We get many questions about our transplantation methods of corals on our artificial reefs. So let us explain what methods we use and why.
In the marine conservation world there are discussions going on about what the best ways are to regrow coral reefs. There are different methods and different conservation projects use them with various results. We aim to use the methods that have best long-term and sustainable results.
Coral reproduces itself in two ways:
- Sexual reproduction
- A-sexual reproduction
Both ways occur in nature or can be manipulated by humans.
Sexual reproduction is the natural process of spawning and coral larval settlement on (newly created) substrate. We humans can intervene with this and can collect during spawning the sperm and eggs and bring them to a laboratory. There coral larval can settle on an artificial substrate. After reaching a certain size the coral is transplanted (with the artificial substrate) to a nursery or straight on the reef in the ocean. Every sexual reproduced coral has new DNA.
If a larvae is settled to a substrate (in nature or in laboratory) it starts growing its first coral polyp. This polyp reproduces itself a-sexual, it clones itself and thus the polyp grows into a colony. One colony consists of many polyps which have the exact same DNA. It typically takes corals 25 to 75 years to reach sexual maturity. When it is sexual mature it releases gametes with sperm and eggs during spawning. The sperm and eggs from the same colony can’t fertilize to form a larvae, because they are from the same mother colony. They need to find egg or sperm from a different coral species.
There are two methods to use a-sexual reproduction as a method to regrow coral reefs.
1) The first method is fragmenting a mother coral colony. This involves breaking a healthy coral colony in many small fragments and connect these fragments on an (artificial) substrate. The fragments will grow on this substrate and start to reproduce themselves a-sexually, With this method you can convert one coral colony into hundreds or even more new colonies. This method generates new colonies in a quick way, because the colonies don’t start from one single polyp, but from a small colony. Most of the time branching coral types, which are fast growing, are clipped to smaller pieces. The downside from this method is, that the growth spurt declines after some time and returns to normal growth rates. More importantly this method creates mono culture. Every new colony has the same DNA as the mother colony, so they can’t reproduce themselves with these new colonies. Also they are vulnerable to the same diseases. This method is mainly used for growing corals for aquariums.
2) The second method is to go around a natural coral reef and look for broken-off pieces of coral. These pieces of corals are broken off by storms, marine life or human disturbance. The pieces (of a certain size) are collected only if they appear alive and healthy, without signs of disease, and if they are not yet overgrown by algal turf or sponges. These corals of hope are connected to the artificial reef and start reproducing themselves asexually. The result is only a few corals from the same colony are attached to form a new reef, one creates more biodiversity by collecting different species. Different growth forms of corals, like plate, foliose, encrusting or even brain coral, if you find one that is broken, can be placed on different locations on the artificial reef. The downside of this method is that it is more time consuming to find the coral pieces, instead of breaking one coral colony into many pieces. Also it takes more time for the slow growing species to form an abundant reef.
CoralGardening only uses the method of collecting broken-off pieces and connect them to artificial reef structures. When we find natural recruits on our structure we are extremely happy. If you want to now more in depth about these methods, just download this document.