Modification of the physical environment by an <Emphasis Type="Italic">Ecklonia radiata</Emphasis>
(Laminariales) canopy and implications for associated foliose algae |
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Authors: | Email author" target="_blank">Thomas?WernbergEmail author Gary?A?Kendrick Benjamin?D?Toohey |
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Institution: | (1) School of Plant Biology, Botany building MO90, University of Western Australia, Crawley, 6009, WA, Australia;(2) Present address: Centre for Ecosystem Management, Bldg 19, Edith Cowan University, Joondalup, WA, 6027, Australia |
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Abstract: | Macroalgal canopies modify their surrounding environment and thereby influence the structure of associated algal assemblages.
Canopies can modify many factors that can be hard to separate and, consequently, the importance of individual factors often
remains unknown. Experiments were carried out to test the hypotheses that Ecklonia radiata canopies modify light, sediment cover and water motion, and that each of these physical factors separately influence the
assemblage of associated foliose algae. We measured light, sediment cover and water motion across six naturally occurring
E. radiata densities and found a reduction in light and sediment cover as kelp density increased. The outcome for water motion was inconclusive.
We also manipulated each of these three factors, while controlling for the two others, to determine the separate effects of
light, sediment cover and water motion on the assemblage of foliose algae. Reduction in light had a strong effect on the foliose
assemblage, reducing species richness and biomass. Reduction in sediment cover and water motion did not cause separate effects
at the level of the assemblage, but the biomass of individual species of foliose algae indicated both positive and negative
effects. We conclude that E. radiata canopies at Marmion, Western Australia, modify at least two factors of their physical environment, light and sediment cover.
However, only light is modified to an extent where it has effects at the assemblage-level because, in contrast to the effects
of sediment cover and water motion, the direction of responses are consistent among individual species of algae. |
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Keywords: | Canopy effects Canopy density Kelp Light Sediment cover Water motion |
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