"Usually, an oxygen cylinder can be used for 40 minutes to 1 and a half hours, but when doing such a hard job as 'undersea hammering', a bottle of oxygen can be exhausted in 20 minutes."
The first episode of CCTV's "Homeland: China with Biodiversity" shows the scene of Zhang Yuyang's team at the South China Sea Institute of Oceanology of the Chinese Academy of Sciences "planting corals" on the seabed. Working at the bottom of the sea is difficult and even dangerous. But Zhang Yuyang did not flinch, he said, "With me, we can't let this sea become a 'dead sea'."
How bad is the current state of the reef? What kind of efforts has Teacher Zhang Yuyang's team made to change this situation?
The coral reefs on which 500 million people around the world depend are turning into white cemeteries
In May 2018, the state of Hawaii issued a ban on certain sunscreen products in hopes of saving Hawaii's endangered coral reefs.
Some people may not understand, don't I just put some sunscreen on? As for? Is it necessary?
I would like to talk about the results of the study and my personal experience, and I hope that you can understand the difficult situation of corals (if not specifically stated, the corals referred to here are reef-building stony corals) and attach importance to the protection of corals.
| A coral reef facing the crisis of the century
When it comes to coral reefs, the most well-known is probably the Australian Great Barrier Reef.
As can be seen from photos and videos, many of the Great Barrier Reef's colorful coral reefs have been turned into coral "cemeteries" with only white skeletons left.
The beauty of the Corals of the Great Barrier Reef (Image: https://speed.ettoday.net/news/901909)
Nearly two-thirds of the Great Barrier Reef corals have bleached after global warming (Credit: https://speed.ettoday.net/news/901909)
The world's most famous coral reef has suffered from the continued effects of rising seawater, with successive coral bleaching events in 2016 and 2017. In 2016, rising seawater caused more than 26% and 67% of coral deaths in the far north and north of the Great Barrier Reef. Coral mortality in the central and southern Great Barrier Reefs was relatively low in 2016, although they did not escape, with bleaching worsening in 2017 and a greater impact on the central region (ARC Centre of Excellence for Coral Reef Studies).
ARC Centre of Excellence for Coral Reef Studies
Coral bleaching of the Great Barrier Reef in 2016 occurred mainly in the north, with less coral bleaching in the central and southern parts (Image: https://www.aims.gov.au/)
Coral bleaching in the Great Barrier Reef in 2017 occurred mainly in the middle of the higher dimension compared to the previous year
（图片来源：ARC Centre of Exc ellence for Coral Reef Studies）
In the documentary "Chasing Coral", the bleaching of corals in the Great Barrier Reef is also visually shown, and the white, pink or purple corals seen in the air are nearing death, and the record of the World Coral Reef Congress at the end of the film and the status report from coral reefs around the world reveal that coral reefs face the threat of bleaching caused by warming seawater around the world.
| Why does rising seawater cause such a serious bleaching problem?
This starts with the environment in which corals grow.
Coral reefs are mainly distributed in the isothermal line of 20 °C in the average temperature of the sea water in the northern and southern hemispheres, which is due to the fact that the reef-forming reef-forming stony corals have strict requirements for seawater water temperature, and the suitable water temperature for most reef-building stony corals is 18-29 °C.
Zoom in, we can see the tentacles and mouths of the polyps (Image source: Visual China)
Both too low and too high water temperatures can cause bleaching and death of reef-building corals.
Because reef-building corals rely on the photosynthesis of symbiotic cordycephalus in vivo to provide energy for them, most reef-building corals live in shallow seawater at depths of 50 meters, but some non-reef-building corals that are symbiotic without insecticides can live at depths of hundreds or even thousands of meters.
It is precisely because of the symbiotic system of zooxanthellae and polyps that the survival and growth of corals are maintained. But the system is fragile, when the sea temperature rises above the normal temperature of 3-4 ° C, the coral and the good partner of zooxanthellae will turn their faces, zooxanthellae will leave the polyp, and the coral will starve to death due to lack of energy for zooxanthellae.
In addition to temperature and depth, the salinity of seawater, nutrient content in the water body, sediment and other factors will affect the distribution of reef-building corals, so to form a coral reef is to meet many environmental conditions, which is why in such a vast ocean, coral reefs occupy less than 0.2% of the area.
But don't underestimate this 0.2% area, which supports a quarter of the marine life species, nearly a third of the marine fish live in it, also known as the "tropical rainforest" in the ocean.
