Hard substrate fauna on a sublittoral rock revetment in the western Wadden Sea, the Netherlands

Reefs formed by the tube-building polychaete Sabellaria spinulosa are a well-known and widely recognized example of biogenic reef structures that used to occur in the subtidal zone of the Wadden Sea. We derived their optimal habitat requirements and identified a sublittoral rock revetment in the western Wadden Sea as a potential habitat. We mapped the seafloor properties and sampled hard substrate fauna to assess the suitability for Sabellaria. The sublittoral rock revetment lying at water depths of 3.5 m to 14 m below sea level shows a gully slope with a mixture of rocks and sand. The artificial reef has riprap up to 0.5 m in diameter, stretches over 6 km length and has a surface area of 42.5 ha. In total, 80 taxa of fauna were found in five scrape samples of 0.05 m2 each of which 62 were hierarchically unique taxa. Median species richness was 33 and median Shannon-Wiener diversity was 1.70. One individual of the reef-building polychaete Sabellaria spinulosa was found in one of the samples. This is the third record in the Dutch Wadden Sea since 1955. These findings suggest that this sublittoral rock revetment in the western Wadden Sea has suitable habitat conditions for the tube-building polychaete Sabellaria spinulosa