Peter grew up in the Bavarian Alps and attained a Bachelor of Science with Honours (Class I) from James Cook University (JCU) in 2018. As part of his honours research, he examined habitat specialisation and consequences of habitat loss for cryptobenthic coral reef fishes in Papua New Guinea with Prof. Geoffrey Jones and Prof. Philip Munday. Working in the Pratchett Lab at the ARC Centre of Excellence for Coral Reef Studies (ARC CoE) in 2019-20, he conducted research on a broad range of topics including the biology and ecology of the corallivorous crown-of-thorns starfish (CoTS). His current PhD research on CoTS larval settlement at the ARC CoE/JCU is supported by JCU Postgraduate Research and ARC CoE scholarships, and Peter is also very grateful to the Australian Institute of Marine Science and AIMS@JCU for their continuing support.

Processes and patterns in larval settlement of crown-of-thorns starfish (Acanthaster cf. solaris)

2020 to 2023

Project Description

Population irruptions of the pervasive crown-of-thorns starfish (CoTS) are a perennial threat to coral reefs and may be initiated by fluctuations in settlement success. This project aims to improve the ecological underpinning for the management of destructive CoTS populations by resolving important and persistent knowledge gaps surrounding CoTS settlement. Using experimental and novel field sampling approaches, this research examines settlement induction by various chemical cues, spatiotemporal patterns in the field and their ecological drivers. Overall, this project aims to consolidate our understanding of this critical early life-history stage, and improve our ability to predict, detect and manage population irruptions of this destructive starfish.

Project Importance

The next primary population irruption of CoTS on the GBR will likely start in the next few years, and it appears critical that efforts to improve the ecological underpinning for management and early detection of pre-outbreak populations start as soon as possible, in order to prevent or suppress new and renewed population irruptions. Despite the important role of early life-history processes to the irruptive dynamics of starfish populations, settlement patterns of CoTS and the implications thereof have remained largely unexplored due to sampling limitations. A more detailed understanding of the mechanisms driving settlement and metamorphosis induction in A. cf. solaris may also have far reaching ramifications for innovative population control techniques in the future (e.g., semiochemicals). The innovative work conducted as part of this project has the potential to ultimately mitigate the detrimental impacts of CoTS on coral reefs.

Project Methods

A range of experimental studies has and will be conducted at the AIMS National Sea Simulator to test the effects of various chemical, physical and biological cues on CoTS settlement and metamorphosis. This project further introduces an innovative method to measure CoTS settlement during reproductive summer seasons, using artificial settlement collectors and droplet digital polymerase chain reaction based on CoTS specific mitochondrial DNA primers. This protocol provides an opportunity to explore spatiotemporal settlement patterns and their ecological drivers, combined with field-based surveys of conspecific adults, larvae, substrata and other environmental factors.

Project Results

Some of the components of this project have been published, including a review of the processes and patterns of larval settlement across all five echinoderms classes (Doll et al. 2022, Oceanogr. Mar. Biol.). Work on the DNA-based detection and patterns of CoTS larval settlement on the GBR revealed temporal and spatial variation in CoTS settlement and added to our understanding of this critical life-history stage (Doll et al. 2021, Biol. Bull.). Fluctuations in CoTS settlement can now be detected using the described protocol, which demonstrates its utility in heralding new and renewed CoTS population irruptions. Moreover, a recent laboratory study demonstrated settlement cue selectivity by CoTS larvae, challenged a hypothesis for deep water recruitment and linked coralline algae assemblages to the spatial heterogeneity in CoTS recruitment and adult population sizes. Further experimental research and molecular work is in progress and will be published in the near future.
Doll PC, Messmer V, Uthicke S, Doyle JR, Caballes CF, Pratchett MS (2021) DNA-based detection and patterns of larval settlement of the corallivorous crown-of-thorns sea star (Acanthaster sp.). The Biological Bulletin, 241: 271-285 (https://doi.org/10.1086/717539).
Doll PC, Caballes CF, Hoey AS, Uthicke S, Ling SD, Pratchett MS (2022) Larval settlement in echinoderms: a review of processes and patterns. Oceanography and Marine Biology: An Annual Review, 60: 433-494 (https://doi.org/10.1201/9781003288602-9).
Doll PC, Uthicke S, Caballes CF, Diaz-Pulido G, Abdul Wahab MA, Lang BJ, Jeong SY, Pratchett MS (2023) Settlement cue selectivity by larvae of the destructive crown-of-thorns starfish. Biology Letters, 20220399 (https://doi.org/10.1098/rsbl.2022.0399)

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