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Mesoscale dispersal of the introduced kelp Undaria pinnatifida attached to unstable substrata


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Sliwa, C, Johnson, CR and Hewitt, CL 2006 , 'Mesoscale dispersal of the introduced kelp Undaria pinnatifida attached to unstable substrata' , Botanica Marina, vol. 49, no. 5-6 , pp. 396-405 , doi: 10.1515/BOT.2006.051.

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In areas of Tasmania and New Zealand, the introduced
Japanese alga, Undaria pinnatifida, grows attached to
unstable substrata such as small cobbles and shells.
Observations suggest these algae may disperse by saltation
(i.e., a series of jumps) while attached to their substratum.
A predictive model was developed to estimate
the dispersal rate of U. pinnatifida by this mechanism,
depending on drag force (as a function of lamina surface
area and water velocity), the buoyant weight of the
attached substratum and the depth at which the alga
was located. The model was parameterised based on
empirical measurements of 89 tagged thalli in the field,
and estimates of drag on different sized laminae determined
from experiments in a large flume tank. Empirical
observations and model predictions suggest that under
typical conditions at moderately exposed sites, dispersal
via this mechanism is likely to be of the order of at least
10[to the power of]1 - 10[to the power of]2 m per year. When compared to the likely dispersal
of spores from the parent (approx 10 [to the power of]1 m per year), and
the likely dispersal of fertile drift thalli (approx 10[to the power of]4 m per
year), we suggest that algae on unstable substrata may
provide a mechanism for intermediate dispersal over
moderate distances, providing sufficient spore density to
ensure high fertilisation success. This is likely to enhance
the rate of spread of U. pinnatifida in circumstances
where habitat suitable for establishment is available.

Item Type: Article
Authors/Creators:Sliwa, C and Johnson, CR and Hewitt, CL
Keywords: dispersal; invasion biology; macroalga; Undaria pinnatifida; unstable substrata
Journal or Publication Title: Botanica Marina
DOI / ID Number: 10.1515/BOT.2006.051
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