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Establishment of the introduced kelp Undaria pinnatifida in Tasmania depends on disturbance to native algal assemblages


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Valentine, JP and Johnson, CR 2003 , 'Establishment of the introduced kelp Undaria pinnatifida in Tasmania depends on disturbance to native algal assemblages' , Journal of Experimental Marine Biology and Ecology, vol. 295, no. 1 , pp. 63-90 , doi: 10.1016/S0022-0981(03)00272-7.

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Despite recent rapid increases in the occurrence of nonindigenous marine organisms in the marine
environment, few studies have critically examined the invasion process for a marine species. Here
we use manipulative experiments to examine processes of invasion for the Asian kelp Undaria
pinnatifida (Harvey) Suringar at two sites on the east coast of Tasmania. Disturbance to reduce cover
of the native algal canopy was found to be critical in the establishment of U. pinnatifida, while the
presence of a stable native algal canopy inhibited invasion. In the first sporophyte growth season
following disturbance of the canopy, U. pinnatifida recruited in high densities (up to 19 plants m 2)
while remaining rare or absent in un-manipulated plots. The timing of disturbance was also
important. U. pinnatifida recruited in higher densities in plots where the native canopy was removed
immediately prior to the sporophyte growth season (winter 2000), compared with plots where the
canopy was removed 6 months earlier during the period of spore release (spring 1999). Removal of
the native canopy also resulted in a significant increase in cover of sediment on the substratum. In the
second year following canopy removal, U. pinnatifida abundance declined significantly, associated
with a substantial recovery of native canopy-forming species. A feature of the recovery of the native
algal canopy was a significant shift in species composition. Species dominant prior to canopy
removal showed little if any signs of recovery. The recovery was instead dominated by canopyforming
species that were either rare or absent in the study areas prior to manipulation of the canopy.

Item Type: Article
Authors/Creators:Valentine, JP and Johnson, CR
Keywords: Invasion process; Introduced macroalgae; Establishment; Disturbance; Canopy removal; Undaria pinnatifida
Journal or Publication Title: Journal of Experimental Marine Biology and Ecology
ISSN: 0022-0981
DOI / ID Number: 10.1016/S0022-0981(03)00272-7
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