Occurrence, stability, and associated species of subtidal mussel beds in the North Frisian Wadden Sea (German North Sea Coast)
Ricklefs, K.; Büttger, H.; Asmus, H. (2020). Occurrence, stability, and associated species of subtidal mussel beds in the North Frisian Wadden Sea (German North Sea Coast). Est., Coast. and Shelf Sci. 233: 106549. https://dx.doi.org/10.1016/j.ecss.2019.106549 In: Estuarine, Coastal and Shelf Science. Academic Press: London; New York. ISSN 0272-7714; e-ISSN 1096-0015, more |  |
| Authors | | Top | - Ricklefs, K.
- Büttger, H.
- Asmus, H., more
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| Abstract | According to historical literature, subtidal blue mussel (Mytilus edulis) beds were relatively widespread in the North Frisian Wadden Sea in the first decades of the 20th century. However, natural subtidal mussel beds subsequently suffered severe losses, partly due to natural causes but also as a consequence of uncontrolled fishing. Especially after the Second World War blue mussels could only be reliably found at a few natural locations by the 2000s. Notably, past sampling techniques using grabs and dredges mean that our knowledge of the areal dimensions and characters of these blue mussel habitats remained limited. Since 2009 broad side scan sonar surveys have been applied to map sediments and to detect subtidal mussel beds or their potential habitats. Apart from several locations with hints of mussels, only two mussel beds were recognized as biogenic reefs according to the EU Habitats Directive. These beds have been monitored annually since 2012. Although the beds have remained relatively stable in terms of area, both beds showed an increasing degradation of their accuracy of topographical discrimination from the surrounding seabed over the years. In line with this degradation, we observed a decline in blue mussel abundance and a strong increase in the dominance of the Pacific oyster (Magallana gigas). However, the final year of the investigation (2018) was characterised by a strong decline in both Mytilus and Magallana populations at both sites. |
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