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Algal resource depression by macro-invertebrate herbivores in a chalk stream: An empirical approach

Vincent, Helen Marie (2010)
Ph.D. thesis, University of Birmingham.

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Herbivory is a globally important ecosystem function, occurring in all major biome types; including benthic freshwater habitats. Algal biofilms and their herbivore consumers are therefore important components of stream food webs. However there is relatively little empirical data quantifying the strength of these algal-herbivore interactions, or how these vary with herbivore identity, size, and biofilm physiognomy. Interactions across a diverse herbivore guild were investigated in a chalk stream, using mesocosms to determine the distribution of algal-herbivore interaction strengths. A series of experiments were used to assess: herbivore link strength distribution; context-dependency of interaction strength; the relationship of body size with interaction strength; and the effects of competing grazer species on algal resources. The algal-herbivore sub-web was dominated by weak interactions which concurred with empirical and theoretical evidence, and further supporting web stability theory. Interactions were highly context-dependent, with interaction magnitude and species identity both affected by algal biofilm type. Grazer species identity was important for determining body size relationships. Although competitive effects were apparent, they were not statistically detectable. This research builds on previous investigations of algal grazer interactions and food web structure by emphasizing; the importance of grazing as an ecosystem function, and the diversity of interactions occurring in model systems. The use of experimental mesocosms may be limited in terms of ‘real’ systems, but does provide a valid response of model systems that are both useful and valid tools for assessing community ecology.

Type of Work:Ph.D. thesis.
Supervisor(s):Fudger, Mark E.
School/Faculty:Colleges (2008 onwards) > College of Life & Environmental Sciences
Department:School of Geography, Earth and Environmental Sciences
Subjects:GE Environmental Sciences
Institution:University of Birmingham
ID Code:550
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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