[Coral-List] New publication on COTS outbreaks

Kayal Mohsen mohsen_kayal at yahoo.fr
Tue Oct 9 23:08:37 EDT 2012

Dear listers,

The crown-of-thorns starfish (COTS) is drawing much attention lately, as a recrudescence of outbreaks seems to be observed in several regions of the Indo-Pacific. To contribute to the debate, I would like to notify publication of our study on the dynamics of a recent COTS outbreak that affected the island of Moorea in French Polynesia (published as Open Access in PLoS ONE):


Mohsen Kayal, Julie Vercelloni, Thierry Lison de Loma, Pauline Bosserelle, Yannick Chancerelle, Sylvie Geoffroy, Céline Stievenart, François Michonneau,Lucie Penin, Serge Planes, Mehdi Adjeroud (2012) Predator Crown-of-Thorns Starfish (Acanthaster planci) Outbreak, Mass Mortality of Corals, and Cascading Effects on Reef Fish and Benthic Communities. PLoS ONE 7(10): e47363. doi:10.1371/journal.pone.0047363

Our observations at the island scale revealed a clear pattern of propagation of COTS densities, from a restricted area confined to the base of one reef (where COTS densities were first observed) to the entire insular reef system, based on a consecutive migration of starfishes toward adjacent and shallower reef areas (feeding front). This diffusive pattern of COTS was consistent with observations from surrounding islands, but also from reports from previous outbreaks in several regions. As a metaphor, I would compare such outbreaks to a forest fire that would start locally, and progressively spread to nearby areas to consume the resources. For management issues, this similarity with forest fires implies that COTS outbreaks in such insular reef systems are easier to control if acting at the earliest stages, when starfishes are confined to small reef areas.

As it is often the case, COTS aggregations were detected on reefs when starfishes were already adult and attacking corals. Thus, we have no clues about if all starfishes recruited in the same area, of if they recruited on different reefs and subsequently gathered in a same area. We also lack understanding of why specific reef areas constitute sources for such outbreaks. 

The densities of COTS observed in Moorea were particularly high (up to 30.3 +6.1 SE ind/200m2 transect, equivalent to > 150 000 ind/km2), generating a net and rapid collapse of coral populations, and cascading effects on algae and fish communities (as quantitatively reported in the paper).



Dr Mohsen Kayal (PhD)
IRD, U227 Coreus2
BP A5, 98848 Noumea
New Caledonia
mohsen.kayal at gmail.com

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