Coral killers face the bitter end

James Cook University’s Dr Lisa Boström-Einarsson led a large-scale assessment using vinegar to inject CoTS at four sites on the reef over six weeks.

Dr Boström-Einarsson and her co-authors had previously shown that the simple household chemical was just as effective at killing the reef-eating starfish as much more expensive chemicals with complicated processes.

She said the latest tests, in collaboration with the Great Barrier Reef Marine Park Authority (GBRMPA) and the Association of Marine Park Tourism Operators (AMPTO), show vinegar has no ill-effect on other organisms in the sea.

“We recorded live coral cover, abundance of coral disease, fish abundance and diversity, fish diseases and the abundance of closely related invertebrates before, during and after the six-week study period and found no detrimental effects,” she said.

Dr Boström-Einarsson said CoTS are breeding at epidemic levels and are one of the primary reasons for the decline in live coral.

“There are millions of starfish on the Great Barrier Reef and each female produces around 65 million eggs in a single breeding season. It would take a massive effort to try and cull them all individually, but we know that sustained efforts can save individual reefs.”

The Great Barrier Reef has been exposed to multiple disturbance events in recent years, including the 2016 and 2017 mass coral bleaching, three severe tropical cyclones in the past three years, and the ongoing CoTS outbreak.

“Given the diverse range of disturbances that are currently affecting the reef, we need to give it the best possible chance to recover,” she said.

The safety of vinegar had previously been assessed in an aquarium setting where species known to feed on or associate with CoTS were placed in a tank with starfish injected with vinegar. This study confirms the previous findings that the weak acetic acid in vinegar is quickly diluted on the reef and poses no threat to other marine organisms.

All injected CoTS die within 48 hours.

Fred Nucifora, Great Barrier Reef Marine Park Authority Director of Tourism and Stewardship, said the organisation is targeting those reefs identified as having high conservation and tourism values. “Culling crown-of-thorns starfish is a critical management activity to protect coral cover and boost Reef resilience, particularly in the wake of coral bleaching,” he said.

Dr Boström-Einarsson said method is also widely applicable to remote communities and developing countries where access to bile salts, the current substance used to kill CoTS, is limited.

GBRMPA has now added vinegar to their list of approved control chemicals, which means that operators can apply for permits to start controlling CoTS using the method.

The study was conducted with support from GBRMPA, AMPTO and the Reef and Rainforest Research Centre, and funded by the Ian Potter Foundation 50th Anniversary COTS Control Grant from the Australian Museum’s Lizard Island Research Station (LIRS) and the Great Barrier Reef Research fund, supported by the Great Barrier Reef Marathon Festival.

Dr Boström-Einarsson will be at Reef HQ in Townsville at 11am Thursday 26 April, 2017 with Mr Nucifora and Paul Crocombe – CoTS control permit holder. Examples of CoTS will be available for viewing onsite.

Images: available here.