But overfishing, pollution and climate change are responsible for making these habitats drastically negative. Especially in the world’s largest coral reef, the Great Barrier Reef, the tracks are clearly visible, but above all by side effects of the actual changes.
One of these concomitants is a rather hungry colleague, who over millions of times descends the reefs in shorter and shorter distances: The Crown of Thorns (COT). With a size of up to 40 cm in diameter and equipped with 6 to 23 arms, it is one of the larger starfish species (for comparison: the largest starfish Pycnopodia helianthoides or in English Sunflower Sea Star can reach 1 m diameter).
The crown of thorns you may not come too close but not only because of its size, but mainly because of its up to 5 cm long poison spines.
He has few enemies, and one of them is particularly popular with tourists as souvenirs from their holidays: the Tritonshorn, a snail with a very beautiful snail shell that everyone has probably ever seen.
Just never in the sea. In Malaysia, for example, for years, no more were found under water, which explains the explosive occurrence of thorn crown starfish.
But the overfishing and habitat destruction of other predators, such as the white-spotted puffer fish and the giant triggerfish, give the starfish a carefree life.
But why exactly is he so unpopular? As already mentioned, he is tall and hungry. His favorite dishes are only stony corals, which in the formation of coral reefs are something like the framework, because they produce the lime that forms the reef structures.
The nocturnal crown of thorns in a single night can kill about the size of its body in a single night. That’s about 13 cubic meters of coral surface per year.
Nature works flawlessly without our intervention. Everything is so well balanced that there are no imbalances. A balanced number of thorn crown stars.
Has a positive effect on the coral system, as it prevents some fast-growing corals from being contained, giving slower-growing corals the chance to thrive.
But when man intervenes in this balance, it is difficult, if not impossible, for nature to put this chaos back in balance.
Once the ecosystem is disturbed by drastically reducing one species, uncontrolled propagation of another species occurs. Thorn crown stars are known as “outbreaks”, in which, in the worst case, up to 1,000 animals per hectare occur.
One can certainly imagine the extent of the destruction. What a single starfish dies in a year takes decades to regrow. Or centuries. In addition, a crown of thorns for a starfish with 20 m per hour is quite fast.
So let’s summarize: Big, fast, poisonous and greedy. What do we do about it?
Once an area has been invaded by Crown of Thorns stars, swift action is required. I visited the island of Tioman in the South China Sea off the east coast of Malaysia, which a few decades ago still suffered greatly from the voracious starfish. And the situation today? Significantly more relaxed.
The reason for this is active marine conservation, which is operated on the island of Tioman. Because the need was out of the question: no coral reef means fewer tourists.
And that would be a serious problem for an island where 80 percent of its inhabitants work in tourism. Active Marine Conservation is controlled by two projects: GreenFins (www.greenfins.net/en/location/malaysia) and AWARE (www.projectaware.org).
For the concrete implementation but every single one is in demand, namely mainly divers and diving tourists. That’s why most of the dive centers have been trained on Tioman, how they can observe the coral reefs, document their changes or defend themselves against the frequent occurrence of enemies, such as the Crown of Thorns.
I wanted to know what the active “fight” against the gluttonous starfish looks like, and I met with the staff and operators of the B & J Diving Center to talk about the topic. According to them, two methods are used worldwide to contain the crown of thorns: Either they catch them with a hook from the corals, collect them in a large net and later infuse them with fresh water, which kills them immediately.
Or one injects vinegar into it several times, whereby they first become motionless and then die. On Tioman is mainly worked with the injection. One has to imagine the device as a long-tube glue gun, passing the spikes to inject the vinegar.
This is repeated in several places on the body, unless you use other chemicals that work faster (such as bile acid). However, vinegar is much easier to obtain on the island.
The divers told me that they get active when they discover more than 5 starfish at a dive spot during a normal dive during the day.
Because the invertebrates hide very well during the day, one can assume that once again three or four times as many of them are under corals and rocks.
During their last “cleanup” in July 2018, they discovered and rendered harmless about 50-60 crowns of thorns on less frequented dive sites at Tioman.
It is important that the diving schools communicate with each other and with the leading marine conservation organizations. Only then can timely action and an “Outbreak” be prevented.
The thorn crown stars are therefore no longer a major problem of the island, which unfortunately does not mean that there are no more problems.
Illegal fishing and plastic in the water are so-called permanent sites. Nevertheless, Tioman is currently the only island in Malaysia that has an improvement in its coral reefs.
Once some understanding of the importance of healthy coral reefs has arrived at each one, preventive action and active marine conservation work well – to the benefit of all involved.
Many thanks to Caro Joos (B & J Diving Center) for the picture impressions in this article.
Another interesting report: The Hard Childhood of Sea Turtles