Rapid Sea Urchin Die Off Baffles Cook Islands Marine Experts

Fears that depopulation could cause algae bloom in Avarua harbor

By Rashneel Kumar 

RAROTONGA, Cook Islands (Cook Islands News, Oct. 17, 2016) – The rapid die-off of sea urchins in the waters near Avarua area is causing a grave concern to local marine experts who are predicting an ultimate marine disaster from the problem in Rarotonga.

Scuba divers have recently observed an increase in the number of dead sea urchins within Rarotonga’s waters and further investigation has revealed that Vana (Echinothrix diadema) have been found to be losing their spines and dying off at Avarua Harbour.

Marine expert and Cook Islands Climate Change adviser Doctor Teina Rongo said investigators were baffled with the number of dead sea urchins washing up the shores near Avarua.

In the recent decade, he said sea urchins have proven to be an important herbivore on the reef and their rapid decline could cause a possible algal bloom in the waters surrounding Rarotonga.

Algal bloom is already an issue for the tourism industry with the recent rise in the unsightly weed at Muri lagoon, considered one of the top tourist spots in the country.

“Sea urchins are important grazers on the reef. They remove the sea weed, allowing corals to grow which is important for our reefs,” Rongo, who holds a PhD in Marine Biology, said.

“This problem occurred in the Caribbean in 1980s and it took 13 months for the disease to spread from Panama throughout the Caribbean.

“The consequence of this was a setback to the reef community of a Caribbean from a coral-dominated to an algal-dominated system. Till this day, these reefs of the Caribbean have not recovered.

“Therefore, the die-off of sea urchins is not good for us. We can’t afford to face a similar consequence.”

While research and studies are being conducted to find the origins of the problem, Rongo said the most likely cause of this die-off was pathogenic.

Pathogens include viruses, bacteria, and other types of germs that causes disease.

Rongo said they suspect the die-off could be because of a water-borne pathogen.

 “It's been a couple of weeks now that we have noticed the sharp increase in the dead sea urchins in the surrounding waters, especially around town area.”

“Right now we are looking into it and working with some experts from overseas to find the reason behind this problem.

“This species of sea urchins known as Echinothrix diadema is widely spread in our reef and also on the ocean fore reef. Known locally as Vana, they are also consumed by the people.”

Rongo is asking the community not to eat Vana until further notice due to a possible health hazard.

“Most of the marine problems such as fish poisoning and other outbreaks tend to occur in the town area first and then it spreads. There is a possibility of a similar scenario in this case as well.

“Our other concern is this spreading to the outer islands, if the problem is not already there. We don’t know the extent of this problem yet.

“Sea urchins are important grazers in the Pa Enua (islands) and their numbers have increased recently due to the decline of herbivorous fish in general. So sea urchins have taken up that important role of bush cutters of the reef.”

The Climate Change Cook Islands Division said it had made this case top priority to allow its reefs and citizens to be as safe and healthy as possible.

Cook Islands News
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