Crown-of-thorns starfish outbreaks have wreaked havoc on the Great Barrier Reef’s several reefs since 1962. In the World Heritage Area, a fourth outbreak is now ongoing.
Crown-of-thorns starfish (also known as COTS) are coral-eating marine invertebrates. They’re found on reefs all around the Indo-Pacific, and when the conditions are right, they may spread like a plague, decimating hard coral communities.
After coral bleaching, crown-of-thorns starfish are a major driver of coral loss on the Great Barrier Reef, according to our research.
On the Reef, AIMS manages a large crown-of-thorns starfish monitoring program. Over a 15-year period, this long-term study found that epidemics start in the north and travel south, with ocean currents moving larvae between reefs.
The surveys also reveal that good reefs rebound after outbreaks, but it takes 10 to 20 years. However, reefs that are subjected to additional stresses, such as coral bleaching, cyclones, or poor water quality, take longer to recover, and the coral may not fully recover before the next round of breakouts.
Where did the crown-of-thorns starfish come from?
We have two crews of 10 to 12 divers out in the ocean all year, regardless of the weather, culling and removing crown-of-thorns starfish. They rotate 10 days on and four days off.
‘It feels like we’re at war at times, but we’re obviously winning; we’re witnessing coral regrowth and can see the difference.’
The crown-of-thorns starfish, which is native to the Indo-Pacific region, performs an important biological role in maintaining the reef’s diversity and delicate balance by feeding on the fastest-growing corals, allowing slower-growing coral species to form colonies. However, when the population of deadly starfish grows to epidemic proportions, it poses a serious threat to coral.
The first crown-of-thorns outbreak on the reef was documented in 1962, with further major outbreaks from 1978 to 1991, 1993 to 2005, and the current outbreak, which began in 2010, following.
Coral cover on measured reefs has decreased by roughly 50% over the last 30 years, according to study from the Australian Institute of Marine Science. Nearly half of the decline was caused by crown-of-thorns starfish. According to the study, if crown-of-thorns starfish predation had not happened during the preceding three decades, average coral cover would have increased.
Water quality drops substantially when huge amounts of nutrients from land are released into the reef, and if this happens during the starfish’s summer spawning season, conditions are ideal for the starfish to develop, grow, and survive at a much faster rate.
The Australian Government, the Great Barrier Reef Marine Park Authority, the Reef and Rainforest Research Centre, and the Association of Marine Park Tourism Operators joined forces under the Australian Government’s crown-of-thorns starfish control program to protect corals on high-value reefs from this and future outbreaks. Projects like the Game Changer case study are also addressing declining water quality.
Since its launch in 2011, the program has combed over 80 reefs and removed over 300,000 deadly coral predators.
More than $7 million has been allocated by the Australian government for two 20-meter control vessels, research and development, and the training and operation of diving teams.
‘It’s dangerous job, so proper training and control of diver tiredness is critical,’ Steve said.
‘On the control vessels, we have a policy that if a diver has been spiked more than twice, they are no longer allowed to dive.’
The invention of a single injection cull procedure by James Cook University was a big breakthrough for the program. To cull the creature, a little single injection causes an allergic reaction in the starfish, causing it to break apart and die within 24 hours.
To get the same result, divers had to take the starfish from its original place and inject it more than 20 times.
‘The starfish are unable to cope with the toxin and have broken up in the water, making the dive much faster and safer for the divers and the reef,’ Steve explained.
The new procedure is thought to have resulted in a two-and-a-half-fold boost in injection efficiency. The results have been spectacular, with 27 000 starfish removed in eight days at Arlington Reef, 9000 at Batt Reef, and 14 000 at Spitfire Reef near Cooktown.
The crown-of-thorns starfish control program’s astonishing achievement is a vital component of the Australian government’s overall strategic strategy to protecting the World Heritage-listed Great Barrier Reef.
Are crown thorns starfish introduced Australia?
The Crown of Thorns Starfish, also known by its abbreviation COTS, is responsible for around 42 percent of coral destruction on Australia’s Great Barrier Reef.
In reality, coral reefs all across the world are being harmed by outbreaks of this marine pest. The Atlantic Ocean is the only place where epidemic sightings have been reported so far.
This coral-eating starfish poses a threat to Australia’s tourism and fishing businesses, as well as the World Heritage-listed Great Barrier Reef itself, on a local level in North Queensland.
We wanted to learn more about the Crown of Thorns Starfish because it is one of the greatest dangers to the Great Barrier Reef’s survival.
We were fortunate to meet with two local specialists, Col McKenzie from the Association of Marine Park Tourism Operators (AMPTO) and Sheriden Morris from the Reef and Rainforest Research Centre, who are both at the forefront of COTS research and management (RRRC).
