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Marine Ecology Progress Series

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MEPS 381:83-97 (2009)  -  DOI:

Consequences of light reduction for anti-herbivore defense and bioactivity against mussels in four seaweed species from northern-central Chile

Christian Pansch1,*, Osvaldo Cerda2, Mark Lenz1, Martin Wahl1, Martin Thiel2,3

1Leibniz Institute of Marine Sciences at the University of Kiel, IFM-GEOMAR, Marine Ecology, Düsternbrooker Weg 20,
24105 Kiel, Germany
2Departamento de Biología Marina, Facultad de Ciencias del Mar, Universidad Católica del Norte, Larrondo 1281, Coquimbo, Chile
3Centro de Estudios Avancados en Zonas Aridas, CEAZA, Coquimbo, Chile

ABSTRACT: It is widely assumed that the production of secondary metabolites against grazing and fouling is costly for seaweeds in terms of metabolic energy and should therefore be reduced under conditions of resource limitation. Here we tested the hypothesis that anti-herbivore defenses and bioactivity against mussels in 4 brown seaweeds from northern-central Chile will be reduced when light is limited. In a 2 wk experiment, seaweeds were kept under different low-light conditions (~76 to 99% reduction of ambient sunlight) and grazing situations. Subsequently, we tested their anti-herbivore defense against a common amphipod grazer in feeding assays with living algal tissue and reconstituted food pellets. A standard test employing the production of byssus threads by mussels was furthermore used as an indicator for deterrents in crude algal extracts. All investigated seaweeds showed decreased growth under the stepwise light reduction. Lessonia nigrescens exhibited reduced defense ability under severe low-light conditions when living tissue was offered to the amphipod, probably caused by changes in the tissue structure or in nutritional traits. In Dictyota kunthii, L. trabeculata and Macrocystis integrifolia this effect was absent. None of the investigated seaweeds showed a clear effect of light reduction on chemically mediated defenses against the mesograzer and there was no effect of light limitation on the bioactivity against mussels. Thus, against general assumptions, chemical defense in the investigated seaweeds does not appear to be reduced under severe resource limitation. Results suggest that seaweeds may use different strategies of energy allocation to cope with low-light conditions.

KEY WORDS: Seaweeds · Macroalgae · Chemical defense · Light limitation · Herbivores · Fouling

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Cite this article as: Pansch C, Cerda O, Lenz M, Wahl M, Thiel M (2009) Consequences of light reduction for anti-herbivore defense and bioactivity against mussels in four seaweed species from northern-central Chile. Mar Ecol Prog Ser 381:83-97.

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