COTS Predation and Cyclones Make Corals More Susceptible to Disease

Crown-of-Thorns Starfish. Photo credits: Richard Catlin

Crown-of-Thorns Starfish. Photo credits: Richard Catlin

Coral reefs are some of the world’s most biodiverse ecosystems. They are host to over a quarter of all known fish species.

As I’m sure you are fully aware, the future of this ecosystem is looking pretty bleak. With the onset of global warming, the incidents of coral bleaching are predicted to increase. But for reefs such as the Great Barrier Reef (GBR) there are other additional threats to worry about.  Crown-of-thorns starfish (COTS) predation and cyclones cause a huge amount of damage to the GBR and have also been predicted to increase in future years. Currently, according to the Great Barrier Reef Marine Park Authority website, COTS outbreaks account for 42% of damage to the reef, whilst cyclones account for 48%.

Crown-of-thorns predation is a threat to reefs in the Indo-Pacific region due to their huge population outbreaks and consume vast amounts of coral. The causes of the outbreaks are still unclear, part of it is to do with their life-cycle and that females can release 60 million eggs in one spawning season and their lack of predators due to their unpalatability. Yet this still doesn’t explain the random outbreak events. One theory is that an increase in nutrients in an area will spark algal blooms, allowing more food for Crown-of-Thorns larvae, which then leads to increased adult recruitment.

A study recently published in the journal Coral Reefs, has revealed evidence that these threats come with an additional problem; increased susceptibility to coral diseases such as Brown Band Disease (BrB). BrB manifests on corals as a ciliate dominated lesion and leads to extensive mortality. Laboratory controlled experiments showed that BrB only infected those corals which had been previously predated on by a Crown-of-Thorns or had been physically damaged in a tropical storm. No healthy corals were affected.

This research shows that there is a lot we need to consider when trying to manage and prevent these threats. It is clear that further study is needed in getting to the root cause of the COTS outbreaks and also into disease prevention action.

 

References:

GBRMPA, 2011. Available from: http://www.gbrmpa.gov.au/about-the-reef/animals/crown-of-thorns-starfish. Date accessed (24/09/14)

Katz, S.M. et al, 2014. Crown-of-thorns starfish predation and physical injuries promote brown band disease on corals. Coral Reefs 33, 705–716. doi:10.1007/s00338-014-1153-2

Michael J. Kaiser, 2011. Marine Ecology: Processes, systems and impacts, Second. ed. Oxford University Press, Oxford.

 

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