"Tropical Rainforest" in the Ocean (Image: Visual China)
In addition to bleaching, coral reefs are constantly threatened by overfishing, pollution, coastal engineering damage, seawater acidification, sea level rise, coral disease, and starfish outbreaks.
Long-spined starfish (Image source: Visual China)
| The sad current state of our coral reefs
Take the situation in my country as an example.
The Coral Biology and Coral Reef Ecology Discipline Group of the South China Sea Institute of Oceanography, Chinese Academy of Sciences, in collaboration with the Arc Centre of Excellence for Coral Reef Studies in Australia, reported on the changes in coral reefs in China for more than half a century.
As of 2010, the coral reefs along the coasts of Guangdong, Guangxi and Hainan in China have lost 80% of the reef-building coral population in the past 30 years due to human activities and pollution; although the coral islands and reefs in the South China Sea have not been affected by pollution, the average coral coverage rate has dropped from 60% to about 20% in the past 10-15 years due to overfishing of fisheries and the outbreak of long-spined starfish.
In the course of working on coral reefs, I have experienced this painful change first-hand.
In 2009, I participated in the Paracel Reef Survey Voyage of the Coral Biology and Coral Reef Ecology Discipline Group and conducted the first dive of my scientific career.
Since I grew up in the book, I saw the "beautiful and rich Paracel Islands", and although I was engaged in the research of coral reef ecology, the Photos of the Xisha Survey (taken from 2006) seen in the research group were also full of vibrant coral reefs, so before I went into the water, all I imagined was endless beauty.
However, the greater the expectation, the greater the disappointment.
When you see only a piece of dead coral skeleton under the water remaining on the coral reef, and there is no "fish" smoke around, the taste is indescribably uncomfortable, which is tantamount to a blow to the head.
Wandering in a dead silence and desolation, looking at the coral skeletons in his eyes, the shock in his heart was gradually replaced by doubt.
Why did the coral reefs of the Paracels become so desolate in a few years, and how did the "rich and beautiful" Paracel Islands disappear?
It wasn't until the end of the voyage, when we saw flocks of long-spined starfish on the coral reefs of the Western Sands, that we understood the culprits.
That was also the first time I had seen an outbreak of long-spined starfish and their destruction of coral reefs like a plague of locusts.
In 2006, the Paracel reef was still thriving, with various corals taking on different shapes underwater (Credit: Institute of South China Sea Research, Chinese Academy of Sciences)
In 2009, many corals were left with only skeletons, and calcium carbonate skeletons gradually collapsed under seawater and biological erosion (Credit: South China Sea Research Institute, Chinese Academy of Sciences)
| What happens if the reef disappears?
Globally, more than half of coral reefs are already severely degraded, but the more serious problem is that the rate of coral reef degradation will accelerate in the future.
If humans do not take any salvage measures, coral reef ecosystems could disappear from the earth by the end of this century at the current rate of degradation.
What are the impacts of the disappearance of coral reefs on humans?
Some people say that there is no impact, at most there are fewer tourist attractions, after all, there are not many people living near coral reefs.
This perception is truly wrong.
In fact, 500 million people around the world rely on coral reefs for food, feed their families from coral reef fisheries, engage in coral reef tourism, and rely on coral reefs to protect their homes. Without coral reefs, they will lose jobs, incomes and even struggle to get enough food to survive.
Globally, coral reefs provide $2.7 trillion worth of services to humans, including fisheries, tourism, coastal protection, maintaining biodiversity, pharmaceutical development, education and more (https://www.iyor2018.org/about-coral-reefs/benefits-of-coral-reefs/).
In addition, coral reefs are also closely related to national territory and sovereignty, and many territorial sea base points are islands formed by coral reefs, such as the territorial sea base points of China's Paracel Islands are coral islands and reefs.
If coral reefs degenerate and lose their function of protecting islands, coral reefs will shrink or even disappear under the damage of sea erosion and waves and typhoons, resulting in a reduction in territorial waters.
In the case of the Paracel Islands, for example, the degradation of the Paracel reefs has led to a decline in fish populations because coral reef fish use corals as their home, spawning grounds or shelters, which has a direct impact on the lives of the fishermen and islanders concerned.
Since the annual Coral Reef Ecological Survey conducted in 2010 in The Paracels, we have found that the prices of fishery products sold by local fishermen in the Paracels have been a rapid upward trend, which partly explains that the decline in catch has caused price increases. At the same time, in the exchange with the fishermen, it was also reported that the catch had dropped significantly compared with previous years.
