Distribution, abundance and life cycle of free-living Symbiodinium

Field	Value	Language
dc.contributor.author	Fujise, Risa
dc.date.accessioned	2018-10-09T00:26:31Z
dc.date.available	2018-10-09T00:26:31Z
dc.date.issued	2018
dc.identifier.uri	http://hdl.handle.net/10453/128000
dc.description	University of Technology Sydney. Faculty of Science.	en_AU
dc.description.abstract	Symbiodinium are endosymbiotic microalgae of reef-building corals. Photosynthesis by these algae fuels the productivity of corals and ultimately the growth of entire reef systems. However, a critical phase of Symbiodinium’s life history is existence as “free-living” cells prior to acquisition by their host. Free-living populations are essential for establishing symbiosis for many corals that propagate larval generation without algal symbionts, but also for recombination of host-symbiont associations recovering from stress. Despite the importance of free-living populations, their underlying biodiversity and ecology remains a black box. For example, how they distribute spatially, temporally and regionally, and contribute to coral reef ecosystems as they currently face an era of “ecological crisis”, are largely unknown. To unlock the distribution, abundance and life cycle of free-living Symbiodinium, I applied novel dual NGS- (eDNA metabarcoding using next generation sequencing) and qPCR-based (using clade-specific primers) approaches to first explore the qualitative and quantitative distribution and abundance of free-living Symbiodinium for tropical (Heron Island) (Chapter 2) and temperate (Sydney Harbour) (Chapter 3) east coast Australian coral communities that are periodically connected by the Eastern Australian Current. To further evaluate how such diversity (which is only a snap shot of population dynamics over time) is sustained as a result of individual population turnover, I analysed the Symbiodinium cell cycle to establish a novel baseline for how population turnover is regulated by cell cycle dynamics across species and under alternate conditions (light and temperature) (Chapter 4). This thesis highlights the importance of habitat variety in sustaining diverse free-living Symbiodinium communities, functional plasticity and hence resistance to disturbance (Chapter 5). For example, I provide new insight of macroalgae habitats as key reservoirs of symbiont availability to hosts via local supply but also wider dispersal. In the latter case, I discuss that dispersal of Symbiodinium is critical to support paradigms of high-latitude temperate reefs acting as refugia for tropical corals under climate change, since temperate and tropical Symbiodinium communities are currently geographically separated. Cell cycle dynamics differed between genetically different types (species), and results in specific types proliferating faster under certain environmental conditions thereby supporting shifts in community structure. As such, cell cycle dynamics comprises a key functional trait that is still overlooked but warrants further targeted investigation, not only amongst free-living populations, but also in hospite to clarify how functional equilibrium under steady-state symbioses is maintained as reef environments continue to be subjected to stressors into the future.	en_AU
dc.format	Thesis (PhD)
dc.language.iso	en_AU	en_AU
dc.relation	https://opus.lib.uts.edu.au/bitstream/10453/128000/2/02whole.pdf
dc.rights	The author owns the copyright in this thesis including all reproduction and reuse rights for the work. The work may not be altered without the permission of the copyright owner. Attribution is essential when quoting or paraphrasing from this thesis.
dc.rights	info:eu-repo/semantics/openAccess
dc.rights	au.edu.uts.lib/ppc
dc.subject	Symbiodinium.	en_AU
dc.subject	Endosymbiotic microalgae.	en_AU
dc.subject	Reef building corals.	en_AU
dc.subject	Reef ecology.	en_AU
dc.subject	Macroalgae habitats.	en-AU
dc.title	Distribution, abundance and life cycle of free-living Symbiodinium	en_AU
dc.type	Thesis	en_AU
utslib.copyright.status	open_access

Abstract:

Symbiodinium are endosymbiotic microalgae of reef-building corals. Photosynthesis by these algae fuels the productivity of corals and ultimately the growth of entire reef systems. However, a critical phase of Symbiodinium’s life history is existence as “free-living” cells prior to acquisition by their host. Free-living populations are essential for establishing symbiosis for many corals that propagate larval generation without algal symbionts, but also for recombination of host-symbiont associations recovering from stress. Despite the importance of free-living populations, their underlying biodiversity and ecology remains a black box. For example, how they distribute spatially, temporally and regionally, and contribute to coral reef ecosystems as they currently face an era of “ecological crisis”, are largely unknown. To unlock the distribution, abundance and life cycle of free-living Symbiodinium, I applied novel dual NGS- (eDNA metabarcoding using next generation sequencing) and qPCR-based (using clade-specific primers) approaches to first explore the qualitative and quantitative distribution and abundance of free-living Symbiodinium for tropical (Heron Island) (Chapter 2) and temperate (Sydney Harbour) (Chapter 3) east coast Australian coral communities that are periodically connected by the Eastern Australian Current. To further evaluate how such diversity (which is only a snap shot of population dynamics over time) is sustained as a result of individual population turnover, I analysed the Symbiodinium cell cycle to establish a novel baseline for how population turnover is regulated by cell cycle dynamics across species and under alternate conditions (light and temperature) (Chapter 4). This thesis highlights the importance of habitat variety in sustaining diverse free-living Symbiodinium communities, functional plasticity and hence resistance to disturbance (Chapter 5). For example, I provide new insight of macroalgae habitats as key reservoirs of symbiont availability to hosts via local supply but also wider dispersal. In the latter case, I discuss that dispersal of Symbiodinium is critical to support paradigms of high-latitude temperate reefs acting as refugia for tropical corals under climate change, since temperate and tropical Symbiodinium communities are currently geographically separated. Cell cycle dynamics differed between genetically different types (species), and results in specific types proliferating faster under certain environmental conditions thereby supporting shifts in community structure. As such, cell cycle dynamics comprises a key functional trait that is still overlooked but warrants further targeted investigation, not only amongst free-living populations, but also in hospite to clarify how functional equilibrium under steady-state symbioses is maintained as reef environments continue to be subjected to stressors into the future.

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