The Creation of Artificial Reefs
Written by BBC Science and Nature (Animals) - Take It Further on 18/06/07
If you mentioned the word ‘reef’ to most people they would instantly think of a picturesque tropical reef with schools of brightly coloured fish swimming through clear waters past sponges, sea fans and a multitude of different corals. Within the tropics this may well be the case, but outside these warm waters reefs still occur with schools of brightly coloured fish swimming through clear waters past sponges, sea fans and a multitude of different corals. Within the tropics this may well be the case, but outside these warm waters reefs still occur. Reefs in more temperate regions will only form in certain locations where a suitable hard substrate is available for invertebrates, including sponges and corals, to attach themselves. In many areas of the continental shelf, the bottom is covered with sand and there are no appropriate geological features to allow reef communities to form. Only 5-10 per cent of the bottom may be suitable for reefs to form, so man has decided to try and increase this figure.
What are they?
The oceans are full of microscopic plants and animals which rain down on to any exposed surfaces in a shower of life. Any hard surface can be colonised which is why boats cover their hulls with anti-fouling. By placing suitable long-lived, stable and environmentally safe materials on carefully selected ocean bottom sites, these structures can act much as a natural rocky outcrop would. Over a relatively short period of time every square centimetre of these man made structures becomes covered with encrusting marine life, which in turn supports other mobile reef-living forms such as fish. An artificial reef has been created. In theory these artificial reefs could be as productive as the real thing with the right background research before deployment. They can provide shelter, food and breeding sites for some species. The main limitations are from life-span. Even rocky outcrops eventually erode, so the longest these artificial structures can be expected to survive is between one and 500 years.
How do we make them?
Shipwrecks have always been popular with divers because they are great places to explore and see marine life concentrated in a relatively small area where it would not normally be present. It is no surprise that artificial reef programmes throughout the world have relied heavily on ships to create reefs. This practice has become more popular recently, especially in the United States and Australia. The economic benefits of creating a new diving site are not to be underestimated and ecologically they can produce huge new environments for marine life.
A series of ships is due to be sunk between 2001 and 2002 adding to a large number of ships which have already been scuttled: The USAFS Vandenberg is over 520ft long and weighs over 13,000 tons. It is nearly as tall as the statue of liberty. It has been meticulously cleaned and prepared and the project is strongly supported by the Florida Keys National Marine Sanctuary. The development of a reef on it will be carefully monitored and researched after the scuttling. The HMCS Cape Breton is due to be sunk off the coast of British Columbia on 20 October 2001. This is another massive ship which was used in World War II. It is hoped that by combining this site with the existing reef formed by the HMCS Saskatchewan off Shake Island, the waters surrounding the island will eventually be declared a marine park or marine protected areaThe HMAS Hobart will be scuttled in November/December 2001 off South Australia. The vessel is currently in Port Adelaide where it is being cleaned and prepared. Preparations include removal of all oil, fuel, sharp and protruding objects and doors and access hatches, widening of corridors, provision of large openings along the exterior of the ship, sealing of engine compartments and removal of all furniture and equipment not securely fixed. This should ensure that the artificial reef is safe for diving. It is estimated that after three years this artificial reef will generate an additional $10 million in business and create 127 jobs which will have a major impact on the coastal area.
Concrete
Concrete can contain toxic chemicals so there have been problems with using it in the past. Now that safe non-toxic forms are used, artificial reefs often incorporate concrete structures. These may be in the form of specially made structures (see reef balls), or recycled parts of old structures. Concrete is quite similar to rock in structure, so it is an ideal substrate.Reef balls.
The Reef Ball Foundation is an international non-profit group which has a mission to help restore the world’s ocean ecosystems. It has over 1,500 projects world wide. The reef balls in question are igloo shaped concrete structures which have now been patented by the foundation. The balls weigh up to 2,722kg (6,000lbs) and have dozens of holes through them to act as refuges for marine life. The concrete used has been specially formulated to promote coral growth. Reef balls are designed to mimic the rocks and crevices found in a natural reef system and have been used all over the world to repair damaged coral reefs or create new artificial ones. Reef balls are very versatile with many different shapes and sizes available. Some countries have actually seeded the balls with algae and live coral to give the new reef a head start.