An extreme example is the small octopus in Xisha. In 2010, the price of dried octopus in Xisha was 35 yuan / kg, and the price of small octopus fresh fish was 15 yuan / kg. However, the price of small octopus fresh fish rose to 30 yuan / catty the next year, while dried small octopus fish is rarely seen in the market, because the catch has declined, fresh fish has been in short supply, and there is no excess left to dry. In 2011, we rarely saw octopus for sale in Xisha. Although small octopuses can occasionally be seen when launching, the number is too small to sustain this market. In just 2 years, the little octopus "disappeared" from the market.
The reduction of fish catches not only affects the income of fishermen, but also affects the food composition of fishermen and people stationed on the island of Xisha, and once the support of land supply is lost, it is difficult to maintain the food demand on the island for a long time by relying only on the existing fishing catch on the coral reef.
Is there anything we should do? Is it just a matter of sitting back and watching the beautiful coral reef and the coral reef ecology it creates go from vitality to extinction?
In order to restore coral reefs, we "reforest" on the seabed.
Globally, more than half of coral reefs are already severely degraded, but the more serious problem is that the rate of coral reef degradation will accelerate in the future. If humans do not take any salvage measures, coral reef ecosystems could disappear from the earth by the end of this century at the current rate of degradation.
The existence of the coral reef system is related to the marine ecology and the lives of 500 million people, and we must not sit idly by and watch it disappear. From the Great Barrier Reef to the Paracel Islands, scientists from all over the world are banding together to solve this coral crisis.
Can we help reef recovery? Yes.
How can we help reef recovery? Protection + manual repair.
As coral reef ecosystems become more degraded, scientists and marine conservationists from around the world are also actively looking for ways and technologies to help coral reefs recover.
The current methods used are mainly divided into two categories, one is conservation, by removing the influencing factors that cause coral reef degradation, such as human destruction, pollution, overfishing, predators, etc., so that the resilience of coral reef ecosystems can self-restore; the other is artificial restoration, through artificial means to accelerate and assist the restoration of coral reef ecosystems, such as increasing coral populations through transplantation, cultivating corals, improving the bottom quality of coral reefs and so on.
In practice, the first type of approach is more important because no amount of artificial restoration of coral reefs can be restored without removing the threat.
However, for coral reefs with severe degradation, their self-recovery ability is weakened, and even if they are protected, they are difficult to recover, and they need to be restored in a combination of two methods.
| First, how do we protect coral reef ecology?
In terms of protection, the most important thing is to establish coral reef protection areas or national parks to strictly protect key areas.
Australia's Great Barrier Reef and Hawaii in the United States have established coral reef waters as national parks, and divided into different functional areas, strict protection of key areas, some areas open to recreational fisheries such as fishing. However, even so, under the influence of global changes, coral reef bleaching, long-spined starfish outbreaks, coral reef diseases, etc. still caused the degradation of many coral reefs.
China started late in this regard, especially in the planning of protected areas, the management of coral reef protection policies and regulations have not yet kept up. However, the "Regulations on the Protection of Coral Reefs and Bricks in Hainan Province" implemented in Hainan Province in 2017 has taken the protection of coral reefs a step further, strictly prohibiting the destruction of coral reefs and bricks, and more importantly, prohibiting the sale, purchase, transportation, carrying, and delivery of coral and brick products, and trying to curb the damage to coral reefs by the processing of corals and brick crafts from the source.
Conservation measures also include controlling the use of pesticides along coral reefs, reducing sewage discharge, and reducing the intensity of coral reef fishing.
Finally, there is another protective measure, the most important and the most difficult one to achieve, that is, to reduce carbon dioxide emissions, slow global warming, and reduce the scale and frequency of coral bleaching.
| How do we manually repair it?
In parallel with the protection, people have also begun to carry out artificial restoration of coral reefs.
Since the last century, people have tried coral transplantation and cultivation.
Japan, Israel, and the United States were the first countries to start research in this area. However, with the importance of Southeast Asian countries to coral reefs, from the end of the last century, Thailand, the Philippines, indonesia also began to try accordingly.
Corals need a sufficient number of corals for transplantation during the transplantation process, and severely degraded coral reefs often do not have much coral to supply, relying solely on the collection of corals from the natural environment in the wild may cause damage to the existing corals of the reef, so coral cultivation is needed to increase the number of corals. Therefore, artificial coral cultivation technology has also appeared.
