Discovery of Sabellaria spinulosa reefs in an intensively fished area of the Dutch Continental Shelf, North Sea

• Published in: Journal of sea research Vol. 144; pp. 85 - 94
• Main Authors: van der Reijden, Karin J., Koop, Leo, O'Flynn, Sarah, Garcia, Silvia, Bos, Oscar, van Sluis, Christiaan, Maaholm, David J., Herman, Peter M.J., Simons, Dick G., Olff, Han, Ysebaert, Tom, Snellen, Mirjam, Govers, Laura L., Rijnsdorp, Adriaan D., Aguilar, Ricardo
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.02.2019; Elsevier BV
• Subjects: Abrasion; Area; Bathymeters; Bathymetry; Biodiversity; Biogenic Reef; Brown Bank; Cancer pagurus; continental shelf; Continental shelves; Crabs; Ecosystem Engineer; Fishing; habitats; Human influences; issues and policy; Man-induced effects; Marine crustaceans; North Sea; Ocean floor; Orientation; Pholis; Pholis gunnellus; Policies; Portunidae; Reefs; Sabellaria; Sabellaria spinulosa; Sand; Sand waves; Sandbanks; Sedimentary structures; Species; Substrates; Swimming; Underwater vehicles; Unmanned vehicles; Valleys; North Sea; Biogenic Reef; Sabellaria spinulosa; North Sea; Ecosystem Engineer; Brown Bank
• DOI: 10.1016/j.seares.2018.11.008
• ISSN: 1385-1101

The tube-building polychaete Sabellaria spinulosa (Ross worm) can form conspicuous biogenic reefs that stabilize the seabed and increase biodiversity by providing a habitat for a multitude of other species. These reefs, however, are assumed to be vulnerable to human-induced physical disturbances of the seabed. In the Greater North Sea, S. spinulosa reefs are recognized to be under threat and worthy of protection. In August 2017, three S. spinulosa reefs with a minimum extent of 1016 m2 were discovered in the Dutch Brown Bank area. This area comprises a large-scale sandbank and adjacent troughs. The reefs were found within the sandbank troughs, which have proven to be subject to high demersal fishing intensities (fished >5 times a year). Detailed bathymetry measurements showed that S. spinulosa reefs were mainly located within valleys of smaller-scaled sand waves, which have a perpendicular orientation compared to the large-scale sandbank structure of the Brown Bank. We hypothesize that the valleys in between sand waves offer suitable substrate for settlement and refuge from abrasion by fishing activities, enabling the S. spinulosa reefs to persist despite high fishing intensities. ROV footage of the reefs showed higher estimates of species abundances on the reefs compared with adjacent habitats, with some species present that are typical for hard substrate (rock gunnel, Pholis gunnellus; edible crab, Cancer pagurus; and velvet swimming crab, Necora puber). The information presented could be used for drafting management policies to protect these reefs, as Contracting Parties of the OSPAR Convention are committed to take measures and protect biodiversity. •Three substantial Sabellaria spinulosa reefs were discovered in the Dutch North Sea.•The reefs were found in the sandbank troughs of the intensively fished Brown Bank.•We observed that the most structured reefs are mainly located in sand wave valleys.•We hypothesize that sand wave valleys create refuges against fishing activities.