The invasion and subsequent die-off of Mytilus galloprovincialis in Langebaan Lagoon, South Africa: Effects on natural communities

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

Research output: Contribution to journalArticle

9 Citations (Scopus)

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.

Original languageEnglish
Pages (from-to)225-232
Number of pages8
JournalMarine Biology
Volume152
Issue number2
DOIs
Publication statusPublished - Aug 2007

ASJC Scopus subject areas

  • Aquatic Science

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