All over the world, increasingly more coral reefs suffer from severe coral mortality. An estimated 40-50% has died over the last 30 years. One of our challenges therefore is restoring existing and creating new reefs. The work we do on the islands around Zanzibar is a start of a larger project. On the shores of mainland Tanzania dynamite fishing(*) is practiced a lot and poses a big threat to the reef systems. With our experience on the conservation work on the islands, we hope one day soon we can put our knowledge to practice in these areas that are in extra need of our support.
(*) Dynamite or blast fishing is the practice of using explosives to kill schools of fish. This illegal practice is extremely destructive to the surrounding ecosystem especially to the fragile coral that breaks in pieces. It kills indiscriminately, leaving the larger part of the dead and hurt animals on the oceanfloor.
How do we do this?
Corals are animals called ‘polyps’. A polyp lives in a symbiosis with algae (i.e. plants) called Zooxanthella. The algae live in the body of the polyp providing the polyp with food (see What are corals ). By using small fragments of a coral colony and planting these fragments somewhere else, we can give the colony a new living environment in which it can multiply and further grow. We have a special technique for this.
Coral farming and reforestation:
1st – over the years we have gathered mother corals that are the basis for the cutting of fragments, our ‘brood stock’.
2nd - after we cut a fragment, it is placed on a cement plug which is put on a bed on the sea floor. We have multiple beds, per coral species one bed; these are our ‘reef nurseries’.
3rd - after approximately 3-8 months the corals in the nurseries have grown sufficiently. During the entire nursing process our divers regularly clean these ‘coral childs’ and the beds, removing algae, sediment and predators like the Crown of Thorns.
4rd – in the meantime we select substrate to plant the coral plugs. We either plant the coral in existing reefs that have (partly) lost their corals, or we use different materials to plant the plugs on e.g. limestone, reef balls, etc. Limestone we get from the land. We drill holes in the stones to fit the coral plugs. Reef balls are from cement and made by us locally in a special mold (Courtesy of the Reef Ball Foundation). The balls have different diameters (we mostly use 80cm diameter), have different openings and are hollow inside (fish and other marine life hides in it). The reef ball has several ‘plug inserts’ on the outside to plant the coral plugs with the child corals. The advantage of the reef ball is that it does well on sandy areas where there is no basic substrate. This way we can make a new ‘artificial reef’.
5th - the coral childs are moved carefully to the area where we plan to reforestate. The plugs with the coral child are attached on the substrate with a special glue.
6th - we check the first weeks to see whether the plugs remain fixed on the substrate and clean them if necessary. After that it’s waiting for our new reef!
Some corals grow relatively fast, others slow. We try to make a natural reflection of the coral ecosystem in the area. The mix of planted corals is based on the example nature gives us.
Ongoing research on the reforestation is very important. We have a large network of NGO’s with whom we communicate on many different issues. The Reef Ball Organization is especially important for the coral reforestation project and has trained us to succeed in this project.