Thesis
Optimising mass culturing of coral larvae from wild coral spawn: enhancing survival and production for scalable reef restoration
Southern Cross University
Doctor of Philosophy (PhD), Southern Cross University
2025
DOI:
https://doi.org/10.25918/thesis.527
Appears in Recent Southern Cross PhD Theses
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Abstract
Coral reef restoration methods utilising sexually produced coral larvae from mass coral spawning events offer promising solutions to mitigate global coral depletion. Although this approach is considered scalable and cost-efficient, it remains in development. Wild coral spawn collection and rearing larvae in situ are limited to specific times each year and subjected to environmental variability. Scaling up coral larval production and settlement rates is a critical challenge for restoring reefs at ecologically relevant scales.
The research for this thesis aimed to advance our knowledge of mass culturing coral larvae in situ from wild coral spawn by testing spawn collection methods (Chapter 2), investigating slick densities and stocking effects on larval survival and settlement success (Chapter 3), and optimising rearing pool conditions with shading (Chapter 4).
Chapter 2 investigated coral spawn collection using traditional small-scale and industrial larger-scale methods during a time series immediately following spawning. The results showed that both collection method and timing significantly affected embryo integrity and larval and settler size. This study demonstrated how large-scale spawn collections can be done without compromising larval quality by carefully considering the collection method as embryos develop.
Chapter 3 focused on optimising larval production efficiency by rearing wild coral spawn slicks under varying slick coverage and density. This study revealed that increased slick coverage and density showed negative density-dependent effects on survival, development, and settlement success, but higher stocking densities enhanced the total production of competent larvae. Additionally, the increased abundance of competent larvae positively influenced the abundance of settlers, and settlers the abundance of recruits. The outcomes demonstrated the importance of both larval quality and supply and suggested opportunities for optimising larval production in mass cultures.
Chapter 4 explored the effects of shading in situ rearing pools on coral larvae. Shaded pools reduced the ultraviolet radiation (UVR) and temperature extremes, increasing larval production. However, lower temperatures in shaded pools delayed competency and reduced settlement rates compared to unshaded pools. An ex situ experiment, which controlled temperature while varying UVR, revealed that UVR alone did not significantly affect survival and settlement rates. Overall, both field and laboratory experiments suggest shade covers improve initial survival by reducing survival variability. However, removing covers during later development may help balance temperature and development rates.
Overall, this research offers solutions for enhancing mass production of coral larvae on reefs, contributing to the development of best practices for collecting and mass culturing wild slicks in situ.
Details
- Title
- Optimising mass culturing of coral larvae from wild coral spawn: enhancing survival and production for scalable reef restoration
- Creators
- Christina Langley
- Contributors
- Peter L Harrison (Supervisor) - Southern Cross UniversityDexter Dela Cruz (Supervisor) - Southern Cross UniversityChristopher Doropoulos (Supervisor) - Southern Cross University
- Awarding Institution
- Southern Cross University; Doctor of Philosophy (PhD)
- Theses
- Doctor of Philosophy (PhD), Southern Cross University
- Publisher
- Southern Cross University
- Number of pages
- 173
- Identifiers
- 991013324928702368
- Copyright
- © Christina Langley 2025
- Academic Unit
- Faculty of Science and Engineering
- Resource Type
- Thesis