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Coral reefs support a quarter of all marine life and offer natural coastal protection against powerful waves. They also provide jobs and income to millions of people.
However, corals currently face multiple stresses, such as increases in temperature, ocean acidification, and overfishing. All of them create damaging changes to the ecosystem that could put coral reefs at risk of disappearing entirely.
To counter that, many groups are exploring innovative techniques for the restoration of coral. Active coral restoration refers to planting and raising corals in nurseries that rejuvenate depleted reefs and enhance coral cover in areas affected by warming ocean temperatures, hurricanes, disease, and other sources of coral loss.
Despite their plant-like appearance, corals are actually colonial animals that share ancestry with jellyfish and anemones. Some corals exist as single anemone-like structures. Meanwhile, many are colonial structures or clones constructed of thousands of individual coral polyps.
Each polyp has a circular mouth surrounded by tentacles that can strain small floating plants and animals, referred to as plankton, from the water. Hundreds of such polyps can combine to function as a single animal.
Inside the tissues of many coral species, particularly those that make reefs, are symbiotic microalgae. Called zooxanthellae, they can photosynthesize during the day, capturing sunlight and carbon dioxide to make sugar for the coral.
This sort of relationship is called symbiotic mutualism, where both the coral and the algae live together and mutually benefit. The algae provide extra food that they share with the coral in sugars. Meanwhile, the coral provides both safe housing and extra nutrients.
Many coral colonies are sessile, which means that they are fixed in one spot. Meanwhile, some soft corals are capable of moving about (much to the alarm of some first-time aquarium owners!).
One of the most remarkable adaptations that hard corals have is the ability to draw calcium carbonate from the water and form hard structures for the soft polyps to grow on. This incredible process forms coral reefs. It is also an important way in which the ocean can help trap carbon dioxide from the atmosphere.
Corals come in a staggering array of sizes, shapes, colors, and textures. They form the foundation of many shallow, clear, warm-water, tropical marine ecosystems. However, some species of coral exist even in frigid polar waters, in the gloomy plumes of sediment that flow from the Amazon river, and in the total darkness of the deep sea.
Corals make up a good chunk of the diversity of the Cnidaria phylum. It also includes jellyfish, anemones, and many bizarre gelatinous creatures you maybe haven’t heard of, like siphonophores.
Within this group, corals make up the Anthozoa class that can be further subdivided as follows:
Up close, the polyps of this subclass have six tentacles. These corals are the ones that create a hard foundation of calcium carbonate on which the fleshy polyps grow. The continuing cycle of thousands of corals slowly building their skeletons, dying, and new ones settling builds the massive reefs that protect small islands and provide food and homes for countless marine creatures.
This subclass comprises some of the most famous coral species around the world, often referred to broadly as hard and stony corals. Examples include the iconic Staghorn and Elkhorn coral that are now threatened species but once made the main building blocks for Caribbean and Floridian reefs.
As the name suggests, corals in this subclass have eight tentacles that grow symmetrically away from each other. More practically, this group includes soft corals, such as the previously mentioned ones that can move around, gorgonian sea fans, and sea pens.
Unlike the so-called stony corals, the corals of this subclass do not build reefs of calcium carbonate. They do, however, grow on them. They also rely on their tentacles to filter feed rather than having algae to photosynthesize. This means that they can thrive in total darkness in some places and often grow in areas with high flow-through of water.
In much of the Caribbean and the reefs around Florida, sea fans are prominently waving in the currents with the motion of the waves. Interestingly, most sea fans in the Indo-Pacific are stiff and cannot flex far without breaking. They do not have a hard exoskeleton and, instead, have small sclerites that give them individual structure.
There are many different species of corals. Some are boulder-like structures, whereas others form incredibly intricate branching patterns like plates or petals of a flower. These are foundational species on which many organisms depend and collectively form reefs big enough to be seen from space.
Corals can reproduce both sexually and asexually. Asexual reproduction involves budding or fragmentation. When budding occurs, new polyps bud from their parent polyps to form new colonies.
Meanwhile, fragmentation occurs when a piece of the colony breaks off to form a new one, often from the concussive force of waves during storms, disturbance by large marine animals, or hapless humans! Most fragments that are broken off and rolling loose on the reef do not survive the trauma unless they happen to get wedged into a protected spot where they can continue to grow.
