Protecting Corals with Genetic Technology

The ocean is the source of life. And coral reefs in particular are known as the cradle of life. Despite covering only 0.1% of the Earth's surface, they are home to more than 90,000 species of organisms. Yet corals are now facing a serious crisis. Due to the effects of global warming and other factors, bleaching is occurring repeatedly. Corals are dying and biodiversity is being lost. One scientist is trying to solve this problem using genetic analysis technology. Biologist Sato Noriyuki decoded an entire coral genome. He is studying Miracle Coral, which happens to be resistant to bleaching. After analyzing its genes, he uncovered the secret behind that resistance. He is also using a custom-developed underwater drone to survey coral in deeper waters. By analyzing environmental DNA in seawater, he aims to support conservation efforts. Preventing coral bleaching and protecting biodiversity. We'll delve into the latest genetic research. The Okinawa main island is located approximately 1,500 kilometers southwest of Tokyo. Sato likes to stroll on this beach. However, even this beautiful coastline is facing the harsh reality of coral reef destruction. Numerous corals believed to have died from bleaching have washed up on the beach. Last year, in 2024, the temperature rose very high. The coral reefs disappeared in the shallow water here. There is a possibility that they will disappear. Sato belongs to the Okinawa Institute of Science and Technology. He conducts genetic research on marine organisms. He is working to decipher genomes and elucidate the mechanisms by which they adapt to their environment. Sato began his genome research in 2002. It all started when he was involved in sequencing the genome of the sea squirt. In 2011, he succeeded in decoding a coral's entire genome. This enabled research into bleaching phenomena and conservation at the genetic level. At that time, Sato read the genome of a coral in the Acropora genus. Acropora corals are known to die off easily due to bleaching. He discovered that Acropora corals are missing the CBS gene, which synthesizes amino acids. Sato believes that this is the reason why Acropora corals are prone to dying from bleaching. Sato is applying this genomic analysis technology to conservation activities. This is the Onna Village Fisheries Cooperative. Many fishermen have made their living from harvesting mozuku seaweed. However, they say that harvesting has declined since a certain point. This was triggered by large-scale coral bleaching that occurred in Okinawa's waters in 1998. Many corals in Onna Village also died off, resulting in the collapse of the ecosystem. Coral reefs are home to symbiotic phytoplankton called zooxanthellae, which produce nutrients through photosynthesis. However, when water temperatures rise, corals expel the zooxanthellae. This results in bleaching. If this bleaching continues for about a month, the corals will die from lack of nutrients. So the Fisheries Cooperative began cultivating corals to restore the ecosystem. The method involves breaking damaged corals into small pieces and planting each piece back in the sea. Like cuttings in a garden, the planted coral grows on its own, allowing for efficient propagation. However, this method has a drawback. Since these corals are clones with identical genes, rising sea temperatures mean they will all suffer damage and die at the same time. In Onna Village, the cultivated corals frequently bleached and died in large numbers. That's when Sato was consulted. A new cultivation method that didn't rely on cloning was needed. Sato analyzed the DNA of the farmed coral in Onna Village. He then developed a method to distinguish between cloned coral and non-cloned coral. Sato proposed a method of grouping three or more types of coral with different genes and planting them together. He reasoned that genetic diversity would make the corals more resilient to environmental changes, such as rising sea temperatures. The Fisheries Cooperative decided to manage the genetic information of individual corals and utilize it in their planting arrangements. This coral is number 58. Next to it is number 59. These are corals with different genes. Placing corals with different genes also had another effect. The probability of coral eggs and sperm fertilizing increased. Right next to the coral field were baby corals. As fertilized corals grow, they are expected to create further genetic diversity and lead to a coral reef that is resilient to environmental changes. I'm so happy that I can grow good corals. It's no big deal. I can tell because you taught me how to do it. There are many places in the world that grow coral, but this is the only place that grows corals while protecting the genetic background. There is no doubt that we are great at growing corals. Meanwhile, at another coral farm in Okinawa, something remarkable occurred. This is Kinjo Koji. He has been farming coral since 1998, when large-scale coral bleaching occurred in the waters around Okinawa. Kinjo discovered that some of the corals he was cultivating were resistant to bleaching. This coral is Acropora tenuous. Even as surrounding corals bleach, it retains the ability to survive. This coral was born through a method Kinjo developed from his years of experience in coral farming. I started experimenting with growing corals on the edge of the sea. I thought that if I didn't grow corals in a place where stress is applied, I wouldn't be able to compete with the current world. The method involves first cultivating coral in relatively cooler water temperatures. Any corals that survive bleaching are selected and moved to a slightly warmer water temperature. This process of selecting