The Trophic Ecology of Psammechinus miliaris in Scottish Sea Lochs

Student thesis: Doctoral ThesisDoctor of Philosophy (awarded by OU/Aberdeen)


Understanding the trophic relationships between organisms is crucial to understanding ecosystem functioning and as such regular echinoids have been termed keystone through the action of their grazing. Much research has focused on this group’s action as herbivores, but as a group omnivory is common. The aim of this study was to investigate the trophic ecology of the locally super abundant regular echinoid species Psammechinus miliaris within
Scottish sea lochs. To do this the study used manipulative field experiments combined with biochemical analysis of trophic proxies. The manipulative field experiments involved either the hand removal or the caging of P. miliaris to determine the impact the sea urchin grazinghas on benthic community structure. These studies revealed that grazing of P. miliaris can have a major influence on the biomass and structure of the benthic invertebrate
communities. The biochemical analysis of trophic proxies was used to quantify the spatial and temporal variations in the trophic interactions of P. miliaris. These studies focused on the urchin gonad and compared differences in the gonadal somatic indices (reflecting nutritional and reproductive state) with the fatty acid biochemistry and stable isotope ratios of Carbon and Nitrogen. These studies revealed high levels of spatial and temporal heterogeneity in the trophic interactions of P. miliaris and suggested that the populations
exhibited significant levels of omnivory. The combination of these studies showed that P.miliaris plays an important role in structuring benthic invertebrate communities and in the flow of energy through ecosystems and through this, ecosystem functioning.
Date of Award31 May 2006
Original languageEnglish
Awarding Institution
  • The Open University
SupervisorMaeve Kelly (Supervisor) & Dave Barnes (Supervisor)

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