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The introduction of artificial hard substrates in an area dominated by a sandy seabed increases habitat available to epifouling organisms. To investigate this, samples were taken on old offshore oil and gas platforms, and data were compared with data of a young wind farm and a natural reef. Depth, sampling date, abundance of Mytilus edulis, Psammechinus miliaris, Metridium dianthus, and the presence of Tubulariidae and substrate (rock or steel) all correlated with species richness. Multivariate analysis showed a large overlap in communities on steel and rock and between the wind farm and platforms. The community changed over a gradient from deep rocks to shallow steel substrate, but no strong community differentiation was observed. Deep steel was more similar to natural rocks than shallow steel. When an artificial reef is intended to be colonized by communities similar to those on a natural reef, its structure should resemble a natural reef as much as possible.

Background: Syllis vittata is present from British Waters to the Mediterranean Sea, Morocco and the Canary Islands and recorded from the South African coast and Indian Ocean.Results and conclusion: In this paper, S. vittata is reported for the first time in the Dutch EEZ.

Harmothoe aspera has been recorded in surveys off the Strait of Georgia, the Skagerrak, and the Barents, Mediterranean and Japanese sea. The recorded depth ranged from circa 48 m to circa 1500 m. This is the first report of H. aspera in the Dutch Exclusive Economic Zone (EEZ), and the first report in a depth range between15 and 20 m.

Reefs play an important role in the distribution of species associated with hard substrates and are of value for biodiversity conservation. High densities of the habitat building annelid Lanice conchilega also increase local biodiversity. This study describes the benthic biodiversity of a rocky reef and its surrounding sand bottom with dense L. conchilega beds in the Borkum Reef Grounds, north of the island of Schiermonnikoog in the Dutch North Sea. A side-scan sonar survey revealed distinct seabed areas with high acoustic reflections, indicating the presence of hard substrate on the sandy seafloor. To ground truth the side-scan sonar data and make an inventory of the biodiversity of the observed habitats, a multi-method sampling approach (box corer, SCUBA airlift sampler and visual transects, drop-down camera) was used. This revealed (1) rocky reefs: a combination of gravel, stones and rocks; (2) individual rocks in a sandy environment; (3) sand with dense L. conchilega beds (>1500ind·m-2) and (4) sand bottom habitat. A total of 193 taxa were found with many unique species per habitat. Species richness was significantly higher on sand when compared to the rocky reef (NB-GLM; p=0.006), caused by the presence of dense L. conchilega beds (Poisson GLM; p<0.001). Including dense L. conchilega beds as an additional habitat showed that these held a higher species richness than the rocky reefs (NB-GLM; p=0.002), while sand without dense L. conchilega beds did not (NB-GLM; p=0.14). Since the rocky reefs were present on a sandy bottom, the local biodiversity more than doubled with the presence of rocky reefs. The nMDS plot clearly separated the sand and rocky reef communities and also showed a clustering of dense L. conchilega beds within the sand samples. Each method detected unique species, demonstrating the value of a multi-method approach compared to e.g. box coring alone. This study identified several species previously unknown to the Borkum Reefs Grounds are, SCOPUS: ar.j, info:eu-repo/semantics/published

[Abstract] Ensis Schumacher, 1817 razor shells occur at both sides of the Atlantic and along the Pacific coasts of tropical west America, Peru, and Chile. Many of them are marketed in various regions. However, the absence of clear autapomorphies in the shell and the sympatric distributions of some species often prevent a correct identification of specimens. As a consequence, populations cannot be properly managed, and edible species are almost always mislabelled along the production chain. In this work, we studied whether the currently accepted Atlantic Ensis morphospecies are different evolutionary lineages, to clarify their taxonomic status and enable molecular identifications through DNA barcoding. For this, we studied 109 specimens sampled at 27 sites, which were identified as belonging to nine of those morphospecies. We analysed nucleotide variation at four nuclear (18S, 5.8S, ITS1, and ITS2) and two mitochondrial (COI and 16S) regions, although the 18S and 5.8S regions were not informative at the species level and were not further considered. The phylogenetic trees and networks obtained supported all morphospecies as separately evolving lineages. Phylogenetic trees recovered Ensis at each side of the Atlantic as reciprocally monophyletic. Remarkably, we confirm the co-occurrence of the morphologically similar E. minor (Chenu, 1843) and E. siliqua (Linné, 1758) along the NW Iberian coast, a fact that has been often overlooked. In South America, a relevant divergence between E. macha (Molina, 1792) individuals from Chile and Argentina was unveiled and suggests incipient speciation. We also confirm the occurrence of the North American species E. directus (Conrad, 1843) as far south as north-eastern Florida. Among the genomic regions analysed, we suggest COI as the most suitable DNA barcode for Atlantic Ensis. Our results will contribute to the conservation and management of Ensis populations and will enable reliable identifications of the edible species, even in