Effects of allelopathic compounds produced by native and invasive marine macroalgae on the associated communities

Lenzo, Denise (2023) Effects of allelopathic compounds produced by native and invasive marine macroalgae on the associated communities, [Dissertation thesis], Alma Mater Studiorum Università di Bologna. Dottorato di ricerca in Scienze della terra, della vita e dell'ambiente, 35 Ciclo.
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In this study, the production of bioactive secondary metabolites called "allelochemicals" by algae has been investigated, specifically focusing on polyunsaturated aldehydes (PUAs). PUAs are known to have adverse effects on planktonic grazers and on phytoplankton; however, their effect on benthic communities has been poorly studied. Macroalgae are ecosystem engineers that play an important role in the structure of the habitat and associated communities, presenting a great variability in their morphology and structural complexity, which is a primary factor in the structuring of associated communities. In recent decades, it has been seen how the introduction of invasive species can modify the benthic habitat structure, causing cascading effects on the trophic chain. The thesis includes several field and laboratory studies. Field studies examined aldehyde production by native and invasive macroalgal species (Sargassum muticum, in the Adriatic Sea, and Rugulopterix okamurae in the Strait of Gibraltar), their structural complexity, together with their associated phyto and meiobenthos. Two laboratory studies were conducted. The first one, based on microcosms experiments, evaluated the effect of PUA (produced by the diatom Skeletonema marinoi, or as decadienal analytical standard) on meiofauna. The second one evaluated the inhibitory effect of dilkamural, an allelopathic compound isolated from R. okamurae, on unicellular phototrophs. Our results showed that PUAs produced by macroalgae were species-specific and had a significant impact on the benthic community. The morphology of macroalgae was an important factor in shaping associated communities, particularly for microphytobenthos. Invasive species, such as S. muticum and R. okamurae, could reduce the biodiversity of native benthic communities and simplify the habitat. Dilkamural was hypothesized to be an allelochemical defense, and laboratory toxicity tests confirmed this hypothesis. Overall, this thesis sheds light on the importance of allelochemicals and macroalgal structural complexity in the benthic environment and highlights the potential impact of invasive species.

Tipologia del documento
Tesi di dottorato
Lenzo, Denise
Dottorato di ricerca
Settore disciplinare
Settore concorsuale
Parole chiave
Brown macroalgae; PUAs; microalgae; meiofauna; harpacticoid copepods; chemical ecology; macroalgal structural complexity; microphytobenthos; non-indigenous species;diterpenoids; growth inhibition assay; Synechococcus sp.; Phaeodactylum tricornutum; Cyclotella cryptica
Data di discussione
15 Giugno 2023

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