Updated: Nov 14, 2021
The Great Barrier Reef and many other reefs like it are in dire straits. Rising temperatures make it difficult for corals to reproduce naturally during their spawning events. Corals are animals, and once a year there is a massive spawning event when they release eggs and sperm into the water to mix and be carried throughout the reef by currents. The harvesting of wild corals is detrimental to reefs, even if global warming was not already affecting coral reefs. However, the aquarium trade may be able to address both of these issues, and aquarists can do their part to help save the reefs.
First, what is coral fragging? Back in the day, and still too often today, the corals sold in aquarium stores are "fragged" or cut up and fragmented from living corals in the wild. Sometimes this will kill the coral, sometimes it won't, But the heavy traffic of divers, harvesters, and collectors is detrimental in itself. What you think of as a coral, is in most cases actually a multitude of individual organisms (polyps) living in a shared skeleton. This skeleton can be broken off and the colony fragmented into smaller colonies. This form of propagation, when done properly, shouldn't harm or kill the polyps or the colony.
The home aquarist can acquire the tools and the knowledge necessary to grow their corals to a healthy size and safely propagate them by fragging. These fragments or "frags" can then be easily sold or traded to other aquarists. With the use of artificial selection, new and never before seen colors, morphs, and varieties of corals can be shared throughout the hobby. This method of coral propagation is much better for the environment, as it reduces harm to wild corals and eliminates the need for traffic in the reefs.
As for the problem of rising temperatures, I mentioned aquarists artificially selecting corals for beauty, what about selecting for heat-tolerance? This is what the scientists at the Reef Restoration and Adaptation Program are working on now (Crow 2021). Corals in the northern Great Barrier Reef are naturally more tolerant of heat as the water is warmer. These corals can mix genetically with cooler water southern varieties and create more heat tolerant offspring. Scientists are trying to speed up the adaptation of heat-tolerance by breeding species of coral with up to 26 times more heat-tolerance and introducing them into less tolerant wild populations (Crow 2021). This is done by selecting for heat-tolerance in the polyp tissue as well as in the symbiotic algae that lives within the polyps (Crow 2021).
There is some risk however. Artificially selected hybrid species introduced into nature may become invasive, as their effect on the environment and how they will compete with natural species can never be perfectly predicted (van Oppen et. al. 2015).
If you want to start propagating your own corals at home, you'll need some basic tools. Firstly, a good pair of bone cutters. These powerful shears will cleanly cut through the coral skeleton without too much chipping. Next, you'll need frag plugs. These plastic or ceramic plugs are what you will glue the newly cut frags onto. That brings us to coral glue or epoxy for attaching to the coral to the plug. Finally, a good coral dip is necessary to promote tissue regrowth, fight off infection, and kill parasites. Don't forget a pair of forceps, a net or strainer, and a couple five gallon buckets as well.
van Oppen, et. al. Proceedings of the National Academy of Sciences of the United States. 112 (8) 2307-2313. 2015.
Crow, J.M. Nature 595, 142. 2021.