Crown-of-thorns starfish (COTS) are marine invertebrates that
feed on coral and occur naturally on reefs throughout the
Indo-Pacific region. When conditions are right for COTS to
multiply, they can reach plague proportions and devastate the
hard coral population on affected reefs.
In the past 40 years, three major COTS outbreaks have had a
major impact on many reefs of the Great Barrier Reef (GBR). COTS
outbreaks are responsible for a greater decline in coral cover
than any other threat to the GBR.
AIMS has implemented the most comprehensive COTS monitoring
program in the world across the GBR. This long-term program,
combined with genetic studies, has shown that COTS outbreaks
begin in the north and migrate southward on ocean currents over a
15 year period. These surveys also show that healthy reefs
generally fully recover between outbreaks, taking 10-20 years to
do so. Reefs affected by additional stresses, such as coral
bleaching, cyclones or poor water quality, may take a lot longer.
In the laboratory, AIMS' experimental research has shown that
COTS larval survival increases dramatically as phytoplankton,
their food source, becomes more abundant. Although land runoff
rich in fertilisers and other pollutants can cause peaks in
phytoplankton, scientists are still unsure whether there is a
link between human activity and COTS outbreaks, given that the
biggest increases in phytoplankton production follow natural
events such as cyclones and high rainfall.