Artificial reefs serve as a possible remedy for natural coral reefs that have been damaged either by pollution, temperature (in the form of coral bleaching), or too much manhandling from snorkelers and divers, just to name a few. They can provide new habitats which can increase the populations of fish, from local reef fish to larger pelagics, and they can take some of the pressure off of a reef enhancing the reef's ability to rejuvenate.
Scientists, conservation organizations, and groups invested in tourism are looking for new methods and materials for establishing artificial reefs. Two of the most common artificial reef formations are sunken wrecks and concrete structures, sometimes referred to as "reef balls." Wrecks have been around since man has sailed the seas and there are many which serve as unwitting artificial reefs. But today, we find organizations that take decommissioned vessels, clean them of any potential pollutants and deliberately sink them. These wrecks could last from 50 to 100 years or more and in that time, a substantial reef structure can form - one that could possibly outlive its original foundation.
Reef balls, basically made of concrete and other ground up substrate that can provide a firm base for coral growth, are perhaps less mysterious than sunken wrecks and a bit more plain-looking. However, they can provide a very natural-like foundation for a coral reef and, given time, they can look for all to see, including man and animal, like any other natural reef given enough time for coral and sea grasses to take hold.
There have been other candidates for artificial reefs. Along the California and Gulf coasts, retired oil rigs are being debated as potential artificial reefs when the upper superstructure is removed to just far enough below the surface so as not to pose a shipping hazard. Other structures have become artificial reefs sometimes by accident. In San Diego, California, the NOSC (National Oceans System Center) closed down a research tower situated about a mile offshore, in the late 80s, and was preparing to turn it over to the Scripps Institution of Oceanography. Unfortunately, before Scripps could take possession, heavy storms came in and knocked it over: a loss to Scripps but a gain for local mussels, anemones and a wide variety of local fish - not to mention local scuba divers who now had a new underwater attraction to break up the wide, sandy vista of San Diego's Mission Bay.
But not all artificial reefs have been successful, regardless of the best of intentions and considerable thought put into the design. Not everything that mankind makes can become a suitable foundation for a reef. Case in point, the disastrous Osborne Reef off the coast of Ft. Lauderdale, Florida.
In the early 70s, Broward Artificial Reefs, Inc. proposed an extensive artificial reef consisting of discarded tires. The supposed benefits would be the elimination of unsightly, old worn tires and the chance to entice more game fish for recreational fishing. The project was endorsed by the U.S. Army Corps of Engineers and, with the aid of many private, commercial and even naval vessels, the Broward County government deposited over two million tires, bound together with steel clips, cables, or nylon rope, across 36 acres. A new artificial reef seemed to be on its way.
But it was not to be. The securing cables, clips and ropes corroded and the lightweight tires were now on the move. Pushed around by currents and storms, the tires smashed into living corals as they spread out like an ever-increasing steamroller. After one particular storm, thousands of tires piled up against a reef, while others made their way to local beaches.
Even if the tires had managed to stay together, it turns out that they were not a good platform for reef growth due to their flexibility and the fact that, as the rubber breaks down from long exposure to sunlight and seawater, several low-level toxins are given off which have the potential to stunt the growth of sealife.
"The really good idea was to provide habitat for marine critters so we could double or triple marine life in the area. It just didn't work that way," said Ray McAllister, a professor of ocean engineering at Florida Atlantic University who was instrumental in organizing the project. "I look back now and see it was a bad idea."
Reef Rescue videotaped the condition of the tire reef in 2010:
From time to time efforts have been made to salvage the tires. State campaigns have been put in play, often supported by the military (Navy divers have used the cleanup as part of their training), but the cost is enormous and so progress has been in fits and starts. The military has scaled back their involvement as their resources are being taxed by two wars and looming budget cuts. To date, around 73,000 tires have been recovered - a considerable number, but with the original number totaling over 2 million, there is a long ways to go.
"We've literally dumped millions of tires in our oceans," said Jack Sobel, director of strategic conservation and a marine scientist for the Ocean Conservancy scientist, when speaking about the concept of tire reefs on a worldwide scale. "I believe that people who were behind the artificial tire reef promotions actually were well-intentioned and thought they were doing the right thing. In hindsight, we now realize that we made a mistake."
We are now getting to a point with the condition of the oceans and marine ecosystems where there is less tolerance for "experiments" and a greater need for solutions for which we are much more certain about the outcome. Unfortunately, our actions that adversely impact the marine environments are bad enough; we can't afford to have our solutions simply add to the problem.
Read more about the history of Osborne Reef.
Read more about the reef in 2007 in USA Today.
Read more about cleanup efforts in 2010 in Reef Rescue.