Acropora tenuis transplanted from Japan grew into adults (a) and released large coral egg masses (b) in June 2015 (Credit: Zayasu and Shinzato 2016).
At present, the artificial coral breeding technology used by various countries is divided into two categories, using the characteristics of sexual and asexual reproduction of corals for breeding.
The former is the rearing of gametes or larvae produced by the sexual reproduction of corals, which develop into larvae or coral individuals and then be released or bottom-seeded for transplantation into coral reefs. The cultivation method using coral asexual propagation technology is somewhat similar to cuttings in agriculture, in which the broken branches of corals are cultivated into adult corals in artificial environments or under wild conditions, and then the adult bottom is transplanted back into the coral reef to increase the number of corals.
The advantages and disadvantages of the two category approaches can be found in the following table.
Comparison of the advantages and disadvantages of coral cultivation methods of the two species
Although there are many disadvantages to the use of sexual reproduction methods, its two advantages are indeed irreplaceable.
First of all, the genetic diversity of corals is very important for coral reefs and is an important basis for the resilience of coral reef ecosystems, and coral reef ecosystems with high genetic diversity can have better resistance in the face of different environmental pressures.
Secondly, once the problem of high mortality rate in the early stage of coral larvae is broken, a large number of coral larvae can be generated in batches to increase the rate of coral cultivation.
However, at this stage, the use of coral asexual reproduction methods is more practical and effective, and it is the main method adopted by the vast majority of countries.
In the field of coral cultivation, Japan was the first country to focus on the development of technology for cultivating coral larvae through coral sexual reproduction, and has applied this technology to the restoration of coral reef ecosystems and island protection.
Among them, the most concerned is that they transport the coral larvae and coral individuals they have bred to the Bird of Theos Reef to protect the reef from sea level rise and wave invasion and disappear. to maintain their claimed 160,000 square kilometres of exclusive economic zone (https://www.nytimes.com/2014/11/19/business/energy-environment/growing-coral-to-keep-a-sea-claim-above-water.html) based on Okinoki Reef.
In the past two years, Australia has also considered releasing artificially bred coral larvae onto coral reefs to increase coral populations in the hope of speeding up the recovery of coral reefs affected by bleaching.
Coral cultivation in tropical countries such as Palau, Thailand, Indonesia and other tropical countries is mostly the use of asexual propagation of broken branches, the use of iron frames or PVC pipe frames placed on the seabed as coral nurseries, on which corals are fixed to allow them to grow. Most of the areas they choose are waters with less typhoon impact, and the iron frame or PVC pipe frame used for coral cultivation is mostly placed directly on the seabed, without special fixation.
In the Caribbean, in addition to placing coral nurseries on the seabed, TNC (The Nature Conservancy) also uses ropes and floats to establish "coral trees" in the water to cultivate coral branches, so as to make more three-dimensional use of sea water bodies.
TNC's "Coral Tree" cultivation method in the Caribbean Sea (Image: https://curacaotodo.com/)
| We "afforestation" on the bottom of the Paracel Sea
Compared with foreign coral reefs and restoration work, everyone may be more concerned about our Coral Reefs and related restoration work in the South China Sea.
At present, the situation of coral reefs in the Paracels is not optimistic, the natural resilience of degraded coral reefs is insufficient, and the pressure of fishing has not been eliminated, so in the 10 years after the destruction of long-spined starfish, the recovery rate of coral reefs has been very slow, and some areas have even experienced some repeated phenomena of "degradation-restoration-degradation".
In order to restore the coral reef ecology of Xisha, since 2009, the Coral Ecology and Coral Reef Biology Discipline Group of the South China Sea Institute of Oceanography of the Chinese Academy of Sciences has started experiments on coral cultivation and coral transplantation technology in Xisha.
In the three years from 2010 to 2012, coral larvae were cultivated in The Paracels, where tens of thousands of coral larvae were obtained and released onto the reefs of the Paracels. However, due to the limited conditions of the Paracel Islands, the cultivation of artificial coral larvae on the island is difficult to expand.
Developing coral fertilized eggs (left) and attached coral larvae (right)
The water body in Xisha is smallly polluted, and the coral reef disk is vast, which is more suitable for wild cultivation, but the impact of typhoons is serious, and several typhoons directly affect the Xisha sea every year. If the method of Palau, Thailand and other regions is adopted, and the coral nursery is placed directly on the seabed without a solid and stable method, a single typhoon can cause all the results to be wasted.
