It should come as no surprise that coral reefs are in peril. Healthy reefs are disappearing from the planet at an alarming rate. A surprisingly large percentage of food, medicines, coastal protection, and tourism income that the world depends on come directly from these reefs and will disappear equally fast as the reefs themselves. Because these habitats are so vital to continued prosperity, marine researchers have been left scrambling for a way to rehabilitate sick and dying reefs of the world.
People started to notice that undersea shipwrecks held a higher amount of marine life than nearby areas. Corals would adhere to the hard skeleton of the ship, fish would hide in the cabins and open spaces, barnacles would encrust the exterior, octopus and other invertebrates could be found in the cracks and crevices the sunken ship had created. So, an idea immerged; what if we could create our own artificial reef structures? Could those replace natural, centuries old reefs? The answer was quickly a resounding “No, of course not”. There is no substitute for proper coastal management. But, artificial reefs can help play a role in aiding the health and recovery of natural reefs.
The earliest days of artificial reefs were mostly quite a bit of trial and error. Anything from old trash (shopping carts, metal barrels, pots, etc) to piles of old tires, to fully intact cars and boats were optimistically thrown in the ocean.
While this did sometimes provide homes to invertebrates and hiding spots to small fish, they were generally not long-term success stories. Cars, domestic appliances and other “junk” disintegrates in about a decade and certain paints, enamels, and other coverings can be harmful to ocean organisms. Corals have a hard time colonizing plastics, rubber, and some metals, and some of the artificial reefs have broken free, smashing natural reefs.
Though we are very much still in that trial-and-error phase of artificial reefs, there has been an emerging standard in man-made structures. Concrete domes with symmetrical holes called Reef Balls (pictured below) are the most recognizable artificial reef structure along marine coasts. They can be small (half a meter in diameter), to large (several meters in diameter), formed to include layers for lobster homes, or specially formed to use as coral nurseries or oyster beds. The concrete should form a hard surface for the coral to adhere to, and they are heavy enough to remain stationary even in storms and strong wave action. The concrete doesn’t contain harmful chemicals that will leach out into the water and each structure is expected to last for hundreds of years. The holes allow for sunlight to penetrate most spaces and for proper circulation to occur. There have been varied results across the globe, but in some waters, these reef balls have been astoundingly successful, supporting a biomass of fish that is even greater than similarly sized natural reefs.
However, rehabilitation alone is not going to save the oceans. Rehabilitating a habitat is always much more expensive than preventing destruction from happening to begin with. Reef restoration is complicated, tricky, and has a very low success rate, and corals are notoriously among the most difficult habitat to restore once it is decimated.
Reefs with a high degree of human influence (i.e. fishing, salinity changes, pollution, etc.) are categorically less resilient and less likely to recover from disturbances such as bleaching events, tsunamis, or other storms. With proper management and protection, these reefs can become more resilient and more likely to recover without the need for human intervention. Therefore, without proper coastal management in place, there is no point in active restoration attempts. It cannot change much as an isolated program; reef rehabilitation must be part of a broader management scheme to predominately protect the natural reefs. With proper protection measures in place, the rehabilitation and restoration attempts will have a much greater chance of aiding a failing reef and bringing the biodiversity back to levels we depend upon.
There are plenty of reef restoration attempts occurring throughout the world. Many of these are found at high end dive resorts or through very simple NGOs and everything in between. Diving on these artificial reefs is becoming somewhat of a tourism attraction and many places will let you help out or sponsor your own reef structure. If this is of interest to you, plan your next dive holiday to include some conservation with your bubbles.
‘Intro to Reef Restoration’ was written by Marine Biologist Roya