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Post by Andrey Braga

Let’s dive deep into one of the oceans’ enigmas. The crown-of-thorns starfish (Acanthaster planci), a spiky elegant creature equipped with up to 21 arms, emerges as a villain in many coral reef’s sad stories, but it is actually part of the natural balance of these ecosystems.

What are Crown-of-Thorns?

The Crown-of-Thorns is one of the largest starfish in the world, ranging in size up to 40 cm. Their primary diet consists of coral polyps and as adults are able to consume up to 10 m2 of coral a year. This sea star plays an important role in coral reefs ecological succession, since they tend to prefer feeding on faster growing corals, slower-growing corals are able to form colonies, increasing coral biodiversity.

What do they eat and how?

They extend their stomach onto the surface of corals. The dissolved nutrients resulting from the digestion of coral’s soft tissues are absorbed directly into their stomach walls, leaving the skeleton part behind.

Their habit of feeding on coral wouldn’t be a major issue for the reef, if it wasn’t for a combination of factors that already increases the level of stress in which corals are found, making them more vulnerable and negatively impacting its health.

They include, but are not limited to, changes in water temperatures, ocean acidification, pollution, episodes of Crown-of-thorns outbreak and their lack of predators due to overfishing.

A Crown Of Thorns Starfish, A Predator Of Coral, Moves Across A Diverse Coral Reef Ecosystem In The Maldives

A crown of thorns starfish, a predator of coral, moves across a diverse coral reef ecosystem in the Maldives

The stark contrast between a spiky crown of thorns starfish and the delicate coral reef in the Maldives highlights the complex and challenging environment beneath the waves

Which factors are related to the Crown-of-Thorns outbreak?

Crown-of-thorns starfish have boom-and-bust population cycles, where all of a sudden there can be a huge surge of this species. This is mostly related to larval survival rate, which unlike corals, have an increase in probability of survival with warmer sea levels.

Human activities, such as overfishing of their natural predators also contributes to it. Due to the fact that Crown-of-thorns has a toxin called saponins in their spines and tissues, not many animals find them appetizing.

One of the main ones is the Giant Triton that can eat about one spiky starfish a week and just their presence might make Crown-of-thorns avoid a certain area. Unfortunately, their shell attracts collectors making them less abundant in the reef. Other examples are the Stellate Pufferfish and the Titan Trigger Fish.

A Scuba Diver Swims Alongside A Crown Of Thorns Starfish On A Colorful Coral Reef In The Maldives.

Underwater Crown: A Thorny Intruder on the Maldivian Reef

A scuba diver swims alongside a crown of thorns starfish on a colorful coral reef in the Maldives

Innovative solutions and human intervention

With the lack of natural predators, humans started intervening as well, especially in areas where their presence is more harmful around the world. Top tech inventions, such as underwater drones injecting a solution that kills the starfish, are already in use. It is important to mention that this substance doesn’t harm the animal that consumes its carcass. Another option, which is simple but less effective, is manually removing them from the reef.

Marine Marvels of the Maldives

This and many other fascinating animals can be found both in day and night dives and snorkel trips in the Maldives, representing the biodiversity of animals that are found there.

From the biggest fish in the planet, the whale shark, and the majestic mantas, to mammals like dolphins, cephalopods such as octopus, all the way to echinoderms as the crown-of-thorns Starfish, the Maldives is an underwater paradise that should definitely be on the top of your bucket list for some well-deserved holiday.