Experiments on the Paracel Reef Disc showed that even if a 18 mm diameter steel bar was used to make a coral cultivation frame and nailed to the coral reef disc with a 30 cm long iron nail, it was still unable to withstand typhoons and waves. After the typhoon, half of the iron frame was pulled up by the waves and iron nails, and even some of the iron frames were directly scattered, and all the corals cultivated on it were lost.
Coral nursery made of iron frame (left) and iron frame destroyed after typhoon (right)
In order to reduce the role of typhoons and waves, we borrowed the method of TNC, using ropes, floats and PVC pipe frames to build "coral trees", using the elasticity of ropes and floats to reduce the force of waves directly acting on coral branches, effectively reducing the shedding rate of corals.
After more than 2 years of hard work, a small underwater "forest" composed of "coral trees" has now been formed in Qilian Island.
Although the "coral tree" has the above advantages, because it swings largely in typhoons, there are also collisions between the broken branches of the coral hanging from the fishing line, so many coral species with thin branches, fragile bones and sensitivity to strong water flow are not suitable for breeding on it, and corals with clumpy, shell-like and leafy shapes are difficult to bind with fishing line and are easy to loosen and fall.
In order to make up for this shortcoming, according to the seabed situation in Xisha, we have developed a floating bed type coral branching nursery for use in coral reef restoration as a supplement to the "coral tree".
Broken branches of corals growing on "coral nurseries" can grow 3-5 times in size in about 8 months.
The floating bed nursery is placed at a height of 1-2 m close to the seabed, less affected by the waves, and can cultivate corals of various shapes and fragile bones, but it requires 4 points of fixation, and the underwater work and time required to establish it are at least twice as much as the "coral tree".
When the corals on the nursery grow, each floating bed resembles an undersea flower bed, covered with corals of different shapes.
Corals growing on nurseries can provide habitat for coral reef organisms, especially during fish breeding, can provide shelter for juvenile and juvenile fish, and also provide feeding places for small carnivorous fish and squid, which also has an important role in promoting the recovery of coral reef fish populations.
From the "coral tree" that cultivates corals to the floating bed nursery, a large number of small fish can be seen living in it, and the nursery inadvertently plays the role of artificial reef.
However, the corals cultivated are only "temporarily" on the nursery, and the last step is needed to truly "take root", that is, transplantation to the coral reef.
After months of cultivation, the broken branches of corals need to be transplanted to the reef to be repaired to increase the number of corals in the area when they grow to the right size (10-20 cm).
Like cultivating corals, transplanting corals also requires protection against typhoons.
Because transplanted corals take months to grow their tissues and bones onto the reef, once there is movement during growth, the coral needs to re-build bones and tissues at its contact point with the reef's substrate. Therefore, once there are waves and typhoons, it is difficult for transplanted corals to grow firmly on the coral reef, and the mortality rate will rise significantly.
To avoid this, we secure the transplanted coral by tying it to the bones of the dead coral, fixing it with underwater glue, and tying it to a nail nailed to the seabed.
In the coral transplantation in Xisha, we have adopted a variety of transplantation methods, and achieved good results, the transplanted corals have grown firmly on the coral reef, and the individual has increased by 4-5 times, and it is possible that the first breeding corals may appear among them next year (now it can only be said that it is possible, it cannot be guaranteed).
Finally, as mentioned in the previous article, for each of us, although there may not be an opportunity to cultivate or transplant corals, if we start from the small things around us, it will also play a great role in the protection of coral reef ecology.
First, refuse to buy coral and brick crafts or souvenirs, because collecting corals and bricks can cause direct damage to coral reefs.
Second, when we swim, snorkel or dive in the waters near coral reefs, do not step on, pick up, or pick up coral bones.
At the same time, try to use physical sun protection in the sea, and do not apply sunscreen that is harmful to corals.
Secretly Amway's "face kini" of Qingdao's aunt (picture source see watermark)
Even if you don't go to the beach, you can still protect the coral.
In life, we can use less plastic products, which can reduce plastic pollution in the ocean, reduce the threat of coral from plastic waste and microplastics; reduce carbon emissions, and slow the pace of global sea warming.
Let us leave a glimmer of life for corals, but also leave a beautiful underwater garden for future generations, so that they can only taste this beauty from the images that remain.