- Purple sea urchins (Strongylocentortus purpuratus) are native to the United States’ Pacific Coast. Natural predators of the purple sea urchin, such as sea otters and sea stars, have declined in numbers (Pearse 2006). The resulting population explosion of purple sea urchins has ravaged kelp forests, which are important homes for many marine animals (Pearse 2006).
- Europe and North Africa are home to the European Green Crab (Carcinus maenas). The crab, which is found in the Americas, Australia, and South Africa, preys on a wide range of creatures but is especially damaging to bivalves (Colnar & Landis 2007).
Why are crown-of-thorns starfish a problem?
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.
What is an invasive species in the Great Barrier Reef?
Crown-of-Thorns Starfish This kind of starfish is an invasive species in the Great Barrier Reef that feeds on coral polyps and can cause a lot of harm. Originally, the starfish was not invasive, but in the twentieth century, the starfish’s predators (such as the Pacific Triton) were overhunted. The crown-of-thorns starfish posed a menace to coral reefs since there were no predators to keep the population under control.
Ocean temperatures are rising as a result of climate change, particularly surface water temperatures like those surrounding the Great Barrier Reef. Coral bleaching can be caused by even minor temperature changes. Because of the dramatic nature of climate change, rising ocean temperatures are considered one of the greatest risks to the Great Barrier Reef.
Why was the crown-of-thorns starfish introduced to Australia?
The tranquil beauty of the seas between Lizard Island and Cairns on the Great Barrier Reef belies the war beneath the surface between teams of committed divers and the deadly, coral-destroying crown-of-thorns starfish.
The Association of Marine Park Tourism Operators, a key partner in the Australian Government’s crown-of-thorns starfish control program, said, “This is one of the biggest dangers to the reef that we can do something about on the ground.”
How does the crown-of-thorns starfish damage the Great Barrier Reef?
Crown-of-thorns During an outbreak, when the number of predators explodes, starfish can strip a reef of coral. The compounds they utilize to attract other starfish are revealed by analyzing their DNA and proteins in waterborne plumes when they spawn.
What do crown-of-thorns starfish look like?
The crown-of-thorns starfish (Acanthaster planci) has a central disk from which its arms emerge, similar to other starfish. They have many soft arms (more than the usual five) that are covered in spines, which distinguishes them from other creatures. Their arms are also prehensile, allowing them to grasp objects. Crown-of-thorns starfish can grow up to 10-14 in (25-35 cm) in length and have more than 20 limbs when fully grown. They’re also available in a range of colors, including bluish-purple, red, gray, and green.
How cute are they?
The COTS (a coral predator) is more interesting and appealing than cute. Their brilliant colors, such as purple, gray, and green, as well as their spiky body, are fascinating to observe.
How do they communicate?
The method these organisms communicate is mostly unknown. A recent study, however, may give some illumination, as it was discovered that they communicate with one another through chemical release. COTS from different places, such as COTS from the Indo-Pacific region (which are a coral reef pest) and COTS from Japan, have been found to release the same compounds. When they are attacked by a predator, they appear to emit various proteins, but there is still a lot more to discover about these fascinating aquatic critters.
How big is a crown-of-thorns starfish?
The average adult crown-of-thorns starfish is 10-14 inches long (25-35 cm). The long and pointed spines on the sides of the starfish’s arms and upper (aboral) surface resemble thistles, and can have up to 23 arms. They resemble a crown, which gives the animal its name. The spines are solid, pointed, and may easily puncture through fragile surfaces, growing up to 0.13 ft (4 cm) long.
How did it get its name?
The venomous thorn-like spines that cover the upper surface of the crown-of-thorns starfish (coral reef eater) give it its name. These resemble the biblical crown of thorns in appearance.
Would they make a good pet?
They cannot be kept as pets because they dwell in the waters and contribute to the balance of their ecosystems. Crown-of-thorns starfish are predators that eat a variety of corals. They can only live in the deepest parts of the ocean, where they may feed on vast amounts of corals.
Kidadl Recommendation: Only purchase pets from a reliable provider. It is important that you conduct your own research as a potential pet owner before deciding on your pet of choice. Being a pet owner is extremely rewarding, but it also necessitates a significant amount of time, effort, and money. Check to see if the pet you’ve chosen is legal in your state and/or nation. You must never capture wild animals or harm their habitat. Please double-check that the pet you’re thinking about buying isn’t an endangered species, isn’t on the CITES list, and hasn’t been captured in the wild for the pet trade.
Did you know…
One of the most interesting crown-of-thorns starfish facts for kids is that they feed on their prey, coral reef, by ejecting their stomachs from their bodies and covering the corals!
Crown-of-thorns starfish are nocturnal and can eat 53.8-140 square feet (5-13 square meters) of coral in a single year. COTS are the primary cause of reef damage in Australia’s Great Barrier Reef.
