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Effects of algal canopy clearance on plant, fish and macroinvertebrate communities on eastern Tasmanian reefs


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Edgar, GJ, Barrett, NS, Morton, AJ and Samson, C 2004 , 'Effects of algal canopy clearance on plant, fish and macroinvertebrate communities on eastern Tasmanian reefs' , Journal of Marine Biology and Ecology, vol. 312, no. 1 , pp. 67-87 , doi: 10.1016/j.jembe.2004.06.005.

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Changes in assemblages of plants, macroinvertebrates and fishes on three eastern Tasmanian reefs
were monitored over 12 months in replicated control blocks and adjacent 1012-m blocks cleared of
fucoid, laminarian and dictyotalean algae. Removal of canopy-forming plants produced less change
to biotic assemblages than reported in studies elsewhere, with the magnitude of change for fish and
invertebrate taxa lower than variation between sites and comparable to variation between months.
The introduced annual kelp Undaria pinnatifida exhibited the only pronounced response to
canopy removal amongst algal taxa, with a fivefold increase in cleared blocks compared to control
blocks. Marine reserves are suggested to assist reef communities resist invasion by U. pinnatifida,
through an indirect mechanism involving increased predation pressure on sea urchins and reduced
formation of urchin barrens that are amenable to U. pinnatifida propagation.
Large invertebrates were more associated with turfing algae or the reef substratum than the
macroalgal canopy. The herbivorous sea urchin Heliocidaris erythrogramma and abalone Haliotis
ruber showed the strongest response to clearing amongst common macroinvertebrate species, with a
halving of population numbers. Observed densities of the common monacanthid fish Acanthaluteres
vittiger also declined by about 50%. The relatively high level of resistance shown by eastern Tasmanian reef biota to patch disturbance was attributed largely to high diversity and biomass of
turfing macroalgae damping effects of canopy clearance.

Item Type: Article
Authors/Creators:Edgar, GJ and Barrett, NS and Morton, AJ and Samson, C
Journal or Publication Title: Journal of Marine Biology and Ecology
DOI / ID Number: 10.1016/j.jembe.2004.06.005
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