Biological Invasions

, 12:15

Recently established Crassostrea-reefs versus native Mytilus-beds: differences in ecosystem engineering affects the macrofaunal communities (Wadden Sea of Lower Saxony, southern German Bight)


    • Department for Marine ResearchResearch Institute Senckenberg
  • Achim Wehrmann
    • Department for Marine ResearchResearch Institute Senckenberg
  • Ingrid Kröncke
    • Department for Marine ResearchResearch Institute Senckenberg
Original Paper

DOI: 10.1007/s10530-009-9425-4

Cite this article as:
Markert, A., Wehrmann, A. & Kröncke, I. Biol Invasions (2010) 12: 15. doi:10.1007/s10530-009-9425-4


Since 1998 the non-indigenous Pacific oyster Crassostrea gigas (Thunberg 1793) has been invading the Wadden Sea of Lower Saxony, southern German Bight. C. gigas settles predominantly on intertidal Mytilus-beds (M. edulis L.) and subsequently create rigid reef-like structures. Both bivalve species are ecosystem engineers in sedimentary tidal flats. They provide hard substrate for sessile species, mobile organisms find refuge within the habitat matrix of dense suspension feeders, and biodeposits enrich the sediments with organic matter. The transformation of Mytilus-beds into Crassostrea-reefs gives rise to the question whether the invader may affect the native community. We investigated two parts of a changing bivalve bed in the backbarrier area of the island of Juist in March 2005. One part was still dominated by M. edulis whereas the other part was already densely colonized by C. gigas. Crassostrea-reefs compensate for the conceivable loss of Mytilus-beds in the intertidal of the Wadden Sea by replacing the ecological function of M. edulis. There was no indication of a suppression of indigenous species. This even applied to M. edulis, which persisted at the site invaded by C. gigas. The associated macrofaunal community showed increased species richness, abundance, biomass, and diversity in the Crassostrea-reef. The latter particularly favored sessile species like anthozoans, hydrozoans, and barnacles. Higher abundance and biomass for vagile epizoic species like the shore crab Carcinus maenas and the periwinkle Littorina littorea also occurred among oysters. Abundance of deposit feeding oligochaetes was enhanced by oysters as well. More opportunistic, facultative filter-feeding polychaetes occurred in the Crassostrea-reef.


BioinvasionBiozoenosisCrassostrea gigasDiversityEcosystem engineeringMacrofaunaMytilus edulisNeozoaNorth Sea

Copyright information

© Springer Science+Business Media B.V. 2009