Tyres
Tyres are notoriously hard to dispose of so it is not surprising that the huge tyre dumps which exist were one of the first substrates targeted for use in artificial reefs. They are an ideal shape for producing holes and gullies for fish to live in and the tread makes it easier for encrusting organisms to gain a foothold. Unfortunately many early reefs made with tyres were not sufficiently anchored. This substrate is still used today, but usually in combination with concrete.
Other materials
Since man intentionally started creating reefs all sorts of things have been used as substrate including cars, planes, tanks, buses and oil rigs. One of the latest additions are subway cars. New York City is retiring 1,300 subway cars known as Redbirds, most of which may be deployed to create artificial reefs off New Jersey and Long Island. How long have we been making them?We have been making artificial reefs unintentionally ever since the first boats were shipwrecked. Of course all of the early boats were wood and therefore very short-lived structures, so any reefs which may have become established no longer exist. Later metal-based ships still exist off many shores and many of these wrecks have established healthy reef communitiesThe practice of intentionally sinking structures to simulate these productive shipwreck sites did not take off in any organised form until the mid 1900s.
In the United States several states have artificial reef building programmes which go back more than 50 years. A good example is Alabama’s reef building programme which started in 1953 when 250 car bodies were placed off the coast. This proved to be very successful and in the following years more cars were added and later other reefs were created using culverts, bridge rubble, barges, tanks, boats and planes.Texas has followed very similar development with all manner of structures being used to create reefs over the last 50 years. The 1980s saw an unexpected boost to the states programme with a decline in oil and gas activity in the Gulf. This resulted in many rigs being scrapped and it was soon recognised that these huge structures would make invaluable additions to the reef programme. To date, around 50 rigs have been donated by oil and gas programmes and half the profit from not having to scrap the rigs has also been donated into the project, making it self sufficient. Today, reef programmes are very advanced ventures spurred on by the fact that fish stocks are dwindling and natural reefs are threatened by habitat destruction.
All over the world, countries are starting to realise the potential of artificial reefs and in Hong Kong one of the most ambitious programmes is underway. Since 1996 they have been implementing a $100 million plan to enhance fisheries and promote diversity in Hong Kong’ marine environment.This development has included the deployment of 20 ships, 216 tyre units, 131 concrete modules (including reef balls) and eight quarry rock units. These were placed in existing marine parks, but the next phase of the project will concentrate on five new areas outside existing marine parks. In the short period since the initial phase of this development researchers have observed very impressive populations of highly valued reef fish. Over 110 species of fish have already been recorded on these artificial reefs.Are they a good idea?It does seem that the world is getting better at creating artificial reefs and the days of haphazard dumping of just about anything are definitely numbered. In the US, only concrete and heavy gauge steel is allowed to be used for reef construction and any ships used must be thoroughly cleaned and meticulously prepared. Most scientists agree that artificial reefs cannot reverse damage that has been caused by man to natural reefs, but others would argue that several reefs have been successfully repaired and some valuable new reefs have been created. It cannot be disputed that one of the most important outcomes of the artificial reefs to date, has been to relieve pressure on natural reefs which were being overfished or constantly disturbed by divers and tourists. By creating other distractions where marine life can be observed, people can be drawn away from high risk areas. In this function, artificial reefs have definitely been a successIn the future, research and technological developments may help us to create new reefs with the diversity of habitats required to support full scale communities. Some countries appear to be getting close to this goal, but most of the artificial reefs created so far are more like oases in a desert. These new islands of life may well attract fish from surrounding areas, but because they are so well charted they often become targets for anglers. Because of this, they may be acting more as a trap, causing fish to concentrate in areas where they are more likely to be caught, when normally they would be more dispersed and harder to catch. Much more research is needed to decide whether artificial reefs do have an impact on fish stocks, and in the meantime, stricter controls on fishing new reefs may be a wise precaution.
And finally...In the US, one company has come up with an ingenious way of getting the public involved with artificial reef creation. Eternal Reef, Inc has introduced Memorial Reefs as a proactive way to encourage growth of the marine ecosystem. By blending a persons ashes into a specially designed reef unit using the reef ball design, that person’s life is uniquely remembered whilst creating a foundation for new life. Eternal reefs will also place the ashes of more than one family member including pets within the same Memorial Reef unit!
Editorial Comment: It feels good to report some encouraging news !! However, we still need the shark to protect these 'artificial' reefs !! |
