Corals: The Turn Of The Tide

Corals are dying but science could be able to help them fight back from the brink.

AsianScientist (Dec. 5, 2019) – Fully clad in a wet suit, eager divers dip their flippers into the cool and almost transparent water. They plunge down into the sea and instead of seeing a technicolor reef, they see endless fields of ghostly pale corals. They are looking at Okinawa’s natural coral reefs, of which at least half have been destroyed.

Aside from the ravaging effects of climate change, human factors such as unsustainable tourism, coastal developments and excessive fishing have aggravated Okinawa’s fragile coral ecosystem. Today, the Japanese prefecture is hard pressed for solutions.

Okinawa is found at the edge of The Coral Triangle, where three quarters of the entire world’s coral species lie. More than 500 million people around the world depend on coral reefs for food, income and coastal protection, according to the US National Oceanic and Atmospheric Administration.

Primed with state-of-the-art technology, committed researchers and proximity to one of the most diverse coral reefs in the world, Okinawa takes a multi-pronged approach of restoration, conservation and perhaps genetic modification to save its corals.

When it comes to coral farming, there are two applications that the locals turn to, namely land-based nurseries and ocean-based nurseries.

Land-based coral nurseries

He rolls up his sleeves, dips his hand into a double-bed-sized container and picks up a mundane-looking, palm-sized concrete block. Coral caretaker Shouhei Matsuzaki is holding on to the home of an Acropora coral.

These corals did not come from the ocean. Instead, coral polyps—which are like small upside-down jellyfish—are placed into small crevices on these cement blocks for cultivation. Every day for the past 17 years, he inspects and cultivates around 70 species of corals for the Okinawa Churaumi Aquarium. All of the corals cultivated are to be transplanted into the aquarium’s Coral Reef Tank, which houses 450 coral colonies.

This controlled environment mitigates natural risks like competing with other corals, the presence of natural predators like the crown-of-thorns starfish, boating and tourist damage, and exposure to warm sea waters that cause bleaching. Small fish in the containers creating gentle movement in the water also mimic the natural coral reef, said Matsuzaki.

“The Okinawa Churaumi Aquarium has an open water system which allows water to come and go into the ocean. Corals in the exhibition tank have been spawning annually for 15 or 16 years and the coral eggs will go into the ocean from the aquarium,” said Hiromi Yamamoto, a coral reef ecologist at Okinawa Churashima Foundation.

On July 2, 2002, approximately 300,000 coral larvae were released into the wild from the aquarium in an effort to re-establish the dwindling Acropora coral population. This experiment showed that captive-bred corals could still impact wild corals if they share the same ocean water system, said Yamamoto.

Ocean-based coral nurseries

That being said, it is not impossible for corals to be cultivated in its natural environment. Right off the coast of Onna Village, similar cement blocks with coral polyps are camouflaged in the natural coral reef. These corals, difficult to spot by the unobservant eye, are grown alongside the natural coral reef. Meanwhile, just a few minutes away lies an ocean-based coral farm, the Maeganeku Farm. Established in 1998, fishermen from the Onna Village Fisheries Cooperative cultivate Acropora on various metal structures to increase coral numbers.

An essential part of gauging the success of restoration works is to monitor coral health. Marine biologists Piera Biondi and Giovanni Masucci spend close to an hour underwater examining the vibrancy of the corals and collecting two buckets of rubble from the ocean floor. The rubble is surveyed for its diversity and quantity of organisms living on it; the more diverse and numerous the inhabitants, the healthier the reef. This laborious assessment process takes between six to ten hours each time.

Corals can reproduce both sexually and asexually. In the case of spawning in the Okinawa Churaumi Aquarium, some corals sexually reproduce through the fusing of coral eggs and sperm, in a process that happens only once a year. Alternatively, asexual reproduction occurs when corals break off and resettle elsewhere to start new coral clones, which eventually form a colony. This process, called fragmentation, is more popular with farmers as it restores the reefs faster, but at the cost of the reef’s genetic diversity.

“Restoration and transplanting costs US$20-30 per coral colony here in Okinawa, which includes all the farming, transport, work and monitoring expenses. At the Great Barrier Reef, it only costs a few cents,” Masucci said. He believes that costs expended on restoration is better spent on conservation efforts, which he feels Okinawa is lacking in.

