June 2004
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CROWN-OF-THORNS STARFISH
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| Crown-of-thorns
starfish. Photo by Katharina Fabricius, AIMS. |
The collaborative effort of CRC Reef scientists Dr Glenn De’ath, Dr Katharina Fabricius and Dr Ken Okaji from the Australian Institute of Marine Science (AIMS), and Mr Jon Brodie from James Cook University (JCU), may end 40 years of intense scientific and community debate as to whether crown-of-thorns outbreaks are a natural phenomenon, or whether they are exacerbated by human activities.
Water quality expert Mr Jon Brodie said the study shows an increase in nutrient run-off has led to higher levels of phytoplankton, which is food for the starfish larvae.
“The levels of nutrients such as nitrate, ammonia and phosphate that run into rivers and out onto the Great Barrier Reef have spiralled since 1850, particularly near developed areas,” Mr Brodie said. “Cropping, grazing and urban development are responsible for the rise in nutrient levels.”
Statistical modeller Dr Glenn De’ath said laboratory experiments reveal that twice as much phytoplankton results in a ten-fold increase in survival of the starfish larvae. This could stimulate a population explosion causing severe outbreaks of adult starfish.
A computer model developed by Dr De’ath predicts that such a doubling of phytoplankton will create more frequent outbreaks, from one every 50-100 years to one every 15 years; frequencies consistent with those observed in the northern and central Great Barrier Reef.
The scientists believe the research demonstrates that improved water quality will create greater coral cover and a healthier reef by reducing the frequency of crown-of-thorns starfish outbreaks.
For more information contact Mr Jon Brodie, jon.brodie@jcu.edu.au
or Dr Glenn De’ath, g.death@aims.gov.au
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CRC Reef Research Centre Ltd
PO Box 772 Townsville
Queensland 4810 Australia
Telephone: 61 47298400
Facsimile: 6147298499
Email: Info@crcreef.com
Website: www.reef.crc.org.au
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