Today, 65% of coral reefs are dying all over the world. They die for many reasons: natural disasters such as the 2004 tsunami and bleaching caused by rising water temperatures. Anthropological pressures from burgeoning coastal communities and tourism cause sewage flows and pollution, leading to algae growth, coral smothering and disease. A reef system that took hundreds of years to grow can be destroyed in a single day by physical damage caused by dredging, anchoring, dynamite or cyanide fishing, or simply from indifference or negligence. When reefs die fish populations disappear, beaches wash away and land erodes from waves, fishermen lose their livelihoods, tourists find somewhere else to go, dive operators close and divemasters become jobless.
It doesn't look good does it? But what can we do? The universal answer expressed is that of protection. Prevent blast fishing, reef anchoring and pollution, while encouraging more sustainable fishing practices, will allow coral to be spared further damage and to repair itself through natural growth. Reef conservation is the most cost effective measure we can take and, for that reason, should always be practiced wherever and whenever possible.
Others believe the preventative approach is like King Canute attempts to turn back the impending waves. A more active solution is to take matters into our own hands and build coral reefs ourselves. Successful artificial coral reef programmes have been initiated in Bali, Komodo, Malaysia, Maldives and many other destinations worldwide. But where to start, what to consider and how do you do it? Don't worry, everything is in hand, here's our practical ...
By Sheldon Hey
Before starting on your artificial reef project, it's important you recognise that there are several issues of national importance regarding man made reef activities. These include permit programmes, regulatory requirements, reef construction materials criteria, liability, research and evaluation, site location, and the role of all parties involved in artificial reef development, management and regulation. It's no longer a case of dumping a few old tyres into the sea and watching to see what develops. That said, following a few basic steps will see you on your way to a successful project that addresses all the salient issues.
Just because you opted out of the rat race and became a dive-bum, doesn't mean to say you don't need to follow best practices anymore. Planning is probably the most crucial aspect of making an artificial reef. Every hour spent now can save days of work later, fixing problems that you should have thought about earlier. Your success will ultimately reflect the quality of prior planning and ongoing management that you put in.
Your starting point will be to determine the purpose of your project - there are many reasons to start an artificial reef such as creating a new dive spot, repairing existing damaged reefs, rescuing imperilled corals from other sites, or protecting endangered and indigenous species. This purpose will shape the decisions and actions you must take during the rest of the project. No artificial reef project can be successfully designed without knowing your specific reef objectives, to guide the design and construction of the reef, to reef placement, sizes and numbers of reef units to use, and special features your reef made need.
Next, determine your budget - artificial reef projects can vary from a few hundred dollars to hundreds of thousands of dollars and what you can fund will determine what options you have.
Other specific factors to consider include aspects of socio-economics, performance evaluation and monitoring. You may need to perform an environmental impact assessment and always you will need to bear in mind cost effectiveness and the expected benefits of your project.
After some very necessary planning time, you're going to need to set up a project team and split up the roles and responsibilities required for the job. Many successful projects do a large amount of monitoring and data collection, and require a reef monitoring programme for a minimum of 3 years. There are lots of tasks that need performing in these projects: project management, public relations, sourcing materials and labour, doing fish counts and bottom surveys, water quality analysis and monitoring, photo documentation of coral growth rates, scientific studies, and security enforcement, etc.
It will also be useful at this point to consider such issues as ownership, reef usage, liability and regulation of the reef. Often these issues are forgotten, but they are critical to success. For example, most coastal waters are common grounds that can not be legally owned, so how will you enforce a no-take zone? If your coral reef impedes boat traffic or entangles an unfortunate diver and causes an accident, who is going to pay? Maybe one of your workers drops a boulder on his toe whilst loading it onto your boat. All these types of questions do need considering when you embark on a project of this nature, and you may wish to take out liability insurance to mitigate your risk exposure.