Dr. James Reimer, a marine biologist at the University of Ryukyus, said that conservation of a site is six times more effective and six times cheaper than restoring a site. “Instead of focusing on reef restoration, the prefecture might want to preserve what is left,” Reimer said.

The challenges of conservation

A ‘kayaktivist’ pedals out to sea, holding placards and bumping his kayak against a construction site, while another local sings loudly about the beauty of Okinawa in front of a military base. This is how some of the locals protest against the expansion of a US military base at the Henoko district. The construction scheme aims to reclaim 33 hectares of land in Oura Bay, which houses 5,000 species of marine organisms.

Earlier in the year, Japanese prime minister Shinzo Abe gave orders to transplant rare corals out of the construction zone before land reclamation work began. “Coral reefs were transplanted before the sand and dirt were dumped in. To reduce the environmental burden as much as possible, endangered corals that had inhabited the beach were scooped up with the sand and transferred to another beach,” Abe said in a NHK program on January 6, 2019. Despite the Prime Minister’s statement, the protests still continued. The first Saturday of August 2019, which garnered over 800 supporters, was the 1,854th day of 24-hour protest outside of the Camp Schwab military base.

The Okinawa Defense Bureau plans to transplant some 39,000 coral colonies and has so far transplanted nine of them.

“The fact that 39,000 coral colonies have to be transplanted plainly indicates that base construction is destruction of the environment,” said Hideki Yoshikawa, director of the Okinawa Environmental Justice Project.

“The Okinawa Defense Bureau’s evaluation of the survivability of the nine colonies already transplanted is still at a preliminary stage, but even the nine transplanted are not guaranteed to survive as they have to face various challenges adapting to the new environments,” Yoshikawa added.

Genetically modified corals

It takes 15 to 25 years for reefs to recover from a major bleaching episode because of the slow rate at which corals grow. Even with conservation and restoration efforts carried out at full strength, all it takes is one heat wave to render all efforts useless. This was the case in Sekisei Lagoon, Japan’s largest coral reef. Half of Sekisei Lagoon’s reefs were destroyed in a bleaching episode in 2016, according to Japan’s environment ministry. The reef also faced another bout of bleaching in 2017, further diminishing recovery efforts.

However, not all hope is lost. Another radical intervention has been born—genetically modified ‘super corals.’ As different corals have different capabilities, the Acropora is often used to increase coral cover given that it is one of the fastest growing hard coral species.

Assistant Professor Huang Danwei, a researcher at the National University of Singapore, discovered that some corals found at more than eight meters in depth can survive with little light. This genetic trait could be helpful in creating resilient ‘super corals’ that can survive the impending rise in sea levels. Masucci also noted that physically massive and sub-massive corals are more typhoon-resistant, which is helpful in Okinawa, one of the most typhoon-prone prefectures in Japan.

Using a gene-editing tool called CRISPR-Cas9, a research team at Stanford University has managed to create genetically modified corals that are more resilient. Genetic engineering can be useful for creating corals with resilient traits, geoengineering the atmosphere to cool reefs down, or engineering reef-inhabiting algae to be more heat resistant. Thus, the discovery of genetic engineering opens up many new possibilities for altering the fate of corals.

An uncertain future

Despite all these various efforts, the outlook for the corals is pessimistic. Both Masucci and Yamamoto believe that it is possible for all coral reefs to be gone by 2100, save a few that are far from humans, sustainably managed, or individually resilient.

Corals date back to hundreds of millions of years ago and are found in the most extreme environments—they are perhaps more resilient than we think.

“I am positive that the reefs are not going to die, corals will survive, and will survive much longer than humans,” Reimer said. “But when we go down the tubes, we are going to take a lot of species and animals with us.”

If we have the power to destroy in a few decades what took millions of years to create, perhaps we have the power to reverse that too.

This article won third place at the 2019 Asian Scientist Writing Prize.

Click here to see photos of the the prize presentation ceremony held on December 4, 2019.


Copyright: Asian Scientist Magazine; Photo: Shutterstock.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

Amanda Bambby Cheuk is a student at Nanyang Technological University, Singapore.

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