Filipino marine scientist discovers technique to raise corals faster

A Philippine scientist claims to have found a faster way to raise an endangered coral in the open sea and potentially avert its extinction decades from now. 

If successfully replicated on other species and in other environments, the technique discovered by marine scientist Charlon Ligson could help save coral reefs – which studies said could go extinct in 70 years – and slow the impact of climate change and global food security.

“[I]t will buy time for our corals while global leaders make some drastic moves to really cut carbon emissions that are the main drivers of this chaos,” Ligson, a student at the University of the Philippines Marine Science Institute, told BenarNews.

Ligson co-authored a study published in 2021 that centered on Staghorns or Acropora Verweyi – a specific type of coral – which found that they were in rapid decline.

Titled “Survival and sexual maturity of sexually propagated Acropora Verweyi corals 4 years after outplantation,” it is one of the first studies that “followed outplanted corals to maturity.”

Outplanting is when tiny corals raised in nurseries are transferred into the wild or reefs.

The main goal of the research was to determine if the staghorns outplanted at a smaller size can last for years and if they could become sexually mature enough to propagate on their own in the wild. Ligson said most coral reef restoration monitoring efforts last only for a year or two.

“Our record of 18% after four years is considered good as compared to those with survival records after at least two years of outplantation. Some coral babies from previous projects may not even reach four years, or worse did not even have records at all,” he said.

Outplantation can be likened to an underwater version of tree planting.

Conservation group Reef Resilience Network defines it as “a crucial step in coral gardening efforts, where corals are transported from nurseries and secured back onto reef habitats.” It is a labor-intensive procedure that often requires restorers to use scuba gear.

In 2015, Ligson had an idea: “What if I outplant the Acropora in just four months?”

He went to Cabungan and Caniogan towns in Anda, Pangasinan province, to release 240 coral babies in two different size classes: 1.0 to 1.5 cm and 0.3 to 0.5 cm in diameter.

Feared ‘babies’ were dead

But this study that “challenged the norm” would take four years before it got answers.

Initially, Ligson did not intend to check results because of budgetary constraints. Biases for traditional procedures on acropora outplantation also led Ligson to believe that his “babies” were already dead.

In 2019, he accidentally ran out of species to write about for a new paper, which made him go back and check on his old project.

He found that some of his outplanted corals had survived.

“I was shouting underwater when we found them. I couldn’t believe it,” Ligson said, adding that the corals survived despite “regular disturbances to these reefs such as typhoons and coral bleaching events.”

 About 18% or 43 of the 240 survived. Of those, 35 are sexually matured and pregnant, giving Ligson confidence that they can multiply on their own in the wild and rebuild degraded coral communities.

There were no significant differences between the small and large coral outplants in Cabungan, where 19 coral babies sexually matured. Ligson said they grew to a similar size after four years.

But in Caniogan, where water has greater turbidity, size played a major role. Larger outplants had a higher survivorship than their smaller counterparts.

“It is more important to choose the right site,” he said.

Found in warm and tropical waters, coral reefs are home to millions of species that are key to food production and sources of livelihood. The corals release nutrients consumed by bacteria and small organisms which are then consumed by larger organisms.

Coastal communities and island nations like the Philippines depend highly on them.

Although often confused for rocks, corals are the longest living animals in the world. They are more primitive than dinosaurs.

Ligson acknowledged that his findings are limited to a single species in specific areas, but he said they can help open new windows in coral rehabilitation efforts. The success could ramp up efforts to repair reefs while reducing government expenses that come with raising corals.