In addition to that, corals can reproduce sexually, using sperm and eggs. Some species produce eggs and sperm simultaneously, while in other species, colonies may produce either eggs or sperm.
As most corals can’t move in order to maintain a sex life, so to speak, corals engage in broadcast spawning. Male and female corals release their reproductive cells. When the egg and sperm successfully meet, they will form baby corals.
These baby corals, called planulae, float until they find a hard surface they can attach to and continue growing. What governs where larval coral will settle and successfully grow is a complex question that many scientists have spent decades studying to better understand how reefs recover or die after disturbance.
Spawning is a mass event that occurs annually on most reefs. Many species somehow coordinate with queues from the moon, the water, and perhaps chemical signals from each other to release their reproductive material all in one night. This can help them to overwhelm predators and maximizes chances of successful fertilization. It is a mysterious and awe-inspiring natural phenomenon to observe!
In the last 30 years, over 50% of the world’s coral cover has been lost. Many Caribbean reefs have lost as much as 80% or more of their coral cover. What were once colorful aquatic cities bustling with fish and invertebrates are now turning into barren, degraded ocean cemeteries. But why?
Years ago, people would ask, “If the climate is changing, why aren’t we seeing any signs?”
Today, sadly, the signs could hardly be more shocking. Dramatically-changing weather patterns and increasingly severe storms cause potentially irreversible effects on the diversity of life on our planet.
When sea surface temperatures increase, the various stresses that corals experience, such as nutrient pollution, runoff from urban and cleared landscapes, overgrowth with algae caused by the loss of herbivorous fish, invasive species, and more, all work together and can push corals over the edge. A stressed coral can’t just call up a therapist for a chat.
When the water temperature gets too hot for too long, reef-building corals seem to panic and kick out the symbiotic algae that turn sunlight into sugars in a phenomenon called bleaching. In a single day, a mass bleaching event can turn a vibrantly colored coral reef into a bleached white ghostly graveyard.
If temperatures fall or a reef is otherwise healthy, many of the corals can pick up new algae and survive. Far too often, though, our fragile, slow-growing corals are simply too stressed, and huge numbers bleach and die.
Today, a third of all emissions have been absorbed by the oceans. As a result, global ocean temperatures enhancing by 0.14 degrees Fahrenheit or 0.08 degrees Celsius every decade since 1971. Keep in mind this is an average number across the entire ocean. Individual reefs will experience far greater increases locally when extreme conditions of weather, currents, and tides combine.
Even a sustained shift as low as 2.7-3.6 degrees Fahrenheit or 1.5-2 degrees Celcius held for a period of weeks can produce coral bleaching. Moreover, the increased carbon dioxide absorbed by the ocean is causing it to acidify. This makes it harder for coral to form calcium carbonate and slows the overall growth rate of coral reefs everywhere.
When coral reefs are severely degraded or disappear, the animals that depend on them do as well. Along with that, the ecosystem benefits they provide for humanity, like coastal protection, fisheries, and tourism, decline often with major economic consequences.
In 2016, temperatures reached a record-breaking high, causing mass bleaching on a global scale. This one event altered 93% of reefs in the Great Barrier Reef, one of the biggest and most diverse ecosystems on the planet.
By 2050, reefs are predicted to erode and deplete faster than they can restore themselves, causing net reef ecosystem dissolution and increased coral disease. Although corals have previously been exposed to different climatic conditions, the current rate of climate change seems to be unprecedented. Without significant intervention, our coral reefs around the globe may disappear entirely or shrink to the sad shadows of what they once were.
People are exploring coral reef restoration efforts to improve coral reef resilience in various places worldwide, especially in areas where coral recruitment is limited.
Consequently, people now perform coral gardening and have become coral farmers and new reef managers. Some culture coral larvae. Others propagate coral colonies through fragmentation and then attach small healthy corals to underwater structures. This process catalyzes re-growth in damaged areas.
By selecting corals that are seemingly more resilient to high temperatures and diseases, then raising them in coral nurseries, scientists may be able to cultivate stocks of coral that can be planted back out on the reef. This can help replenish corals in areas where reefs have been damaged or disappeared. It may also help reefs withstand warming temperatures, giving them a fighting chance.
Divers transplant young coral fragments from a coral nursery to old reefs using either cement, epoxy putty, or even zip ties depending on the approach to fix them to the surface of natural or artificial reefs in the hopes of stimulating reef regrowth.
