A. (Andreas) Waser

Room: NIOZ
Email: andreas.waser@nioz.nl
Curriculum vitae:
Specialization: Ecology
Project: Predation on littoral mussel beds
DEB tele course

MOSSELWAD - Predation on littoral mussel beds

Mussel beds (Mytulis edulis) are central biogenic structures in the ecosystem of the Wadden Sea. They stabilize the substrate, improve the water quality and they provide important habitats for many (benthic) species. Furthermore, they are an essential food source for aquatic organisms like crustaceans and fishes and for many avian species. In the past, intertidal mussel beds formed a prominent part of the European Wadden Sea.

In the Dutch Wadden Sea though, mussel beds almost disappeared completely on the intertidal mud flats in the early 1990's mainly due to intensive mussel fishery. Since closure of intertidal beds for fishery in 1993, and after strong mussel recruitment in several subsequent years, intertidal mussel bed area has increased again. The most recent estimate is 1400 hectares of intertidal mussel beds. However the recovery has been slower than hoped and mainly occurred in the eastern part of the Dutch Wadden Sea. In the western part only a few hectares of mussel beds have re-established.

It is still not well understood why there is such a big difference in the mussel bed recovery and why the mussel beds have not come back to the western part of the Dutch Wadden Sea. In the West newly developed mussel beds often disappear after one or two years, when the mussels are hardly larger than 30 mm. Only a few make it to a stable mussel bed, where regularly new spat settles next to older cohorts and refreshes the mussel bed.

A possible explanation for the discrepancy between east and west could be based in the difference of predator composition and density and therefore a difference in predation pressure. The main predators for mussels are Oystercatchers, Common Eiders, Herring Gulls and Shore Crabs. While Oystercatchers and Eiders primarily prey on larger mussels, Herring Gulls and Shore Crabs preferably feed on smaller mussels up to around 20 mm. Thus, the latter might be responsible for the failure of the mussel bed recovery in the western part.

This PhD will work in close cooperation with other (MOSSELWAD) PhD's, who will study other (a)biotic factors influencing the development and stability of mussel beds. Fore more information see the mosselwad website.

Internship projects for MSc and BSc students as well as shorter internships are regularly available. If you are interested please contact me for discussing possibilities for a suitable project.

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