Action: Limit, cease, or prohibit sediment discard during aggregate extraction
Key messagesRead our guidance on Key messages before continuing
- We found no studies that evaluated the effects of limiting, ceasing, or prohibiting sediment discard during aggregate extraction on subtidal benthic invertebrate populations.
‘We found no studies’ means that we have not yet found any studies that have directly evaluated this intervention during our systematic journal and report searches. Therefore, we have no evidence to indicate whether or not the intervention has any desirable or harmful effects.
'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. During aggregate extraction, the unwanted part of the sediment is discarded back into the water or onto the seabed. Consequently, changes occur to the size of sediment particles, which can alter the natural seabed and the invertebrates living on or inside it, but additionally this discarded sediment portion can also directly physically impact invertebrates, for instance through smothering (De Groot 1996). Limiting, ceasing or prohibiting the discard of sediment during aggregate extraction can potentially reduce the amount of alteration to seabed sediment properties, and also avoid smothering of invertebrates. This may facilitate recovery following cessation of activities post-extraction (Cooper 2013). Additional evidence for intervention related to sediment discard during aggregate extraction and other activities are summarised under “Threat: Energy production and mining – Remove discarded sediment material from the seabed following cessation of aggregate extraction”, and “Set limits for change in sediment particle size during rock dump”.
Cooper K.M. (2013) Setting limits for acceptable change in sediment particle size composition: Testing a new approach to managing marine aggregate dredging. Marine Pollution Bulletin, 73, 86–97.
Cooper K., Ware S., Vanstaen K. & Barry J. (2011) Gravel seeding - A suitable technique for restoring the seabed following marine aggregate dredging? Estuarine, Coastal and Shelf Science, 91, 121–132.
De Groot S.J. (1996). The physical impact of marine aggregate extraction in the North Sea. ICES Journal of Marine Science, 53, 1051–1053.