Another problem surrounds the fact that coral and marine algae, aka seaweeds, are locked in a constant battle for reef domination. Coral relies on healthy populations of herbivorous fish to be their allies in fighting back against algae that can overgrow and smother them and even wage chemical warfare that can itself cause bleaching.
Many of these algae are native to reefs, while some are introduced. On countless reefs around the world, the loss of herbivorous fish from overfishing and run-off from areas humans have cleared of native vegetation are tilting the battle in the favor of invasive species.
Coral gardening can also involve the removal of algae in cases where the herbivorous fish cannot keep up.
In order to restore coral reefs and improve ecosystem services, conservationists are using a variety of reef restoration techniques. They are also creating innovative technologies to record coral depletion, plant coral fragments, search for genetically resilient coral populations, and protect reefs globally.
Active restoration may help keep coral reefs alive and sustain the livelihoods of local communities around them while the world works on global and local policy efforts to curb the most damaging effects of climate change, pollution, runoff from degraded land, and overfishing.
Most corals grow extremely slowly, sometimes only centimeters in a year. This is why being careful while enjoying coral environments is so important. While diving or snorkeling, do not get too close to the corals in case your gear knocks them. In addition, refrain from touching them.
If you are not an experienced diver and do not have good buoyancy control, sign up for a PADI Peak Performance Buoyancy course prior to swimming in and around reefs. Not only can you undo decades of growth to a given coral with a careless fin kick or bump with a tank, but you can also injure yourself!
It is not solely pollutants in the atmosphere and coming from the land that are causing harm to corals. The pollutants visitors release into the water without realizing it during their visits to reefs can be harmful, too.
Ingredients in sunscreens, such as oxybenzone, octocrylene, and octinoxate, can cause significant toxic damage to marine and tropical reef ecosystems. These chemicals leach into coral tissues, enhance bleaching, alter DNA sequences, and meddle with sexual coral reproduction.
Always look for “reef-safe” or “coral-safe” sunscreen. In general, though, it’s a better idea to simply cover up with “stinger suits” or “rash guards.” These thin material coverings have the added advantage that you will use less sunscreen. They cause less pollution and also provide protection against small stinging organisms sometimes encountered in the water.
“Leave only footprints (or, in this case, bubbles)” or “Leave the place better than you found it” are both phrases you’ve probably heard before. Yet, people still struggle to implement them fully.
Of course, we all want to see and experience coral reef systems to better understand and appreciate them. Part of that is being mindful to look but not touch coral. However, it’s also on you as a visitor to make sure you do not contribute to the massive problem that is litter and human rubbish in the ocean.
Be sure whether entering from the beach or the boat to minimize and be mindful of rubbish that might get blown by a breeze into the sea. In addition, check your pockets before jumping in.
Even better, if you want some good coral reef karma and are a more experienced diver, consider designating a zip pocket where you and your buddy can collect trash you find on reefs to dispose of properly.
That said, be careful as coral is very fragile. It’s not hard to do more damage than good, for instance, removing a fishing line from a branching coral. If in doubt, point it out to an experienced diver or trained dive professional. They will decide how best to proceed.
It’s also a good idea to see if you can join a beach clean-up day. You can also contribute to a local organization that takes care of removing litter from the beaches or reefs.
When overfishing in reefs occurs, the coral reef ecosystems quickly collapse. In healthy coral reefs, fish such as parrot fish and surgeon fish eat seaweed and maintain non-harmful algal growth rates.
When overfishing occurs, reefs can get out of balance, and algae can completely overwhelm corals causing bleaching and death. When there is no more coral, even species that fishing doesn’t target will begin to decline. A healthy coral reef is crucial to fisheries, and local economies. Over 25% of sea life depends upon coral reefs for survival.
Ship groundings, trawling, and blast fishing also dangerously affect the active restoration and ecosystem services coral reefs provide for their surrounding environment. Avoid restaurants that offer live reef fish you can pick to eat. Many of these rely on damaging practices like cyanide fishing. They stun fish and collect them, causing damage to corals and reef fish communities.
Choose to buy sustainably caught fish, advised by organizations like the Monterey Bay Aquarium Seafood Watch. You can help maintain a healthy ocean that can provide for human populations today and protect reef systems for future generations.
