Taylor Whitman - AIMS@JCU

Taylor Whitman

taylor.whitman@my.jcu.edu.au

PhD
College of Science and Engineering

Taylor Whitman

taylor.whitman@my.jcu.edu.au

PhD
College of Science and Engineering
Identifying the biological and environmental drivers that underpin successful coral recruitment to inform restoration of modern reefs

Taylor is originally from California, United States, where she grew up fascinated by the temperate oceans and Redwood forests. After primary school, she traveled to Hawai'i to complete a Bachelor of Science degree in Marine Biology at the University of Hawai'i at Manoa. The major focus of her degree pertained to invertebrate biology and ecology, with a major focus on coral ecology and physiology. Her passion for tropical marine research led her to James Cook University (Townsville, Australia) to complete a Masters of Science in Marine Biology and Ecology degree. During this time, she completed a minor research project in collaboration with the Australian Institute of Marine biology, investigating the role of biochemicals cues from crustose coralline algae (CCA) to induce settlement of diverse coral taxa. She published that work as first author in the journal Scientific Reports and her results reinforced our understanding of the inductive role of CCA for acroporid corals, while demonstrating a lack of induction in several other genera, suggesting that other environmental cues may be responsible for the induction of non-acroporid coral larvae on reefs. These experiences have led her to where she is today, a PhD candidate ready to explore the biological and environmental drivers of coral recruitment.

Identifying the biological and environmental drivers that underpin successful coral recruitment to inform restoration of modern reefs

2021 to 2024

Project Description

Recruitment of coral larvae plays a critical role in the resilience and recovery of coral populations as the intensity and frequency of disturbances, such as temperature-induced coral bleaching, are increased due to anthropogenic climate change. Past research has strived to understand coral population dynamics by identifying the biological and environmental processes that underpin coral recruitment dynamics. However, there are many context-specific environmental drivers that influence the arrival and survival of coral propagules on reefs and these mechanisms are not adequately understood. This knowledge is needed prior to the implementation of direct restoration initiatives, such as larval enhancement and coral seeding experiments. Thus, assessing these drivers for reefs, such as those within the Keppel and Palm Island groups (Great Barrier Reef, Australia), that have experienced historically low levels of settlement and recruitment, is a key research priority. This project aims to test coral restoration and re-seeding methods across inshore and offshore reef gradients to identify drivers that cause differences in settlement and post-settlement survival dynamics. A mixed methodology approach will be used to pinpoint drivers of mortality and to test methods to maximise growth and survival of coral recruits to optimise cost-effective, field-based restoration that relies on the mass culture and settlement of diverse coral larvae.
This project will be undertaken as a collaboration between the Australian Institute of Marine Science, JCU, and the Reef Restoration and Adaptation Program (RRAP).

Project Importance

Recent restoration research has suggested that the addition of corals into the population via sexual reproduction provides a scalable and cost-effective potential method to restore reefs after disturbances. Coral recovery relies on the successful settlement of larvae and subsequent survival throughout the recruitment phase to reach reproductive maturity, where colonies can then contribute to future generations. Direct restoration initiatives aimed to facilitate rapid settlement, growth, and survival of sexually produced corals, such as larval enhancement and coral-seeding, have met with mixed success, with some efforts achieving greater than 50% recruit survival and the re-establishment of breeding colonies after 3 years. However, most efforts are not successful, and existing research has failed to identify the biological and environmental drivers that dictate recruit success or failure. Therefore, characterising the site-specific nature of processes and mechanisms influencing the survival of transplanted coral recruits on to reefs is necessary to implement cost-effective, field-based restoration.
Inshore reef environments, such as the Keppel Island group, have historically experienced acute disturbance events from freshwater flooding, high nutrient loads, and temperature driven mass bleaching. Yet, corals within this region have shown inherent resistance to these events, displaying higher calcification and growths rates with the ability to rapidly regenerate from remnant coral tissues after bleaching mortality and subsequent agal overgrowth. However, reef recovery through the addition of coral larvae has been limited by naturally low levels of settlement and recruitment. Although Keppel Island coral populations show some resilience to disturbances, recent studies suggest that even the most resilient reefs are not able to withstand repeated disturbance events exacerbated by anthropogenic climate change without the addition of new recruits into the population. Therefore, this project will aim to understand and identify the limitations to recruitment in the Keppel Islands and other inshore and offshore reef assemblages, to 'pin-point' the drivers of recruit mortality, and to develop re-seeding techniques to overcome this post-settlement mortality bottleneck.

Project Methods

The study will use a combined field and laboratory approach to identify environmental drivers of recruit mortality for diverse coral species to optimise restoration techniques; a key research priority with the Reef Restoration and Adaptation Program. In the first instance, controlled laboratory experiments will be used to improve coral propagation with sexually reproduced coral larvae. Laboratory components will aim to: (1) identify optimal larval density and substrate numbers to maximise settlement and recruit survival, (2) optimise recruit growth in feeding experiments, (3) compare recruit growth and survival on condition substrates of varying age and (4) explore coral fragmentation methods with diverse species to maximise growth and survival. Laboratory techniques will involve: coral culturing, larval rearing, mass-settlement, substrate conditioning, and controlled experiments with settlement substrates.
Results from laboratory experiments will then be used optimise field-based coral restoration across inshore and offshore reef environments along the Central and Southern GBR. Field components will aim to: (1) re-establish coral settlement and subsequent dominance in bio-eroded reef zones through coral reseeding and micro-fragmentation, (2) track coral success and growth on different deployment devices (e.g. herbivore exclusion and anti-fouling devices), (3) compare coral survival and growth among device-level orientations (top, side, bottom), and (4) determine biological and environmental drivers of success and mortality within and across reef environments. Field techniques will include: SCUBA-based coral identification and collections, deployment and collection of in situ environmental data loggers, device deployment and census, benthic and fish surveys using imagery and video transects.

Project Results

This project hopes to find discrete biological and environmental variables linked to recruitment success across multiple coral species and reef habitats. This information will then be used to optimize coral re-seeding devices to be used in large-scale direct restoration initiatives. Since the project is in the beginning stages, device trialing and recruit-grow out have not been started yet. However, 250, 000 Acropora digitifera larvae have been reared from the March/Autumn coral spawning event and they will be mass-settled on herbivore exclusion and non-exclusion devices for an August deployment to Davies reef, Central Offshore, GBR. This marks the first successful attempt at culturing A. digitifera larvae at AIMS and the project will greatly benefit from the addition of an Autumn spawning coral to compare with the mass-spawning events in Summer (October/November).

Keywords

Algae,
Artificial reef,
Benthic,
Climate change,
Coral reefs,
Corals,
Ecology,
Field based,
Fish,
Manipulative experiments,
Modelling,
Natural disturbance,
Ocean warming,
Quantitative marine science

Supervised By:

Carly Randall (AIMS)

Mia Hoogenboom (JCU)

Andrew Negri (AIMS)