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The invasion and subsequent die-off of Mytilus galloprovincialis in Langebaan Lagoon, South Africa: effects on natural communities
Robinson, T.B.; Griffiths, C.L.; Branch, G.M.; Govender, A. (2007). The invasion and subsequent die-off of Mytilus galloprovincialis in Langebaan Lagoon, South Africa: effects on natural communities. Mar. Biol. (Berl.) 152(2): 225-232. hdl.handle.net/10.1007/s00227-007-0697-x
In: Marine Biology. Springer: Heidelberg; Berlin. ISSN 0025-3162, more
Peer reviewed article  

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Keyword
    Marine

Authors  Top 
  • Robinson, T.B.
  • Griffiths, C.L.
  • Branch, G.M.
  • Govender, A.

Abstract
    The alien mussel Mytilus galloprovincialis invaded sand banks in Langebaan Lagoon on the west coast of South Africa in the mid-1990s. However, by 2001 these beds had completely died off, with only empty shells and anoxic sand remaining. In an effort to prevent the re-settlement of this aggressive invader, all dead mussel shells were then cleared. This study considered the impacts of the invasion and subsequent die-off on natural benthic communities. Community composition differed significantly between non-invaded and invaded areas (ANOSIM, R = 0.685 and P < 0.01) as the physical presence of mussel beds created a new habitat that promoted invasion by indigenous rocky-shore species. This dramatically increased faunal biomass from 1,132.9 g m-2 ± 3,454.7 SD to 53,262.4 g m-2 ± 23,052.6 SD and species richness from 38 to 49 species. Following the die-off of the mussel beds, communities remained significantly different between non-invaded areas and those in which mussel shells remained (ANOSIM, R = 0.663 and P < 0.01). Species richness was significantly greater in non-invaded areas (18 species) than in uncleared areas with remnant shells (four species) (Kruskal–Wallis ANOVA H 2,36 = 10.8964 and P = 0.032), as the previously dominant rocky-shore species became smothered by sediment and the compacted shells formed an impermeable layer excluding sandy-shore burrowing organisms. After the shells were cleared, 50% of the sandy-shore species associated with non-invaded areas returned within 5 months, but community structure still remained significantly different to non-invaded areas (ANOSIM, R = 0.235 and P > 0.05). Invasion thus dramatically altered natural communities and although the subsequent removal of the dead mussel shells appears to have aided recovery, community composition remained different from the pre-invasion state after 5 months.

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