Brittle stars (Echinodermata: Ophiuroidea) in the German Bight (North Sea)—species diversity during the past 130 years

Abstract

In this study, an overview of the current species composition of ophiuroids off Helgoland, German Bight (North Sea) is given. In addition, abundance and distribution of ophiuroids on different types of soft bottom sediments taken by van Veen grab samples around Helgoland were recorded. The literature was reviewed in order to outline the diversity of ophiuroid species over the past 130 years in the inner German Bight. In the historical literature, quantitative references often apply to verbal descriptions and thus make comparisons to modern data and assessment of possible changes in abundance rather subjective.In total, six ophiuroid species were identified off Helgoland: Acrocnida brachiata, Amphiura filiformis, Amphipholis squamata, Ophiothrix fragilis, Ophiura albida and Ophiura ophiura. The species found in this study had also been reported by previous investigators and are regarded as ‘common’ species in the German Bight. Occasional findings in this area refer to Amphiura chiajei, Ophiopholis aculeata, Ophiocten affinis and Ophiura sarsi, which are regarded here as ‘rare’ species. These findings, however, do not indicate sustainable changes in the species diversity over time.Apart from Acrocnida brachiata, a newcomer in the 1970s, findings of the common species mentioned above can be dated back to 1875. Therefore, a fairly stable composition of brittle stars is represented in the inner German Bight during the past 130 years.