or suspension feeders that trap particles before they settle on the
sea-floor. Sedimentation rates and particulate organic carbon
flux are therefore important drivers of abyssal ecosystems.
Recolonization rates of fauna are low, and hence recovery from
impacts is expected to be slow. It is probably not practical to
expect visible recolonization of animals within the tenure of a
mining licence.