The poison of the crown-of-thorns starfish contains saponin, a chemical component that is deadly to both humans and fish. The sting of a crown-of-thorns starfish can produce numbness, tingling, nausea, and agony across the body.
On the Great Barrier Reef, AIMS has a large COTS checking operation. This long-term study found that epidemics start in the north and move south over 15 years, with the ocean transporting larvae between reefs.
Why is the crown-of-thorns starfish a problem?
Coral-eating crown-of-thorns starfish can be an issue. Under extreme circumstances, this sea star can have outbreaks that cause huge coral reef devastation, threatening the vital coral cover. Coral reefs are crucial for many undersea animals, and they also help to reduce the intensity of the waves that pound our coasts.
Can a crown-of-thorns starfish kill a human?
Although the venom of crown-of-thorns starfish (coral reef eater fish) cannot kill humans, their spines do contain neurotoxic and starfish poison, which is harmful to both humans and marine life.
We’ve painstakingly crafted a variety of interesting family-friendly animal facts for you to explore at Kidadl! Learn more about the ground beetle and the American dagger moth, two more arthropods.
You can even color one of our crown-of-thorns starfish coloring sheets at home to keep yourself occupied.
Are starfish invasive?
The Great Barrier Reef, one of the world’s seven natural wonders, is filled with tropical fish and coral species. However, the reef is currently being attacked by outbreaks of crown-of-thorns starfish, which feed on the coral that lives there. Is it possible for reefs to recover from this devastating invading species?
The Great Barrier Reef, which stretches for 347,058 square kilometers (134,000 square miles) along Queensland’s coast, is home to over 1,500 tropical fish and 400 coral species.
3This natural wonder is so rich in life that it was designated as a United Nations Educational, Scientific, and Cultural Organization (UNESCO) World Heritage site in 1981.
3,5Unfortunately, the reef is on the list of World Heritage in Danger because of several environmental problems that have badly harmed it.
3,5Between 1985 and 2012, about half of the reef’s coral disappeared, with crown-of-thorns starfish infestations accounting for roughly 42% of the decrease (COTS).
3,4,6,8
The crown-of-thorns starfish, or Acanthaster planci, is a huge echinoderm that feeds on coral and is covered in thorn-like spikes.
2,9Although the starfish is native to the Indo-Pacific region, it has been labeled an invasive species due to its dense populations and the damage it is wreaking on the Great Barrier Reef.
3,10This predator loves fast-growing coral but will eat boulder coral, which is a massive coral formation that takes hundreds of years to build.
2
As the starfish coils around their meal and ejects their stomachs into the coral, the coral is digested outside of their bodies.4
The environmental causes that have contributed to the breakouts of these starfish have sparked debate among scientists.
The role of anthropogenic effect has been underlined in both of the primary hypotheses.
The predator elimination theory and the terrestrial runoff hypothesis are 1,3,5 respectively.
10
According to the predator removal hypothesis, the population of crown-of-thorns starfish has increased due to predator overfishing.
1,10The proposed remedy is to impose a commercial fishing restriction “No-take” zones
1,4It’s thought that this solution will have a trickle-down effect.
4
These bans protect huge fish, which prey on smaller fish, which prey on the invertebrates that consume starfish larvae.
4 If large fish populations decline owing to commercial fishing, small fish populations will increase, and the number of larvae consuming invertebrates would plummet, resulting in an increase in crown-of-thorns starfish. 4 Researchers discovered that there were up to seven times fewer outbreaks of crown-of-thorns starfish in the past than in the present “no-take” zones than in areas where commercial fishing is not prohibited. 4
Increases in crown-of-thorns populations, according to the terrestrial runoff theory, can be ascribed to an increased amount of terrestrial nutrients in the water after large rainfall or runoff events.
3,5,10Excess nutrients promote denser phytoplankton populations, which promote larval survival and the production of more adult crown-of-thorns starfish.
Both hypotheses provide insight into the probable causes of outbreaks, but verifying them has been impeded by the inability to analyze the spatiotemporal distribution of crown-of-thorns larvae since they resemble other planktotrophic echinoderm larvae.
8
A group of researchers, on the other hand, was able to create a genetic identifier and test it on 48 plankton samples obtained during the 2014 spawning season in the northern Great Barrier Reef.
Polymerase chain reaction (PCR) amplification of a single larva was used to confirm the genetic marker.
8
The majority of the samples tested positive for crown-of-thorns larvae, which were found up to 100 kilometers (62 miles) south of current outbreaks.
8
These findings point to the potential for outbreaks to spread quickly, and the establishment of a genetic marker will aid in the detection of such outbreaks.
8
Reefs, fortunately, may reclaim their coral cover.
The procedure, however, is slow and takes anywhere from 10 to 20 years.
3Only if the crown-of-thorns populations are kept under control will this be possible.
Previously, divers were completely responsible for this task.
2Divers were supposed to physically remove these predators from their natural habitats or inject them with a poison.