Very much integrated with the objective of your reef and its design, is the choice of site location. If you are building the reef for scuba diving, then you need to consider the depth of site. Divers will need adequate bottom time, so a reef of 10-30 metres depth is sensible. Depth will also be important to ensure the reef does not become a hazard to boats and ships. Particular coral types and fish species prefer certain depths, so if you have target species for your reef, then you need to choose a site that is conducive to their preferred depth and habitat. Ecological characteristics that are conducive to good coral recruitment and colonisation rates, fish behaviour, sediment type and biodiversity are also all important factors. Others include environmental conditions such as currents and wave action, water quality, seasonality, temperature and susceptibility to storm damage. The over-riding factor however, is always likely to be cost.
Local attitudes and needs must also be considered. You may need to enforce a 'no-fishing' policy, so a nearby site that can be easily patrolled may be more practical. In many areas it will be illegal to ban fishing, so an alternative approach maybe to locate the reef inside a Marine Protected Area (MPA), or to start your own marine sanctuary. Protection and conservation of a nearby reef or a MPA can be more readily managed too, when there is a perceived risk of damage from human impact.
When considering artificial coral reef rehabilitation to repair a previously damaged reef, it's important to consider how the reef was damaged. Pollution, eutrophication, cyanide fishing, over-fishing and bleaching, leave the skeletal framework of the reef intact, so future coral reef settlement could potentially lead to reef recovery if the coral stressors were removed. This will require water analysis, and research and evaluation to ensure water quality has been restored. Dynamite or blast fishing, on the other hand, destroys the reef by shattering coral skeletons, leaving fields of shifting broken coral rubble, abrading or burying new corals, and thereby slowing or preventing reef recovery, even when the site is protected from further damage.
For reef rehabilitation efforts to be worthwhile there must be a cessation of the coral stressors, low natural reef recovery rates, adequate sources of coral larvae, good water quality and low wave and current action. A good example of a destination where reef rehabilitation was worth pursuing is the Komodo National Park in Indonesia. The area has high bio-diversity, tourism potential as a premiere world dive destination, and park management personnel who are committed to conservation and rehabilitation of the blast-damaged areas in the north east quadrant of the park.
The main job of your Public Relations officer will be to persuade the local authorities and public that the reef and its no-take zone, are in the public interest. Achieve this and you're well on your way to ensuring your reef's long term survival.
User conflict is often the main difficulty and persuading fishing boats to steer clear can be your winning formula. Often the way to do this is demonstrating in monetary terms how everyone can win. An example of how this works is the estimated damage caused by dynamite fishing in Komodo of US$ 33,000 - 300,000 per square kilometre of reef over 20 years. In all of Indonesia that amounts to US$ 570,000,000 - 3,000,000,000! Money has a way of focussing the mind, especially poor fishing communities.
You can explain that the ultimate goal of the reef is increasing coral and fish biomass, which will spread into the surrounding fishing grounds. One artificial reef manufacturer estimates that each of its units produces about 180 kilograms (400 lbs) of bio-mass each year and has an expected life of at least 500 years.
Artificial reef projects can also have further social benefits. Involving community and park rangers creates a sense of responsibility for managing and protecting resources, and educating people about the importance of healthy coral reefs. Reef projects also have an obvious tourism potential for divers and snorkellers that will bring financial rewards to local communities and local authorities.
Before going any further, individuals and dive operators should be aware of all the issues, and the environmental and legal requirements involved in the preparation and placement of an artificial reef. It's important to discuss these with the local authorities before you start. These can include shipping regulations, construction material regulations (especially when sinking shipping vessels), and marine park laws.
Now we're making progress and beginning to consider design features and the importance of design complexity, reef configuration, size, volume and area. The structural integrity and stability of the artificial reefs are obviously critical; you don't want your reef washed away on the first outgoing tide. Aspects important in targeting fish species include the provision of void space, bottom relief, reef height, light and shading. The provision of shelter through refuges and crevices is particularly important for juveniles and shellfish.
Many popular reefs, such as those at Pulau Mataking near Sipadan in Malaysia are made in the shape of a hollow concrete balls riddled with holes. Others are hollow concrete pyramids with triangular holes. In Komodo, coral was found to grow quicker on designs 70-90cm high and 140 cubic metres each rock pile. This is because coral recruitment can be significantly increased by creating stable, spatially complex structures that are high enough above shifting sediment to minimise burial or abrasion, sometimes 20 times higher than natural sea bottoms.