- COTS have been there for millions of years, according to fossil evidence, but outbreaks have only been seen in the last 50 years or so.
- COTS are a normal element of the ecology, and they only become overabundant when the reef is out of balance and sick.
- COTS can play a beneficial role in a healthy reef by devouring some of the faster-growing corals and allowing the slower-growing corals to catch up and rebuild.
- COTS was initially discovered in the Ryukyu Islands off the coast of Japan in the 1950s.
- The first COTS outbreak in Australia was discovered on Green Island in 1962. In Australia, there have been three to four outbreaks so far.
- Triton’s trumpet, white spotted puffer fish, lined worm, harlequin shrimp, and two species of triggerfish are among the few predators found in the Crown of Thorns (yellowmargin triggerfish and titan triggerfish). Red emperors, spangled emperors, and parrotfish have all been reported to devour young COTS before they develop spikes.
- Between October and March, when water temperatures are at their greatest, COTS spawn on the Great Barrier Reef. COTS females release eggs into the water, which are fertilized by sperm released by neighboring males. COTS with large females can lay up to 65 million eggs every season.
- COTS begin their lives as planktonic larvae that float on top of the sea for weeks before settling at the ocean’s bottom. They are most vulnerable to predators while they are young, before their spiky spines have fully developed. They acquire spines around the age of a year and begin to feed on coral.
- COTS can reach a diameter of one metre and have up to 21 arms as adults. They recover an arm within six months if they lose one due to stress or injury.
- COTS spines are long and pointy, with a thin epidermis that contains the venom ‘plancitoxin.’ Both marine life and humans are poisoned by them.
- COTS consume by passing their stomach through their mouth and spreading it all over the coral’s surface with their tube feet. The meal is then digested externally.
- Scleractinian is nearly solely consumed by adult COTS. They can go for up to nine months without eating.
COTS outbreaks are a threat to the Great Barrier Reef’s future because they are occurring more frequently and there is insufficient time for coral to rebuild between outbreaks.
Although a 15-year interval between outbreaks is reasonable, additional environmental factors such as cyclones and coral bleaching are putting the Reef at risk.
Several variables, according to research, are contributing to the rising number of COTS outbreaks. Excess nutrients in the water as a result of fertilizers and sewage runoff from the land, as well as overfishing, which reduces the number of natural predators, are examples.
In 2012, the AMPTO launched a COTS Targeted Control Program to protect dive sites. Throughout the year, a crew of 22 divers works to destroy COTS in these locations by injecting them with bile salts.
While this technique may work for dive locations that are essential to tourism operators, it is clearly not possible for bigger areas (and, let’s not forget, the Great Barrier Reef runs for over 2300 kilometers).
The Reef and Rainforest Research Centre (RRRC) is pursuing a more holistic approach and investigating strategies to address Crown of Thorns Starfish outbreaks in the same manner as agricultural pests are dealt with.
How did the crown-of-thorns starfish get to the Great Barrier Reef?
Scientists usually link outbreaks of the crown-of-thorns starfish to nitrogen spikes in the ocean caused by coastal and agricultural run-off.
As a result, outbreaks tend to occur further north and closer to the coast, but the Swain Reefs are located far offshore and on the southern end of the reef, therefore the origin of the outbreak remains unknown.
“It could be caused by nutrient upwelling from deep ocean waters,” he said, “but that hasn’t been demonstrated conclusively.”
He said that the Swains Reefs had been affected by a crown-of-thorns infestation in the 1990s but had recovered.
Because of its remote location at the southern end of the reef system, he felt optimistic that the area could be saved.
“The good news is that those reefs in the far southern area of the marine park have survived the substantial stresses that have resulted from mass bleaching occurrences in the last two years,” Mr Nucifora said.
“The fastest growing coral species that are largely present in that area are our staghorn and plate corals,” he said.
Is the crown-of-thorns starfish an introduced species?
She isn’t an invasive species. Natural predators of coral on the Great Barrier Reef and coral reefs from the Red Sea to the west coast of the Americas are crown-of-thorns starfish.
What was the crown-of-thorns made of?
They were moved to Notre Dame in 1806, where they were worshipped by the entire city of Paris.
Every Good Friday at a special liturgy at Notre Dame, the crown of thorns, now preserved in a gilded and crystalline reliquary, is brought out for the devout.
A twisted wreath of rushes from Juncus balticus, a perpetually flowering rush native to northern Britain, the Baltic, and Scandinavia, forms the crown.
The Ziziphus spina-christi plant provides the thorns seen in numerous reliquaries, notably the rooster that guarded Notre Dame’s pinnacle until the fire broke out.
