2007, Marine Ecological Surveys Limited, Recoverability of Sabellaria Spinulosa Following Aggregate Extraction, Aggregate Levy Sustainability Fund

Description

Sabellaria spinulosa aggregations have long been a subject of discussion between regulators and marine developers in the UK. The habitat created by these sand grain structures have been widely reported as supporting a unique and diverse fauna that would not otherwise be found on the seabed (UKBAP, 2007). Aggregate dredging and trawling are known to cause physical damage to this habitat although prior to this study there was no information on the longevity and therefore significance of these impacts. There has been some dispute between those who have reported that S.spinulosa aggregations could take many years to recover (UKBAP, 2007) and those who have reported it to exhibit high  recoverability (Jackson & Hiscock, 2006). These disputes and discussions have arisen from the paucity of research into this species and its life history traits. Comparatively extensive research has been carried out on Sabellaria alveolata, an intertidal relative of S.spinulosa and there are many instances in the literature where the differences between the two species is blurred (Vorberg, 2000). This has further complicated the situation with assumptions being made on the basis of these two species having the same or closely mirrored life history traits. The main objective of this investigation was to provide sound scientific information on the recoverability or colonisation potential of Sabellaria spinulosa following aggregate extraction, whilst clarifying some of the life history traits of this animal. In addition to this a detailed investigation into the biodiversity associated with the aggregations was carried out. The quality and physical properties of the aggregations were recorded in order to further our understanding of the environmental conditions most likely to be conducive to colonisation. Hastings Shingle Bank was chosen as the research study site after a number of S.spinulosa aggregations were identified within and adjacent to the active aggregate extraction area. In particular, aggregations had been identified within an area where dredging activities had ceased for less than a year. A comprehensive biological survey was undertaken at the site based on a blocked sampling grid shown opposite. Blocks were positioned in four of the Sabellaria spinulosa aggregations identified in the area as well as in the adjacent substrata and actively dredged part of the licence area. This design facilitated direct comparisons between the different aggregations and the dredged area as well as between each aggregation and the substrata immediately adjacent to them.