Who says size doesn't matter? Small plots are more likely to break apart, and tests in Komodo showed that large scale reefs with total surface areas of 1,000 square metres or more lead to quicker and more sustained growth.
Again, you may need to evaluate alternative designs and placements in order to meet your costing requirements. If budget constraints allow, you can consider electric reefs which are said to speed up coral growth through a process of electrolysis and limestone crystallisation on a conductive grid or mesh reef. This style of reef has been used in Maldives. This process is particularly useful in poor water quality locations, though you may wonder why you'd choose to build a reef in an area where the natural water quality does not support coral growth.
Materials used to develop artificial reefs must be selected that meet your primary goal of creating habitat for marine fish and invertebrates. General guidelines are that artificial reefs should create no hazard to navigation and the marine environment, and materials used shouldn't have the potential to trap divers or marine vertebrates.
Materials that pollute through leaching, physical or chemical weathering, or biological activity should never be used. Use should not be made either of materials whose disposal at sea is prohibited such as cars, untreated construction materials and tyres.
By far the most favoured reef material is concrete, including cubes, blocks and pipes, as it proves good for coral settlement and growth. However, the concrete should be mixed with fly ash to reduce alkalinity, as surfaces of high-alkaline concrete will not grow coral for more than 6 months after sinking.
Moulded and manufactured reefs are also popular. For one reef at Manado Tua Island, Bunaken, also in Indonesia, a major installation of 500 square metres of 'Ecoreefs' took place. It's hoped that these large snowflake-shaped ceramic modules will also stabilise rubble, provide structure for fish and coral, and break down over time leaving a natural reef behind.
Assuming that there is adequate coral larval supply, using limestone rocks for simple, low budget, large scale sites seems to be a viable option for restoring the structural foundation of damaged reefs. This was the case in Komodo National Park. Rocks proved to be the economically cheapest form at US$ 5 square metre in Indonesia, including materials, transport and labour.
At Pemuteran in Bali, Indonesia, an artificial reef was constructed of metal mesh with a direct current applied, using the electrolysis method described above. Even old oil rigs can be used provided nobody's view or navigation is obstructed.
Ships are often turned into artificial reefs. Organisers thoroughly clean the ships and open passageways to make marine habitats as well as safer for divers. In developed countries today, the lion's share of the expense in preparing a ship for placement is in meeting the high standards required by environmental regulators. In other countries such rigorous rules don't apply but it is still important that dive operators adhere to these requirements even when not required by local law. A poorly prepared ship can have a devastating impact on marine life. Derelict ships, in particular, contain considerable amounts of toxic substances such as PCBs, asbestos, heavy metals, lubricants, fuel and highly poisonous paint that may potentially be transferred through the food chain.
What's left after structural placement is the long, on-going task of monitoring, maintaining and safeguarding your new coral reef. You should also assess the physical condition of the reef and natural breakdown and its artificial materials over time.
In Komodo, monitoring teams measured reef growth in terms of new colony recruits per square metre. Rocks were soon colonised by coralline algae and other encrusting organisms. Scleractinian recruits had settled within the first 5 months. After 1 year, the new reef averaged 7 new corals of 7.5 square centimetre each, and 12 new colonies after 2 years. In the Maldives, a comparable reef projected achieved about 13 new recruits per square metre after 3½ years.
Access to the reef must be controlled and regulation of the fishing effort managed. Buoys can be attached for authorised users, such as divers, to reduce anchor damage, but care must be taken that the buoys do not result in easier fishing conditions. In Komodo, weekly patrols were set up to enforce the ban on destructive fishing practices. Dynamite fishing decreased by 75% and cyanide fishing and live reef fish trades also reduced. The increased law enforcement has resulted in a positive shift from low-income fishing for local markets through blast fishing, to high-income fishing for export markets.
In areas with high anthropological pressures, reef rehabilitation is more likely to be effective in conjunction with other restoration techniques such as fisheries reform and reduced fishing pressure. Given that MPAs are one of the most practical and effective methods of managing fisheries, it makes sense to concentrate efforts here in existing parks and to enforce regulations and implement alternative livelihood programmes to fishing.
