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Marine Ecology Progress Series

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MEPS 283:113-125 (2004)  -  doi:10.3354/meps283113

Effect of mesograzers and nutrient levels on induction of defenses in several Brazilian macroalgae

Kerstin Weidner1, Bruno G. Lages2, Bernardo A. P. da Gama2, Markus Molis3,4,*, Martin Wahl3, Renato C. Pereira2

1Interdisciplinary Ecology Centre, Technical University Bergakademie Freiberg, Leipziger Straße 29, 09599 Freiberg, Germany 2Departamento de Biologia Marinha, Instituto de Biologia, Universidade Federal Fluminense, CP 100.644, CEP 24001-970 Niterói, Rio de Janeiro, Brazil 3Leibniz Institute of Marine Sciences, Marine Ecology/Marine Zoology, Düsternbrooker Weg 20, 24105 Kiel, Germany 4Present address: Marine Biological Station Helgoland, Foundation Alfred Wegener Institute for Polar and Marine Research,Kurpromenade 201, 27498 Helgoland, Germany
*Corresponding author. Email:

ABSTRACT: Herbivory can greatly modify benthic community structure by affecting the distribution of algal species. To deter herbivores, algae have developed several mechanisms, including the induction of chemical and morphological defenses, which may be influenced by nutrient availability. We tested 4 red (Chondrophycus flagellifera, Cryptonemia seminervis, Osmundaria obtusiloba, Pterocladiella capillacea), 4 brown (Dictyota menstrualis, Lobophora variegata, Sargassum vulgare, Stypopodium zonale), and 1 green (Codium decorticatum) algae for inducible defenses following exposure to direct consumption by an amphipod community dominated by Elasmopus brasiliensis. In addition, the effects of water-borne cues from nearby grazed conspecifics and non-grazing consumers on the induction of defenses were examined in C. decorticatum under natural and enhanced (200% natural) nutrient levels. Induction of defense was assessed in choice-feeding assays, using live algae or artificial food containing non-polar extracts of amphipod-exposed (treated) and non-exposed (control) algae. Palatability levels, estimated as the relative difference in wet mass due to consumption in feeding assays between grazer-exposed and control plants, declined significantly in 3 species after the acclimatization period. Tissue from the directly consumed red alga P. capillacea (live alga) was significantly less palatable than tissue from the control plants. Likewise, a significant effect was observed in the brown alga L. variegata. Similar, although not statistically significant, trends were observed in 6 other species. For the green alga C. decorticatum, nutrient enrichment did not affect induction of defenses by herbivores, yet unfertilized plants were more palatable than fertilized conspecifics.

KEY WORDS: Plant-animal interaction · Tropical seaweeds · Mesograzer · Nutrient enrichment · Feeding preference

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