A view of Grahams Harbor from the air. See other beautiful phenomena from the Bahamas.
A relatively simple solution to a potentially substantial problem, artificial reefs (ARs) provide means for local communities as well as large countries around the world to take action immediately when coral reef damage or loss occurs. Coral reefs are declining rapidly, due to “destructive fishing and pollution (top two),” as well as ship groundings, natural disasters, ocean acidity and much more (Calvert, 1995). The creation and installation can provide temporary habitats for fish, substrate or surface to mobile polyps and protection from further damage to existing corals reefs. As politics and legislation often take time to enact and solutions are slow to be created, non-governmental organizations and scientists can readily use ARs. As important as taking the initiative to install ARs, the site selection, management techniques, choice of materials, and the consideration of existing ecology of the marine environment is very important.
So, why are coral reefs important in the first place? Coral reefs are an intricately woven ecosystem that accommodates the greatest diversity of life in the ocean. They provide habitats for organisms, nurseries to young, cleaning stations for fish, storm protection for people living on the coast, and more. Without coral reefs many of the fish/mollusks eaten in restaurants would no longer be available (oceanworld.tamu.edu). The already devastating damage of hurricanes and tropical storms could be worse if it were not for coral reefs that break up waves and strong currents. Coral reefs are also important in controlling the carbon in the upper water column, which is particularly important as atmospheric carbon dioxide, CO2, increases.
“Ten percent of the world's reefs have been completely destroyed. In the Philippines, where coral reef destruction is the worst, over 70% have been destroyed and only 5% can be said to be in good condition.” - oceanworld.tamu.edu The number is now closer to 20%+ as stated by, Dr. Joanie Kleypas of the National Center for Atmospheric Research.
In our group project our hypothesis states that, “the more structurally complex a reef is, the greater the species diversity will be. It will also become established at a faster rate than a simpler reef.” As stated by Calvert, 1995, “It is important when constructing the (artificial) reef to provide as much diversity (complexity) of habitat as possible, as this encourages the greatest diversity of species.” Diversity is important as a coral reef system as it can be an indictor of overall reef health. Greater diversity equals greater health.
To start, the site selected for AR construction should orientated such that it is across the current, or perpendicular to the current flow (Calvert, 1995). Calvert’s reason for this orientation is simple. The orientation provides a barrier from the current that protects smaller, younger species as well as providing nutrient upwelling as the current stirs sediment from the sea floor when passing over the AR. The greater number of crevices in addition to their varying sizes provides fish and other organisms, protection from the elements and predators alike. Crevices also provide places for fish and mollusks to lay their eggs.
To also help determine the placement of ARs, the relative mean height in which they extend from the sea floor is also important. Mean height refers to the average water column depth between high and low tides. The rule according to Calvert, 1995, is approximately, “one-third of the water depth.” Calvert continues to explain that predatory fish can more easily locate higher ARs and in turn greater biodiversity can be attained. The idea is to mimic previously existing or currently imperiled coral reef ecosystems, where ARs can be constructed in a “known” area of coral habitat. An AR would most likely not be placed in areas where coral reefs never existed in the first place. An example of good placement would be in an area where a recent ship grounding decimated parts of an existing coral reef.
So an extremely important factor in deciding AR placement is what caused the coral reef damage or stress in the first place. If the area in question is suffering from poor water quality efforts the start placement determination efforts might more productively be spent on planting mangroves or removing point-source contaminants. In some instances, rebuilding supporting habitats, conditions or ecosystems could be the first place. Another example would be a rapid increase of the Crown-of-thorns starfish that in great numbers, could literally digest an entire coral reef if not kept in balance. The balance to this threat is to ensure predatory fish to the starfish are healthy in numbers.
The placement of the ARs can often be selected by talking to local fisherman. Fishermen are usually intimately familiar with areas of fish productivity, average water depth, reef structure and in many cases where old reefs once existed. The use of such knowledge can serve dual purposes, 1) local communities have a control in reef construction and 2) a vested interest in managing the ARs as they grow.
Management techniques by local communities further ensures the success of the ARs. If not for the simple reason that the ARs success could mean better survival of the people as more fish begin to inhabit the area. Historically in most conservation efforts, it is the local people’s support that strengthens conservation success potential. Such as, Costa Rican support of sea turtle conservation instead of eating the sea turtle and the turtles’ eggs. The reef in the same analogy must be looked after with steward programs, because dynamite fishing of cyanide fishing practices could wipe out all intended benefits of AR construction. In addition, inherent in the involvement of the local community for management purposes, the investment of educating the community is extremely important.