The placement of artificial reefs results in the aggregation of fish. As a result, the effort required to catch fish within a particular area is decreased. When there is no regulation of the fishery, an artificial reef may have a deleterious effect on local fish populations simply by making them easier to catch. So as successful as an artificial reef programme may be, chances are it will still suffer from over-fishing, if the fishing effort is not checked. For this reason we recommend that fishing be restricted to the outlying areas that the new reef can contribute to and support. On your reef itself - no fishing, end of debate.
Transplanting corals from one reef to another has some obvious benefits as it can lead to an immediate increase in coral cover and diversity, as well as improve the aesthetics of areas frequented by tourists. It can also increase coral larvae settlement, improve the survival rate of rare or threatened coral species, and act as a means of reintroducing corals to areas which have limited larval supply or low natural growth rates.
However, such transplantations cause the obvious loss of corals from donor areas, as well as increasing the mortality and reducing the growth rates and fecundity (sexual appetite) of colonies due to the stresses of transplantation. If a site is suitable for coral growth and has a good supply of larvae, it should be able recover naturally anyway, without the need for transplantation. Unless an area is failing to recruit corals, transplantation should be viewed as a tool of last resort as physical remediation treatments and coral attachment are expensive if done on a large scale.
The strongest case for coral transplantation can be made in areas that have poor coral larval supply or high mortality rates as these areas are unlikely to recover well without assistance. Isolated inlets and bays would fall into this category, where coral reefs have been degraded due to past pollution and into which there is poor larval flow from undamaged reefs. Focus should be on transplanting slow recruiting massive species to the new community, such as porites, rather than favouring the transplanting of fast growing branching corals, such as Acropora, which recruit well naturally but tend to survive transplantation relatively poorly. Water quality will need to be good and the area needs to be a relatively low energy environment. There is no point in transplanting corals to areas where water quality is poor, or to high-energy environments such as waves and strong currents, as they will tend to die.
If the purpose of your artificial reef is to remove and rescue corals imperilled in their current location, then there are several steps to complete. These include surveying the area and documenting existing species and population sizes, developing a plan that minimises damage to coral colonies, conducting a coral propagation 'backup' by taking a few cuttings from each adult colony before rescue work to preserve genetics in case of loss, building a holding area for corals prior to planting, and performing the rescue of as many corals as is practical from the endangered area. If there's time, it's wise to give adult colonies time to heal after cuttings are taken.
Successful artificial coral reef programmes can and do make positive contributions. In Komodo at the end of the year 2004, some table and staghorn corals had reached 60-80 cm in diameter after 4 and a half years growth on an 'artificial' rock structure. On the nearby untreated rubble fields, no change in coral cover was detected after 6 years.
In Sarawak, Borneo - Malaysia, artificial reef balls have contributed to green turtle conservation efforts at the Talang - Satang National Marine Park, where illegal trawling was decimating populations. The project started 7 years ago to protect the nesting and swimming areas of the turtles, and has helped reduce the number of dead turtles washed up on the islands by 75%.
If you've got this far, then I'm sure you have come to realise that there are lots of factors to consider when making your own artificial reef. Likewise, at the same time I'm sure you appreciate it is not mission impossible either, especially now that you have this guide as a useful reference tool. Ultimately, your success will come down to the amount of planning and preparation you do, making the best use of the resources and funds you have available to you, and keeping those destructive fishermen away. One thing that no one can take away from you though, should your project fail, is that at least you will have tried and played your part in helping to preserve our prized and endangered marine environment. Good luck to you!
Some of the manufacturers of artificial reefs that you may wish to contact include Biorock, The Reefmaker, Reefball Inc, and Artificial Reefs Inc.
If you'd like to contact non-profit organisations that conduct or sponsor valuable work in the artificial reefs field, then you may like to contact Global Coral Reef Alliance (GCRA) or Project Aware. GCRA run reef rehabilitation training workshops. If you want to learn more about coral reef conservation and protection, we can recommend the ReefWatch diving programme in Krabi.
You can also help support some of the artificial reef programmes by visiting and diving the areas. Dive The World has dive travel opportunities in Komodo, Pemuteran - Bali, and Racha Yai Island, Phuket - Thailand.
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