Extract aggregates from a vessel that is moving rather than static

Background information and definitions

'Aggregates’ is the collective term for sand, gravel and crushed rock. They are used as raw materials for the construction industry as well as for beach replenishment schemes. Aggregate extraction can impact subtidal benthic invertebrates through physical removal, loss and alteration of seabed and habitat, and direct physical damage from the machinery used (De Groot 1996). Two methods are commonly practised: anchor suction hopper dredging, a static type of extraction (De Groot 1996), and trailer suction hopper dredging which takes place from a moving vessel (Birchenough et al. 2010; Boyd & Rees 2003). In some areas, such as in the UK, both methods are used (Boyd & Rees 2003). Although both methods cause severe disturbance in seabed invertebrate communities (Desprez 2000, Sardá et al. 2000), the differences between dredged and surrounding undredged areas are more significant after static dredging (Boyd & Rees 2003). Trailer dredging is thought to reduce the intensity, and therefore the impact, of dredging in any one area by leaving small pockets of areas unaffected and from which recolonization and recovery may occur (Szymelfenig et al. 2006). Evidence for related interventions is summarised under “Threat: Energy production and mining – Mining and quarrying”.

_{Birchenough S.N., Boyd S.E., Vanstaen K., Coggan R.A. & Limpenny D.S. (2010) Mapping an aggregate extraction site off the Eastern English Channel: a methodology in support of monitoring and management. Estuarine, Coastal and Shelf Science, 87, 420–430.}

_{Boyd S.E. & Rees H.L. (2003) An examination of the spatial scale of impact on the marine benthos arising from marine aggregate extraction in the central English Channel. Estuarine, Coastal and Shelf Science, 57, 1–16.}

_{De Groot S.J. (1996) The physical impact of marine aggregate extraction in the North Sea. ICES Journal of Marine Science, 53, 1051–1053.}

_{Desprez M. (2000) Physical and biological impact of marine aggregate extraction along the French coast of the Eastern English Channel: short-and long-term post-dredging restoration. ICES Journal of Marine Science, 57, 1428–1438.}

_{Sardá R., Pinedo S., Gremare A. & Taboada S. (2000) Changes in the dynamics of shallow sandy-bottom assemblages due to sand extraction in the Catalan Western Mediterranean Sea. ICES Journal of Marine Science, 57, 1446–1453.}

_{Szymelfenig M., Kotwicki L. & Graca B. (2006) Benthic re-colonization in post-dredging pits in the Puck Bay (Southern Baltic Sea). Estuarine, Coastal and Shelf Science, 68, 489–498.}