University of Tasmania
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From temperate to tropical seas : drivers of variation in reef-associated epifaunal invertebrate communities

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posted on 2023-05-28, 11:56 authored by Kate FraserKate Fraser
Globally, shallow reef ecosystems are undergoing dramatic changes, largely due to unprecedented climate change and exacerbated by local anthropogenic drivers. These changes are generally mediated by habitat transformation, which has critical implications for ecological communities and food web dynamics, often beginning at basal trophic levels with flow-on effects throughout food webs. Small mobile invertebrates ('epifauna') inhabiting the surfaces of structurally diverse reef habitats are prolific and ubiquitous on reefs worldwide, representing an essential basal trophic group that fuels much of shallow reef food webs. This thesis examines the interactive influences of local and broad-scale drivers on epifaunal community composition, size structure and productivity on shallow reefs along a steep eastern Australian climatic gradient of 28.6¬∞ with mean annual temperature range of ~13¬∞C. The overarching aim of this research is to understand how epifaunal communities vary across different reef habitat types, locations and latitudes, and environmental and ecological gradients, to better understand the broader ecological implications of ocean warming and local anthropogenic impacts on reef food webs. Habitat is identified as the most important correlate of variation in epifaunal assemblages regardless of latitude or the metric used to quantify assemblages. Macroalgae, live coral and turfing algae represent three habitat extremes in terms of the taxonomic composition of epifaunal assemblages they host, with assemblage variation shaped by structural differences among habitats. The three habitat extremes also apply to the size structure and daily productivity of epifaunal assemblages, both important ecological properties with regards to the availability of this trophic group at a critical basal level in shallow reef food webs. Despite distinct assemblage-habitat associations and the variation in dominant habitats across the latitudinal range studied ‚- from cool-temperate macroalgae-dominated reefs to tropical coral reefs ‚- daily community productivity of epifauna was largely invariant among sampling locations. On subtropical to tropical reefs, dramatically different epifaunal assemblages were evident on live versus dead coral habitat, with dead coral supporting density, biomass, and daily productivity of epifauna 1 ‚- 2 orders of magnitude higher than live coral. These distinctions between broadly classified coral habitats were consistent among four heterogenous subtropical and tropical reef locations. Epifaunal communities apparently represent an important avenue for ecological change associated with coral mortality through mass bleaching events. Overall, my research strongly implies that habitat is the dominant driver of variation in reef-associated epifaunal assemblages. Broad-scale ocean warming and local anthropogenic stressors will likely influence changes to epifaunal assemblages on shallow reefs almost exclusively via transformation of habitats. The consistent trends across large biogeographic scales also suggest that accurate prediction of the basal food web resource provided by epifaunal invertebrates is possible when information on habitat distribution is available.


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Copyright 2021 the author Chapter 2 appears to be the equivalent of a post-print version of an article published as: Fraser, K. M., Stuart-Smith, R. D., Ling, S. D., Heather, F. J., Edgar, G. J., 2020. Taxonomic composition of mobile epifaunal invertebrate assemblages on diverse benthic microhabitats from temperate to tropical reefs, Marine ecology progress series, 640, 31-43. Copyright Copyright 2020 Inter-Research. Chapter 3 appears to be the equivalent of the peer reviewed version of the following article: Fraser, K. M., Stuart-Smith, R. D., Ling, S. D., Edgar, G. J., 2020. Small invertebrate consumers produce consistent size spectra across reef habitats and climatic zones, Oikos, 130(1), 156-170, which has been published in final form at This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley's version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited Chapter 4 appears to be the equivalent of a pre-print version of an article published as: Fraser, K. M., Stuart-Smith, R. D., Ling, S. D., Edgar, G. J., 2021. High biomass and productivity of epifaunal invertebrates living amongst dead coral, Marine biology, 168, 102 Chapter 5 appears to be the equivalent of a post-print version of an article published as: Fraser, K. M., Lefcheck, J. S., Ling, S. D., Mellin, C., Stuart-Smith, R. D., Edgar, G. J., 2020. Production of mobile invertebrate communities on shallow reefs from temperate to tropical seas, Proceedings of the Royal Society B: Biological sciences, 287(1941), 20201798

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