Starfish Swarm Devouring Corals in Indonesia

Dave Hansford, National Geographic News 17 Jan 08;

"Reefs can cope with periodic disturbances if they are healthy. If they've got good fish populations, good water quality, and good coral, they can bounce back within 10 to 15 years."

Predatory starfish are swarming over one of the world's most diverse coral reef ecosystems, researchers announced, threatening the health of reefs throughout the Indo-Pacific region.

Crown-of-thorns starfish, named for the long spines covering their bodies, feed on corals by spreading their stomachs over the animals living inside, then secreting enzymes that liquefy the corals' tissue.

"They prefer certain species and take them first, then they'll eat the others later," said Alison Green, a marine scientist with the nonprofit Nature Conservancy.

The starfish are found naturally throughout the Indo-Pacific. But a recent survey of reefs off the Indonesian island of Halmahera revealed that the numbers of the predators in some areas are double those that exist in a healthy reef.

Halmahera, the largest island in Indonesia's Maluku group, lies within the "coral triangle," which has been described as a global center of marine biodiversity.

The triangle spans eastern Indonesia, parts of Malaysia, the Philippines, Papua New Guinea, Timor, and the Solomon Islands (see a map of the region).

The localized starfish outbreak, experts say, could be an early warning of more widespread reef decline.

"Imagine the most beautiful coral reef with lots of three-dimensional structure, lots of color, and lots of fish," Green said.

"Then [imagine] the same place, except that it is dead, covered in black algae, and the fish are gone. Crown-of-thorns can do that."

Huge Outbreak

Andrew Baird is a scientist with the Australian Research Council's (ARC) Centre of Excellence for Coral Reef Studies and James Cook University.

He was part of the starfish survey team, jointly led by the ARC center and the New York-based Wildlife Conservation Society.

The team found between 300 and 400 crown-of-thorns starfish within a hectare (2.5 acres) of reef around Halmahera, Baird said.

"On [Australia's] Great Barrier Reef, we define an outbreak as 200 animals per hectare," Baird said.

High nutrient levels due to agricultural fertilizer runoff were most likely responsible for the population boom, he added.

"It stimulates blooms of microalgae—plankton—and the larvae of the crown-of-thorns starfish, under those conditions, survive very well," he said.

"In normal years, perhaps one in a million [starfish larvae] might survive. In one of these years, maybe a hundred in a million survive. You get huge recruitment."

Overfishing of the starfish's natural predators, such as triggerfish and the giant triton mollusk, likely worsened the situation.

Survey teams also found evidence of reef blasting—a practice that uses explosives to stun fish or collect coral as construction material.

"A lot of people rely on the reefs for their livelihood and their food. Without healthy reefs, it could result in serious economic hardship," Baird said.

(Related news: "Coral Reefs Vanishing Faster Than Rain Forests" [August 7, 2007].)

Bounce Back

For now, the experts noted, certain species on the reef show healthy enough populations that the ecosystem could recover.

"I think the answer lies in good management to prevent the outbreaks in the first place," the Nature Conservancy's Green said.

"We need to be particularly careful about how we manage the land and fisheries in those areas."

A network of marine protected areas, she said, combined with land-use and fisheries reforms, would ensure the survival of the coral triangle.

"Reefs can cope with periodic disturbances if they are healthy. If they've got good fish populations, good water quality, and good coral, they can bounce back within 10 to 15 years."

Coral reefs threatened by flesh-eating starfish
Paul Eccleston, The Telegraph 17 Jan 08;

One of the world's richest and most precious coral reef systems is under threat from a voracious predator.

The notorious Crown of thorns starfish has been found in large numbers by scientists in Halmahera, Indonesia, at the heart of the so-called 'Coral Triangle', which lies between Indonesia, Malaysia, the Philippines, Papua New Guinea and the Solomon Islands.

It is regarded as the jewel in the crown of coral reef biodiversity and is considered the genetic fountainhead for coral diversity found on Australia's Great Barrier Reef, Ningaloo and other reefs in the region.

The starfish eats the delicate coral polyps which form the thin film of flesh on the outside of the coral skeleton.

After attaching itself it spreads its stomach over the coral and releases a flood of digestive juices. The polyp flesh is liquified and then absorbed by the starfish. When it has cleaned the coral of flesh it moves on leaving behind just the calcium carbonate skeleton.

Scientists think the outbreak may have been caused by the poor quality of the water and could be an early warning of widespread reef decline.

Surveys of Halmahera by the Bronx Zoo-based Wildlife Conservation Society and ARC Centre of Excellence for Coral Reef Studies confirmed that while its reefs are still 30-50 per cent richer than those nearby, some areas were almost completely destroyed.
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"The main cause of damage to the corals was the Crown of thorns starfish," Dr Andrew Baird of the ARC Centre of Excellence for Coral Reef Studies and James Cook University.

"We witnessed a number of active outbreaks of this coral predator. There was little to suggest that the reefs have been much affected by climate change as yet: the threats appear far more localised."

The scientists found there were still healthy populations of certain species around the reefs and believe there is still time to reverse the damage.

"The good news is that the reef fish assemblages are still in very good shape" said Tasrif Kartawijaya from WCS-IP.

"We saw Napoleon wrasse and bumphead parrot fish at almost every site. So these reefs have the capacity to recover if we can address the current threats."

As well as the damage caused by the starfish the survey found evidence of explosives being used for fishing during a break down of law and order following communal violence in 2000-2003.

In the same period many reef lagoons were mined of their corals for use in construction, an activity encouraged by the Indonesian military.

At the Climate Change Conference in Bali the Coral Triangle Initiative (CTI) was announced by six regional governments offering renewed hope for the reefs in the region but little detail was given of how the initiative would operate and whether research would play a central role.

"We are disappointed research is yet to be fully considered in the CTI. The success of large marine parks, like the Great Barrier Reef Marine Park, is largely due to the primary role science plays in understanding what's going on, so managers can make good decisions," said Dr Baird.

"It isn't enough just to document the diversity of the region. Large scale research is required to understand the Coral Triangle ecosystems and work out how best to respond to threats such as poor water quality and over exploitation," Dr Campbell added.

Coral reefs are the largest living structures on Earth, and there are more 4,000 species of reef fish, making coral reefs the home of a quarter of all fish species found on the planet. They are of enormous economic importance with 500m people depending on them for survival. They generate billions of pounds per year through tourism.

Coral reefs represent the most biologically diverse habitat on earth and are entirely self-sufficient generating and recycling all the nutrients they need but they are under serious threat with 10 per cent already dead and another 70 per cent threatened by human activity.

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