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Crown-of-thorns starfish pressure on the Great Barrier Reef

Key finding

Evidence suggests increased nutrient loads contribute to more frequent outbreaks of crown-of-thorns starfish — a major predator of coral — resulting in coral cover decline.

Great Barrier Reef marine park area (information applies statewide, map locations are for reference only)

Crown-of-thorns starfish are a major predator of coral and one of the major causes of coral cover decline in the Great Barrier Reef.

An adult crown-of-thorns starfish can consume an area of coral about the size of a dinner plate (478cm2) each day.

Under natural conditions, it is thought that crown-of thorns starfish populations increase to outbreak concentrations in a 50 to 80 year cycle. An outbreak is considered when they are at densities greater than 30 starfish per hectare. Human impacts appear to increasing the frequency and severity of crown-of-thorns starfish outbreaks to the Reef.

Each outbreak has resulted in severe reductions in coral cover on a regional scale, particularly in the central area of the region.

Increased nutrient loads flowing into reef waters from catchments appear to contribute to crown-of-thorns starfish outbreaks due to increased food supply and therefore survival of their larvae. Importantly, the increased frequency of outbreaks, combined with other stresses on corals, means coral populations are increasingly unable to fully recover before the next outbreak occurs.

Growing evidence indicates ecosystem conditions may have resulted in more frequent outbreaks of crown-of-thorns starfish over the past 30 years across much of the region. These have seriously affected the ecosystem.

More information:

Indicator: Crown-of-thorns starfish

Crown-of-thorns starfish pressure on the Great Barrier Reef Marine Park Area as reported in the Great Barrier Reef Outlook Report 2014.

Condition dial — grade 1 (Very poor) on a 1–4 scale

See also: Estuarine and marine ecosystems assessment summary.

Last updated 23 June 2020