corals that survived and moving them closer to the surface was repeated. This led to the emergence of a coral that is resistant to bleaching, which Kinjo called Miracle Coral. Kinjo presented this phenomenon at the Japanese Coral Reef Society in 2017. Sato became interested. This coral can withstand up to 32 degrees. Sato decided to investigate why Acropora tenuous can withstand high sea temperatures. There are three types of Acropora tenuous, but Kinjo says that only the green type does not bleach. So Sato investigated the genes related to this color. He discovered that in the green type of coral, the gene responsible for producing the fluorescent protein GFP is highly active. Sato believes this is why Acropora tenuous is less prone to bleaching. Acropora tenuous is more and more active in the green coral, and is responsible for producing the fluorescent protein. This is why Acropora tenuous protects itself from UV rays. Sato suspects that the GFP gene activates the ability to absorb harmful ultraviolet rays, making the coral resistant to bleaching. We call this Miracle Coral, but we didn't grow it to make it resistant to high sea temperatures. At first? Yes, at first. But I think it has the potential to be able to be targeted. In 2021, Sato began a new study using DNA. This water scooped from the sea surface may look like ordinary seawater. Yet it contains a treasure trove of information about coral ecology. The seawater contains coral environmental DNA, or e-DNA. Corals release mucus and excrement, and DNA contained in these substances can be detected. Analyzing the collected DNA helps determine what types of coral are present. Sato conducted e-DNA surveys at 62 locations around Okinawa Main Island and created a coral database. Studying coral species and their habitats yields information he can use to protect and restore coral reefs. There are 62 coral reefs in Okinawa. If a coral eruption occurs and the water is scooped again, and most of the coral's environmental DNA is lost, we can determine if the coral is under the water. That's why it's a treasure trove. Sato is expanding the scope of e-DNA mapping through joint research with the University of the Ryukyus. Hi, Frederic-san. Good to see you. Hello. Very, very, hello. That's why you went there. Yeah. Heliopora. OK. This is Frederic Siniger, who studies corals at the university. Yesterday I collected some samples for you. Yeah. This is alveopora from 55 meters from deep. Frederic has high hopes for Sato's e-DNA research and often provides him with coral samples he has collected. In fact, Frederic is studying an area that is still largely unexplored in coral research. His wife, Harisaki, is also a researcher. The two observe corals while diving. Little research has been done on corals at depths of 30 to 150 meters since scientists thought the weak sunlight wouldn't support much coral growth. However, it has become clear that even in dim light, many corals actually thrive. Frederic and his team are photographing and analyzing the types and quantities of coral to study the diversity of corals in deeper water. They made a significant discovery in these waters in 2012. Seria topora hystrix is commonly found in shallow waters and is known for its distinctive spiky shape, making it popular among divers. However, many died off during the large-scale bleaching event in 1998, and it was believed to have gone extinct here. However, Hari and her husband discovered them at a depth of 40 meters. This was 14 years after the large-scale bleaching event. Hari believes that the survival of Seria topora hystrix in deep waters holds significant implications for the conservation of coral reefs. However, there are challenges to this research. At these depths, divers can only work for about 10 minutes per dive. That's why the two researchers are pinning their hopes on eDNA, At the moment, we are blind. You know, we just look on the map and, OK, let's go here and see what we find. So it's not the most efficient way. So this is why we need eDNA. Ah, OK, OK. Hopefully, eDNA map can maybe help a lot to target. Sato is now attempting to create a map of coral eDNA even in deeper waters. And he has a powerful tool, an underwater drone capable of diving down to 300 meters. It is equipped with two capsules that collect seawater containing eDNA. Today, he is investigating some deep waters off Miyagi Island, east of Okinawa, which have never been examined before. This footage of the seabed at 55 meters shows soft corals, a type of coral unique to deeper water. We can see how densely they are clustered. There are so many soft corals. There are so many types of soft corals. I don't know how far I can go. It hurts. Sato decided to proceed to a deeper area. At 83 meters, this spot is about 30 meters deeper than before. Various corals are also visible on this seabed. However, since the distribution of corals cannot be confirmed just by looking at the screen, it is necessary to collect eDNA. I found a hard-looking one. I don't know if the hard corals will come out from the environmental DNA. I can't tell just by looking at it. Okay, I'll take the water. I'll take the water. What kind of coral eDNA will he find? Another sample for the new eDNA map has been collected. I'm desperate now. I want to record how the coral looks like as a whole in Okinawa. I want everyone to understand that this kind of change is happening in the most important coral reef in the sea. We can see what's happening on land, but we can't see what's happening in the sea, so we don't know. I think coral reefs are telling us that amazing things are happening in the sea. Using DNA technology to protect and nurture corals that survive in harsh environments, Sato's challenge continues.