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dc.contributor.supervisorFoggo, Andrew
dc.contributor.authorDeAmicis, Stacey Lynn
dc.contributor.otherSchool of Biological and Marine Sciencesen_US
dc.date.accessioned2012-05-24T08:55:59Z
dc.date.available2012-05-24T08:55:59Z
dc.date.issued2012
dc.date.issued2012
dc.identifier10035800en_US
dc.identifier.urihttp://hdl.handle.net/10026.1/1007
dc.description.abstract

In this thesis I review how Sargassum muticum (Yendo) Fensholt, an invasive alga from Asia, has spread globally due to human activities and describe how this species can affect seagrass ecosystems. Abiotic factors such as nutrient and substratum availability may facilitate the spread of S. muticum into Zostera marina L. meadows, but analyses of seawater nutrients, and sediment particle size and % organic content revealed no significant differences between experimental quadrats in seagrass meadows either with, or without the presence of S. muticum. Phenolic compounds were examined because they form the basis of defensive mechanisms in plants and algae, therefore any change in phenolic content may affect the ability of Z. marina to protect itself from disease, herbivory and invasive species through allelopathic interactions. Results from a four year field study and multiple annual laboratory experiments showed significant reductions (p = 0.034 and p = 0.002, respectively) in the caffeic and tannic acids equivalents content of Z. marina when in the presence of S. muticum. As the abundance of S. muticum increases, other changes in the physiology of Z. marina may occur including variations in growth rates, nutrient partitioning and chlorophyll fluorescence, but data from multiple laboratory experiments illustrated no significant differences in growth. Chlorophyll fluorescence analyses revealed significant differences between treatments with and without S. muticum (p = 0.008), but pairwise comparisons indicated these differences only occurred in 2008 (p < 0.001). Significant differences were also found in nutrient partitioning amongst functional regions of the shoots (p = 0.024), but pairwise comparisons detected these differences between a biomass control treatment (ZZ: Zostera + Zostera) and the ZS (with S. muticum) and ZM (Z. marina on its own at a lower biomass per replicate) treatments (p = 0.013 and p = 0.019, respectively), but not between ZS and ZM. Previous in situ research has found negative effects of S. muticum presence on densities of kelp and other algae. Results from the long-term field study indicated significantly lower mean in situ Z. marina densities within the ZS treatment (p < 0.001). Epibiota found living on the blades of Z. marina provide food for organisms within seagrass ecosystems and also create microhabitats for other species to occupy. Alterations in the abundances of epibiota and microhabitats formed could further modify seagrass ecosystems through shifts in timing of food availability, food preferences and microhabitats created. The long-term field study data revealed significantly lower epibiota abundances within the ZS treatment (p = 0.019), but differences in biomass between treatments were not detected. Changes in the biochemistry, physiology, vegetative physiognomy and epibiota assemblages of Z. marina revealed during experimental manipulations are presented and considered within the context of long-term seagrass survival in light of increasing S. muticum invasion.

en_US
dc.description.sponsorshipJack Kent Cooke Foundationen_US
dc.language.isoenen_US
dc.publisherUniversity of Plymouthen_US
dc.subjectSeagrass vegetative physiognomyen_US
dc.subjectZostera marinaen_US
dc.subjectSargassum muticumen_US
dc.subjectInvasive speciesen_US
dc.subjectPhenolic compoundsen_US
dc.subjectEpibiotaen_US
dc.subjectSeagrassen_US
dc.subjectSeagrass morphometricsen_US
dc.subjectSalcombe-Kingsbridge Estuaryen_US
dc.subjectSeagrass densityen_US
dc.subjectSeagrass growthen_US
dc.titleThe Long-term Effects of Sargassum muticum (Yendo) Fensholt Invasion on Zostera marina L. and its Associated Epibiotaen_US
dc.typeThesis
dc.identifier.doihttp://dx.doi.org/10.24382/4579


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