Dr Sven Uthicke1, Mrs Frances Patel, Dr Maria Gomez Cabrera, Mr Jason Doyle
1Australian Institute of Marine Science, Townsville, Australia
Innovative early warning tools are required for timely intervention of current crown-of-thorns seastar (CoTS) outbreak spread and future outbreaks. Based on CoTS specific primers and highly sensitive digital droplet PCR (ddPCR) we have developed eDNA methods that allow us to quantify CoTS larvae in plankton samples and to detect post-settlement CoTS on reefs with sensitivity much higher than traditional diver-based surveys.
CoTS larval eDNA work has been supported by citizen scientists such as tourism operators and CoTS Control Vessels, which allowed us to accumulate > 7000 plankton samples since 2014. This dataset can now be employed to i) elucidate spawning times and patterns, ii) investigate larvae distribution and connectivity, iii) examine relationship between CoTS larvae and water quality. In a monitoring context, detection of CoTS larvae constitutes the earliest possible indicator for population build-up.
CoTS post-settled eDNA work aims at identifying trace amounts of CoTS eDNA in a small volume of seawater. Using linear models of average copy numbers and occupancy modelling we demonstrated that CoTS densities below those classified as ‘outbreak levels’ can be detected and deviations from baseline (=population build-up) can be employed for early warning.
We now work on integrating larval and post-settlement eDNA monitoring into a large-scale CoTS monitoring program for early warning detection and to assist efficient CoTS control.
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