Techniques used to manage constructed ARs can be fish counts and surveys, formal bottom surveys, water quality analysis and monitoring, beach profile measurements, photo documentation of coral growth rates, participation on specific scientific studies, angler counts, stability monitoring, GPS coordinate verifications, and documenting events such as coral or fish spawns. Examples of organizations that perform some or all of these functions around the world are, Reef Check and the Reef Environmental Education Foundation.
The selection of materials is almost as open as one’s creativity. The main considerations for materials are, potential toxicity of material in the water or as it breaks down, potential to collapse with time or a weak infrastructure, and understanding, what if any other negative consequences could occur; for instance using oil drums that pollute the water and they rust quickly in the marine environment. Materials historically used include: coconut stumps, old tires, old ships (wooden is no longer legal to use in some instances), steel modules, concrete modules, well rings, granite boulders, bottles and almost anything else found locally. To attain the height suggestions mentioned previously, concrete and/or metal poles can be used or even floats or buoys tied to the AR structure. This myriad of choices makes artificial reef construction easier for economically developing areas of the world and often times can turn garbage into environmental conservation.
Once in place, ARs can have coral larvae settle or colonize the surface of the artificial material. Also popular to quickly establishing reef building coral is transplantation of fragments of the coral for propagation. Transplantation refers to the removal of a fragment (piece, such as a branch of Acropora) from an existing coral structure and moving to an AR surface whereby the fragment is cemented in place to grow, or propagate. When selecting fragments the coral to be transplanted should live in similar conditions to the area where it will be moved. The conditions include, water depth, light intensity, water movement of current, water quality, water turbidity and dietary requirements.
One such system developed in 1988 by Aharon Miroz (Head Curator of Coral World International) takes into consideration many of the important factors as mentioned and he lists the benefits of transplantation as follows:
1. Control in coral fragment placement while maintaining mutual relations between genii and species of corals in order to avoid predation and competition.
2. Construction of a coral reef at any depth of an area of the ocean (in which coral normally live).
3. Immediate population by coral dwellers.
4. The reef is constructed in time for the juvenile fish and invertebrates of that season to find accessible and inviting habitat.
5. Construction of an already colorful and attractive reef.
6. Opportunity for multi-annual follow-up of each coral.
7. The time-saving factor allows within a short period the construction of an almost natural and complete coral reef.
Corals grow relatively slow in human terms, from >1mm/yr to 20cm/yr (Downtown Aquarium Seminar, Denver, Colorado). So, fragment transplantation can speed up the AR colonization and success by many tens of years.
The consideration of existing ecology is often a difficult task. In the book, Ecological Engineering and Ecosystem Restoration, by William J. Mitsch and Sven Erik JrŅgensen there are two approaches to Ecology: a Reductionistic Approach and a Holistic Approach. The Reductionistic Approach looks at relationships one at a time and then pieces them together to form an idea of the entire ecosystem. The Holistic Approach takes into account the entire ecosystem and tries to understand relationships on many levels. Reductionistic Approaches are commonly found in scientific articles, such as phosphate availability and resulting algal blooms. The missing component to this view is the often the answer to as why phosphate may, or may not, be available (for example). The challenge of exploring ecosystem questions with the Reductionistic Approach is that organismal behavior and many of factors can not be adequately considered (Mitsch and JrŅgensen, 2004). This is where the Holistic Approach becomes the most valuable tool.
The Holistic Approach transcends the challenge of relating simple organismal relationship experiments on laboratory levels to whole ecosystem(s). In a study by Ahn and Mitsch, 2002, showed that when comparing a wetland ecosystem 10,000 m2 to a wetland mesocosm, 1 m2, “mesocosms, with their simple structure compared to full-scale ecosystems, was able to replicate some functions fairly accurately but that rates of biogeochemical were quite different at different scales.” An important point made by, Mitsch and JrŅgensen, 2004, was that organisms function differently in relation to other organisms and other environments when studied; such as a laboratory and in isolation.