The oldest known Ziziphus is said to be 2000 years old and grows near Ein Hatzeva, Israel, south of Jerusalem.
What happened to the crown-of-thorns?
The thornless remnants are housed in the treasury of Notre-Dame Cathedral in Paris, where they survived a horrific fire that devastated the roof and spire of the church in April 2019.
What is the purpose of crown-of-thorns starfish?
The crown-of-thorns starfish is so named because its body and limbs are covered in spines. In life, these spines are somewhat flexible and are used for mobility as well as defense against predators.
What kills crown-of-thorns starfish?
Scientists have discovered that a swarm of coral-eating starfish that has generated panic due to their seemingly relentless attack on the Great Barrier Reef may be killed off with a simple dosage of household vinegar.
Crown-of-thorns starfish, along with cyclones, are thought to be one of the two main causes of the Great Barrier Reef’s rapid loss of coral cover during the last 30 years.
When the conditions are favorable, such as when phytoplankton, their food source, becomes more abundant due to floods washing fertilizers and other contaminants from land into the water, the starfish can become plague-like.
A recent starfish outbreak has chewed through significant portions of the reef, pushing scientists to come up with novel measures to stop the disease.
Researchers at James Cook University have discovered that a single injection of vinegar kills the coral-eating starfish completely.
All starfish given 20ml of vinegar died within 48 hours, according to university experiments. The study will now move on to sea trials.
Currently, to kill a starfish, divers must inject 10 to 12ml of ox bile into it. Unlike vinegar, which is readily accessible in the grocery, ox bile is expensive, requires many licenses, and must be combined to the proper concentration.
However, the breakthrough isn’t a vinegary silver bullet; there’s still no other way to deliver the vinegar except by injecting starfish one by one.
The lead author of the JCU report, Lisa Bostrom-Einarsson, said more research was needed to guarantee the vinegar did not harm other sea creatures.
“There’s no reason to believe it won’t work or be unsafe,” she said, “but we have to be sure.”
“It is estimated that there are between four and twelve million starfish on the Great Barrier Reef alone, with each female producing approximately 65 million eggs in a single reproductive season.”
“With two full-time boat crews, they managed to kill roughly 350,000 people last year.” While culling them all that way would be impossible, we know that continuous efforts can conserve certain reefs.”
Crown-of-thorns eradication efforts are funded by the federal government, with 27 maritime tourism companies and two community groups certified to eradicate them.
However, according to the most recent report card on the Great Barrier Reef’s health, targets for reducing chemical runoff are not being met, making future outbreaks more likely.
Where did the crown-of-thorns starfish invade?
During the 1960s and 1980s, large colonies of crown-of-thorns starfish (also known as plagues) were discovered at 21 different locations on coral reefs. From the Red Sea through the tropical Indo-Pacific region to French Polynesia, these destinations were visited. At least two confirmed recurrent outbreaks occurred in ten of these locales.
In some studies, starfish concentrations of 140 to 1,000/ha have been called outbreak populations, while densities of fewer than 100/ha have been regarded low; nonetheless, at densities below 100/ha, A. planci eating may outpace coral growth, resulting in a net loss of coral.
Large abundances of Acanthaster spp. can be classified as follows based on surveys of various reef areas throughout the starfish’s distribution:
- Primary outbreaks, which are defined as sudden population increases of at least two orders of magnitude that are not explained by the presence of a preceding outbreak.
- Secondary outbreaks could be linked to past outbreaks due of the reproduction of a previous starfish cohort. These could show up as recruits to reefs downstream from an outbreak population.
- Chronic circumstances happen when a moderate to high density population of starfish exists at a reef area where the coral is scarce due to the starfish’s constant feeding.
Because of its length, number of individual reefs, and species richness, the Great Barrier Reef (GBR) is the world’s most impressive coral reef system. When significant populations of Acanthaster, which were causing heavy coral death, were initially discovered around Green Island, off Cairns, in 196065, there was a lot of concern. A number of reefs to the south of Green Island, in the central GBR zone, were later discovered to have high-density populations. Some popular publications, such as Requiem for the Reef and Crown of Thorns: The Death of the Barrier Reef?, stated that the entire reef was in risk of dying, influencing and reflecting public concern about the GBR’s status and future.
A number of research have used the GBR to model population breakouts in order to better understand the phenomenon.
During a period of tremendous concern about the nature of the starfish outbreaks on the GBR, the Australian and Queensland governments supported research and established advisory groups. They were accused of failing to comprehend the problem’s extraordinary severity and scope. Many scientists have been chastised for being unable to provide conclusive but unsupported answers. Others were more forthright in their responses. Scientists were chastised for their hesitancy and disagreements about the nature and origins of the GBR outbreaks, dubbed the “starfish wars” by some.