Date of Award

2010

Degree Type

Thesis

Degree Name

Doctor of Philosophy

Faculty

Faculty of Computing, Health and Science

Abstract

The ongoing threat of seagrass loss from reduced light availability, coupled with our lack of knowledge of associated trophic responses has motivated this characterization of the flow-on effects of light reductions to Amphibolis griffithii seagrass fauna. Recently, field manipulations of varying light reductions, induced disturbances in a A. griffithii seagrass meadow that have been shown to effect potential food resources and the structural complexity of seagrass habitats for macroinvertebrates. This offered the opportunity to assess the flow-on effects to seagrass for fauna, a topic that has seldom been examined. This study investigated the effects of different light reduction intensity (high: ~92% reduction; moderate: ~84% reduction), duration (3, 6 and 9 mo) and timing (post-winter and post-summer) on the density, biomass and community composition of macroinvertebrate epifauna within an A. griffithii seagrass ecosystem (Western Australia). Shade structures, placed within a healthy A. griffithii meadow, were used to create the light reduction treatments. Following shading, there were significant interactions between all three light reduction factors, and generally there was decline in the density and biomass of fauna (between 38% and 89% in density) and the number of families with increasing duration and intensity of light reduction (between 11 and 53% fewer families in light reduction treatments). There was also an effect of time, with taxa abundance and family composition Post-summer differing to Post-winter.

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