Impacts of SMS mining are predicted to occur across all marine environments (benthic, bathypelagic, mesopelagic and epipelagic) ranging from site to regional scale over both short and prolonged durations (summarised in Table 2) (Gwyther, 2008b). Within the benthic environment alone, there is a range of habitats including both hard and soft substrata with different communities residing on or in each. The benthic organisms also span a range of sizes, including the microfauna (<63 μm), meiofauna, (63–500 μm), macrofauna (500 μm–5 cm) and megafauna (>5 cm), with different ecological characteristics, including the nature and extent of dispersal, mobility,
feeding strategies and trophic interactions. Such a suite of habitats, faunal assemblages and ecologies this website means that the response of benthic organisms to SMS mining will vary widely, complicating any attempt to generalise the identification and mitigation of impacts. The nature and the scale of those impacts (both spatial and temporal) are also likely to be different at different deposits. Table 2 summarises the only site-specific impact assessment currently available (see Gwyther (2008b) for full assessment), but different sites may have additional impacts to consider. The impacts from SMS mining will also vary
with the methods and equipment used. For example, the predicted impacts from the proposed SMS mining methods Dinaciclib ic50 of the Japan Deep Sea Technology Association (DESTA) are more varied with a greater risk of smothering (Fukushima and Okamatsu, 2010) than those for Solwara 1 outlined in Table 2. Modelling studies of the dispersal of unconsolidated sediment discharge at Solwara 1 indicated that increased sedimentation thicknesses of up to 500 mm may occur within 1 km of the discharge site (Gwyther, 2008b). Some particulate material
may extend up to 10 km from the site, but settle at lower than natural rates. Existing sediment thicknesses at and around Solwara 1 are 6 m deep in places (Gwyther, 2008b). Return water plumes may extend 5–10 km Mirabegron from the mining site, with maximum deposit thickness of 0.1 mm and rates of settling less than existing deep-sea sedimentation rates (Gwyther, 2008b). Sediment and water column plumes will disperse with distance, and hence “downstream” effects will be less than at the site where they are formed. This dilution will mean there is a gradient of impact, with effects lessening with distance away from the mining site. The potential distance and depth of sedimentation effects will vary among sites, and will need to be assessed in any prospective mining area. With regards to the toxicity of these plumes, it is thought that high concentrations of heavy metals will pose minimal risk to the fauna adapted to active SMS deposits (Gwyther, 2008b).