2Divers will now have the help of the COTSbot, an automated vehicle that is programmed to patrol the Great Barrier Reef and kill any crown-of-thorns starfish it identifies through fatal injection (Figure 5).
6The COTSbot scans for crown-of-thorns starfish, which are identified by their purplish hue and arm/thorn morphologies, along a preprogrammed course.
6At night, when starfish are more active and swimming is prohibited, the bot can operate.
6It can also work in bad weather and high currents, and it’s programmed to recognize certain hiding spots for starfish.
6When a starfish is spotted, the echinoderm lowers its arm and injects 10 milliliters of deadly bile salts into the starfish, effectively digesting it from the inside.
6Bile salts have recently taken over as the preferred toxin from sodium bisulfate.
7 After weighing many choices, experts determined that injecting 10 mL of 8 g l1 Bile Salts No. 3 coupled with 12 g l1 Oxgall solution is the most efficient and effective technique to kill these predators. 7Within 24 hours following injection, the starfish will die, eliminating the possibility of separation and regeneration. 6,7
The Great Barrier Reef’s survival depends on efforts to limit and control the population of crown-of-thorns starfish.
The Great Barrier Reef is a UNESCO World Heritage Site and a major tourist attraction in Australia.
3,5While efforts have been largely successful thus far, additional work and research is needed to ensure the reef’s ability to recover lost corals.
How many crown-of-thorns starfish are in the Great Barrier Reef?
There are already more than five million crown-of-thorns starfish on the reefs between Cooktown and Cairns, and as the outbreak extends south along the Reef, similar numbers will occur further south in the coming years.
Are crown-of-thorns starfish are mostly diurnal or nocturnal?
The Crown of Thorns Starfish, Acanthaster planci, is a species of starfish. This sea star has caused widespread worry throughout the world, notably in the South Pacific. Crown of thorns outbreaks have occurred every thirteen years on the Great Barrier Reef since they were first found earlier this century. When starfish in these plague proportions enter a reef habitat, they feed so extensively on corals that they can entirely destroy a reef.
Scientists are still debating whether these outbreaks are a natural occurrence or the result of human influences. It’s possible that these outbreaks are the result of extra nutrients entering the water from land-based sources like agriculture and waste management.
Interesting Facts
- The Red Sea, Indian Ocean, and Pacific Ocean are home to the Crown of Thorns.
- The second largest sea star, behind the Giant Sunstar, is the Crown of Thorns.
Why do crown-of-thorns starfish eat coral?
COTS are a vital part of the ecology on healthy coral reefs when present in large quantities. They devour the faster-growing corals, allowing the slower-growing species to catch up and increase the coral diversity of our reefs. The impact on coral reefs, however, can be fatal if the coral-eating starfish appears in large numbers.
How can the crown-of-thorns starfish be controlled?
As part of the Marine Park Authority’s Crown-of-thorns Starfish Strategic Management Framework, the Crown-of-thorns Starfish Control Program was formed in 2012 and provides a tactical reaction to outbreaks.
The method employs dedicated vessels with highly trained crews to hand cull starfish using bile salts or household vinegar as a deadly injection. The Crown-of-thorns Starfish Control Program also includes strategic surveillance and monitoring efforts. This ensures that culling efforts are focused on the areas that will provide the most benefit, that progress is tracked, and that pest control outcomes are maintained once they have been reached.
Supporting the environment and Reef communities
The Crown-of-thorns Starfish Control Program provides social and economic benefits to Australians in addition to environmental benefits for the Great Barrier Reef’s health. The program has been delivered in collaboration with the Reef tourism industry through the Association of Marine Park Tourism Operators since its inception (AMPTO). The reef is kept healthy in areas where local tourism firms send their national and international customers to experience the Great Barrier Reef through targeted crown-of-thorns starfish control. More than 100 people, mostly from Queensland, are trained and employed as part of the initiative.
Program growth and funding
At first, the program only had one or two dedicated ships. However, the outbreak that started in the northern management region in 2010 migrated south over time. The Crown-of-thorns Starfish Control Program received more money in 2018. In 2018-19, the program was able to expand from two to six vessels thanks to the additional funding. The expansion of the program allowed for the first time the deployment of crown-of-thorns starfish control vessels in the Marine Park’s far north and far south.
Five crown-of-thorns starfish control vessels have been deployed in the Marine Park’s northern, central, and southern management districts as of 2019-20. Control activities are deliberately tailored within each management region to focus on reefs of high ecological and economic value.
Since 2012, the Australian government has been funding the Crown-of-thorns Starfish Control Program. The Reef Trust Partnership (RTP) between the Great Barrier Reef Foundation (GBRF) and the Department of Agriculture, Water and the Environment provided funding for the Program in 2019-20. (DAWE). The GBRF and the DAWE have fully supported it through the RTP for 2020-22. The GBRF, the Great Barrier Reef Marine Park Authority (the Marine Park Authority), and the Reef and Rainforest Research Centre have formed a strategic collaboration to deliver the Program’s manual in-water control component (RRRC).