Peter Doll - AIMS@JCU

Peter Doll

peterchristopher.doll@my.jcu.edu.au

PhD
ARC Centre of Excellence Coral Reef Studies

Peter Doll

peterchristopher.doll@my.jcu.edu.au

PhD
ARC Centre of Excellence Coral Reef Studies
Habitat suitability and patterns of larval settlement for crown-of-thorns starfish (Acanthaster cf. solaris) in the western Pacific

Peter Doll grew up in the Bavarian Alps, Germany, but his love for the ocean and its inhabitants brought him to Townsville in 2014. He completed his Bachelor of Science majoring in Marine Biology at James Cook University in 2017 and then joined the Jones Lab in 2018 to undertake an honours project under the supervision of Professor Geoff Jones and Professor Phil Munday. Peter examined habitat specialisation and the potential consequences of habitat loss in coral reef gobies of the genus Eviota and gained first-class Honours through doing so. Peter then began his PhD in 2020 at the ARC Centre of Excellence for Coral Reef Studies and AIMS, under the supervision of Professor Morgan Pratchett, Professor Andrew Hoey, Dr Ciemon Caballes, Jason Doyle and Dr Sven Uthicke. Peter’s PhD research will investigate habitat suitability and patterns of larval settlement for crown-of-thorns starfish in the western Pacific.

Habitat suitability and patterns of larval settlement for crown-of-thorns starfish (Acanthaster cf. solaris) in the western Pacific

2020 to 2023

Project Description

This project will explore patterns of larval settlement (measured using proven settlement cages and innovative genetic analyses) to answer 3 fundamental questions:
1) How do rates of larval settlement vary among habitats (e.g., with depth and exposure)? This study will be conducted in areas with established outbreaks of crown-of-thorns starfish, whereby settlement cages will be deployed in a range of environmental settings and habitats to test for spatial variation in rates of larval settlement.
2) Are rates of larval settlement related to local adult densities? Understanding stock-recruitment relationships are fundamental to understanding the population dynamics of this species, as well as the effectiveness of population regulation based on targeting adult starfish. I therefore propose to measure rates of larval settlement across a range of locations, both in areas with high and low densities of adult crown-of-thorns starfish.
3) What are the predominant settlement cues (or inhibitors) and can this account for geographical variation in the incidence of population irruptions? A combination of field and laboratory experiments will be conducted to test whether larval settlement rates are moderated by the local biological assemblages (e.g., by comparing among settlement substrates conditioned in different habitats) and thereby understand important determinants of larval settlement.

Project Importance

Changes in key demographic rates of CoTS, in particular the rates of larval production and successful settlement, are fundamental to rapid increases in local abundance. Detecting high recruitment pulses as early as possible is key to improve the timing and effectiveness of control activities and limit the extirpation of many corals. Most importantly, these studies will improve our understanding of the patterns and drivers of CoTS recruitment pulses and the quantification of CoTS settlement will contribute to the development of an effective early warning system using eDNA detection of adults, larvae and the settlement of CoTS.

Project Methods

This project will be conducted in areas with established outbreaks of crown-of-thorns starfish and patterns of larval settlement will be measured using proven settlement cages (filled with bioballs and attached to the reef) and innovative genetic analyses. These settlement cages will be deployed using SCUBA prior to the expected spawning (~ early November) and collected after the settlement seasons (~ February).
To test for spatial variation in rates of larval settlement, settlement cages will be deployed in a range of environmental settings and habitats. On each study reef, six replicate traps will be deployed at different exposures and depths.
To test whether the rates of larval settlement are related to local adult densities, the rates of larval settlement will be measured across a range of locations, both in areas with high and low densities of adult starfish. Adult densities will be measured by divers searching and counting adult crown-of-thorns starfish in a belt of 2m on either side of 50m replicate transects. Distribution patterns of newly settled crown-of-thorns starfish will be determined by extracting DNA subsamples from material in the collected cages and amplifying A. cf. solaris DNA in polymerase chain reactions (PCR).
A combination of field and laboratory experiments will be conducted to determine potential settlement cues (or inhibitors) for crown-of-thorns starfish. Here, we test whether larval settlement rates are moderated by different local biological assemblages (e.g., by comparing among settlement substrates conditioned in different habitats).

Project Results

While these recent studies won't commence until March 2020, pilot studies using the same field and laboratory methodologies provided convincing proof of concept that CoTS larvae settled in the purpose-built settlement traps. A protocol to successfully extract DNA from large samples, as well as amplify CoTS DNA in polymerase chain reactions (PCR) was successful. The successful development of a protocol that allows the detection of settlement in CoTS will now provide a tool for monitoring programs and an 'early-warning system' for new and renewed outbreaks of CoTS.

Keywords

Coral reefs,
Crown of Thorn Starfish,
Echinoderms,
Ecology,
Genetics,
Management tools,
Molecular techniques