Deep Sea Minerals - Vol 2 - Manganese Nodules

3.4

Defining Characteristics of Nodule Biodiversity

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.

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