Oschmann, Yvonne (2009) Wie beeinflussen einzelne und kombinierte Umweltstressoren die Verteidigung gegen Konsumenten in Fucus vesiculosus?. (Diploma thesis), Christian-Albrechts-Universität zu Kiel, Kiel, Germany, 68 pp.

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Abstract

Macroalgae are important components of marine coastal ecosystems. Over the last decades there was a decline in macroalgae communities in the Baltic Sea. Herbivory is an important factor affecting macroalgal biomass, abundance and distribution and has an influence on benthic communities. Fucus vesiculosus often dominates shallow regions in the Baltic Sea. Grazing by the isopod Idotea baltica is an important structuring factor in Baltic F. vesiculosus populations. Macroalgae have developed mechanisms against herbivory, i.e. the induction of chemical defense. Recent studies on global climate change predict an increase in sea-surface temperatures and thereby a change in coastal ecosystems. Interactions of abiotic stressors like temperature and the feeding defense of seaweeds have hardly been studied yet. This study shows an effect of temperature on the defense regulation against herbivores in F. vesiculosus. The induced resistance was measured as change in palatability via feeding assays with the consumer I baltica and as change in algal chemistry via high pressure liquid chromatography (HPLC). The phlorotannin content was measured to scrutinize their role in feeding defense. The results showed that rapid jumps in temperature rather than absolute temperatures had a negative effect on defense ability in F. vesiculosus. An indirect effect from high temperatures on algae physiology and Algae-Herbivore-Interactions could not be excluded. The occurrence of an inducible defense and the missing of a correlation between phlorotannin content and feeding preferences of herbivores lead to the assumption, that other unknown secondary metabolites than phlorotannins are responsible for the defense in F. vesiculosus aginst isopods. Assumptions, that saccharides are among such defense metabolites were supported by experiments in this study.

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