Ultimately, your habits and choices as a consumer can enhance the health of the ocean and govern significant improvements in the seafood industry and its sustainability. People choosing to pay a bit more for a sustainable seafood option, asking about where the fish comes from, and refusing unsustainable or unknown options play an important role in shifting the direction of seafood sustainability
Reduce, reuse, recycle, and don’t leave your trash on the beach or in the ocean. In fact, don’t simply avoid buying single-use plastic but invest in a reusable bottle and equipment that will not pollute coral reefs or affect their active and passive restoration.
Fertilizers applied to gardens and agriculture near reefs will often leach into local waterways. From there, they flow into the sea, causing harmful algal blooms and damaging corals. Generally, using less fertilizer in sensitive areas can go a long way to keeping reefs healthy.
Ecologically friendly gardening techniques like organic fertilizers, natural pest controls, compost, and mulch, can allow gardens and reefs to co-exist. Paying attention to the gardening practices in the places you choose to stay. When appropriate, encourage or reward financially (think tips!) places that garden responsibly can make an important difference, incentivizing better practices.
Managing nutrient pollution can reduce coral bleaching. Therefore, it can make coral colonies more resilient to temperature increases and enhance coral reproduction, coral growth, and reef restoration.
In many tropical reef destinations, you can also find opportunities to visit biodiversity-friendly farms that use sustainable agricultural practices to produce delicious foods that are also good for the environment.
Agro-forestry systems like those that produce shade-grown chocolate or coffee can help recover deforested land and reduce runoff to reefs. It’s worth keeping an eye out for these products. In addition, look into opportunities to visit farms like this to support their environmentally friendly approaches.
Reefs can be quite sensitive to fishing pressures. Both physical damage by anchors or trawling, as well as the biological effects of losing important reef fish, affect coral reefs. Reef managers keep an eye on active fishing gear used around coral gardens or by fishing trawlers that scrape along the sea bed and destroy corals.
If you are planning on fishing in tropical ecosystems, ensure that you and/or your operator are respecting local laws of marine protected areas as well as local customs. If you find yourself on a boat that is damaging reefs with its anchors, have respectful conversations with the operator about alternative methods like established fixed moorings to which the boat can attach.
A healthy reef can provide an abundance of fish for people to enjoy, whether as observers or fishing. Unfortunately, many reefs are too vulnerable to fishing pressure in their current state of stress.
There are volunteer programs all over the world that allow you to see firsthand the physical impacts of climate change on reefs and understand coral reef restoration techniques. Coral Restoration Foundation in Florida is one of the largest organizations providing such opportunities. You can learn more about how you can join and help here.
A high abundance of volunteers has worked in recent decades with community managers in marine protected areas. They learn how to scuba dive as well as take part in coral restoration and planting of new corals.
If you are unable to volunteer or just want to amplify your impact, donating can also be an important way to help.
When it comes to ecological engineering and coral restoration, there is a lot to learn about. At the heart of sustainability is education, and spreading the word about the significant impacts climate change is continuing to have on damaged reefs, and coral reef conservation efforts are key.
Our ability to grow corals and the small-scale restoration success conservationists are having in various places around the globe can help inspire people to act, volunteer, and educate others about the importance of coral reef restoration.
The ocean also needs outspoken advocates to advocate for both local and global changes in policy to curb greenhouse gas emotions, reduce pollution, and improve the health of fisheries.
There are various resources available online, such as interactive webinars by the Reef Resilience Network. It’s an online community for marine conservation managers to connect with experts and resources on coral restoration.
The tourism sector has huge opportunities to change the way the general public interacts with natural environments and enhance coral reef restoration at the same time.
Where available, choose tour operators that have eco certifications and can prove how they are giving back and adding to the preservation of particular ecosystems that face global extinction.
In remote locations where such programs do not exist, engage your operator in conversation about issues surrounding sustainability and conservation. Make clear this issue is important to your choices as a visitor.
At the heart of all our tours and work is sustainability. We believe that wherever you go, you should leave it in the same or a better state than you found it. That’s why we promote tours that will give back to particular ecosystems and environments, connect with the local community, and educate our guests on how to be better stewards for the planet and save coral reefs.
Would you like to help support our planet? WildVoice allows you to easily pick and sign up for wildlife and nature conservation volunteering events across Hawaii, South Florida, and California. If you’d like to explore these regions sustainably, check out our wildlife tours.