Facilitative effects of introduced Pacific oysters on native macroalgae are limited by a secondary invader, the seaweed Sargassum muticum
Lang, A.C.; Buschbaum, C. (2010). Facilitative effects of introduced Pacific oysters on native macroalgae are limited by a secondary invader, the seaweed Sargassum muticum. J. Sea Res. 63(2): 119-128. https://dx.doi.org/10.1016/j.seares.2009.11.002
In: Journal of Sea Research. Elsevier/Netherlands Institute for Sea Research: Amsterdam; Den Burg. ISSN 1385-1101; e-ISSN 1873-1414, more
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| Keywords |
Characteristics > Stand characteristics > Canopy
Characteristics > Stand characteristics > Understorey
Epibenthos
Taxa > Species > Introduced species
Sargassum muticum (Yendo) Fensholt, 1955 [WoRMS]
Marine/Coastal |
| Authors | | Top |
- Lang, A.C.
- Buschbaum, C., more
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| Abstract |
Introduced habitat-providing organisms such as epibenthic bivalves may facilitate the invasion and expansion of further non-native species which may modify the effects of the primary invader on the nativesystem. In the sedimentary intertidal Wadden Sea (south-eastern North Sea) introduced Pacific oysters (Crassostrea gigas) have overgrown native blue mussel beds (Mytilus edulis). These oyster beds are now providing the major attachment substratum for macroalgae. Recently, oysters have expanded their distribution into the shallow subtidal zone of the Wadden Sea, and there support a rich associated species community including the Japanese seaweed Sargassum muticum, which has been presumably introduced together with the oysters. With a block designed field experiment, we explored the effects of S. muticum on the associated community of soft-bottom C. gigas beds in the shallow subtidal. Replicated oyster plots of1 m2 were arranged with a density of 0, 7, 15 or 45 S. muticum m−2, respectively. We found no effects of different S. muticum densities on associated epi- and endobenthic community compositions associated to the oyster plots. However, the overall coverage of sessile organisms settling on the oyster shells was significantly reduced at high S. muticum densities. The occurrence of abundant native macro-algal species such as Polysiphonia nigrescens, Antithamnion plumula and Elachista fucicola decreased with increasing S. muticum densities. Sessile invertebrates, by contrast, were only marginally affected and we found no effects of S. muticum canopy on diversity and abundance of endofauna organisms. We conclude that increasing densities of S. muticum on C. gigas beds in the shallow subtidal zone of the Wadden Sea limit the occurrence of native macroalgae which otherwise would benefit from the additional hard substratum provided by the oysters. Thus, a secondary invader may abolish the effects of the primary invader for native species by occupying the new formed niche. |
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