Understanding crown-of-thorns starfish outbreaks

The crown-of-thorns starfish (COTS) is a natural predator of corals in the Indo‐Pacific region, including the Great Barrier Reef (GBR). While they are native to the region, COTS are a leading cause of coral loss on the GBR. Since the 1960s, the Reef has experienced three recorded major outbreaks of COTS, with populations erupting approximately every 15 years. A fourth outbreak is now in progress.  As with the previous outbreaks, it started on reefs between Cairns and Lizard Island, and spread south, with large numbers now found in the Townsville region.  

During the spawning season, we conduct multiple experiments in which we raise COTS larvae until they can settle onto the reef surface. Most of these experiments test the importance of food (small algae) in the survival of the COTS larvae to investigate if increased nutrient runoff from landuse changes or natural nutrient sources may cause COTS outbreaks, as well as testing global change-related factors. 

Once we raise the young starfish for a few months, we will test which reef invertebrates are important predators of this species.

stage of COTS lifecycle under microscope
The crown-of-thorns starfish lifecycle

With help of SeaSim staff, we have developed a flow through larval culture system which allows raising larvae under more natural conditions. Larvae cultured in the SeaSim also assist in other COTS research, such as developing eDNA approaches to monitor COTS larvae and adults.

We will have several visitors from JCU this year who will measure COTS larval settlement on different substrates and develop a method to detect newly-recruited settlers on reefs using eDNA.

 

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