This Holistic Approach translates to understanding as much as we can about the surrounding, existing and/or past ecosystem as a whole. If ARs are created, but over fishing keystone species to the area continues the coral reef community may continue to suffer. If the human influences hindering coral growth, such as anchoring on the reef, are not remedied, destruction will continue. Allen, 1988 states it beautifully when talking about assessing the entire ecosystems when he stated, “Everything is linked to everything,” and “The whole (ecosystem) is greater than the sum of the parts.” His discussion begins with these two ideas that, as I try and interpret, the Reductionistic Approach is useful when looking at some ecosystem specifics, but can only be valuable when also considered in conjunction with the Holistic Approach. Since there are hierarchies of ecosystem diversity, macro and microscopic, all considerations are hard to attain. The hope is that enough consideration to the ecosystem components yields a positive result in creating ARs to restore the coral reef.
In the book, Coral Reef: Restoration Handbook, edited by William F. Precht there are many approaches to restoring a coral reef, but the goal of ARs are to:
1) Mitigate for reefs damaged by anthropogenic activity
2) Alter currents
3) Restrain rubble
4) Restore habitat by providing substrate and refuge for fish, coral and other reef organisms
5) Conserve biodiversity
6) Provide aesthetically pleasing structure(s) for tourism
And, “The goal of an artificial reef installation that concentrates on restoring corals is to establish a stable, waver-resistant, fixed substrate that provides refuge, where corals can recruit and/or be transplanted. The refuge provided by such an artificial reef enhances fish and invertebrate communities.”
In Florida, “The Florida Fish and Wildlife Conservation Commission (FWC), Division of Marine Fisheries, Bureau of Marine Fisheries Management administers a state artificial reef program that was legislatively created under s. 370.25 Florida Statutes in 1982.”
As chosen by this Commission, the goals are:
1) Enhance private recreational and charter fishing and diving opportunities
2) Provide a socio-economic benefit to local coastal communities
3) Increase reef fish habitat
4) Reduce user conflicts
5) Facilitate reef related research; and,
6) While accomplishing objectives 1-5, do no harm to fishery resources, Essential Fish Habitat (EFH), or human health.
As summarized by the, Reef Ball Volunteer Services Division, there are ten basic steps for restoring coral reef functions by way of ARs:
1) Protection and Conservation: Sometimes, reefs just need to be left alone to recover from human impacts. Designating and protecting al reef as a marine protected area can have restorative effects. There are a host of governmental and non-governmental organizations actively working to conserve coral reefs...support them.
2) Restoration of Water Quality: Water quality has been deteriorating worldwide and is one of the main causes of decline of function in coral reef ecosystems. There are a wide range of activities from stopping point sources of pollution to providing habitat for filter feeders that can be used to improve water quality near coral reefs. The first step is to identify water quality issues, then work to bring back, as closely as possible, water quality to its natural state.
3) Active Management: Reefs can recover more fully and faster when they are actively managed. This may require decisions such as installation of mooring buoys, fishing regulations, enforcement of environmental laws, etc.
4) Restoration of Habitat Complexity: In the case of coral reefs that have been destroyed by storms, ship groundings or other loss of complex hard substrate, designed artificial reef modules can be used both to provide a suitable base for the hard corals to recruit onto for natural recovery and to provide habitat for fish and other life that need habitat complexity for survival. Advanced designed artificial reefs can incorporate a variety of special features such as larval recruitment aids for fish or lobster, fish spawning pinnacles, special surface textures to enhance coral settlement, and can be built in a variety of sizes, layout patterns, etc. to best mimic the reef that was lost.
5) Rescue of Imperiled Corals. In some cases, it is possible to predict the death of coral colonies or other marine life such as in the case of impending construction or other known threats. These corals can be transplanted to a safe area, or they can be propagated into many more new colonies. Usually in coral rescues it is advisable to propagate enough individual fragments from each colony so that if a coral is lost in transportation or replanting then the genetics of the colony can still be retained from propagates.
6) Recovery of Interconnected Systems: In many cases, coral reefs can loose function because adjacent habitat which is interconnected with the reef is lost or damaged. Mangrove systems (and in particular Red Mangroves) provide an interconnected "nursery" grounds for many coral reef species. Therefore, they can be replanted in areas where they have been lost or in areas suitable for reef health. Sea grasses are also often threatened near reefs and have similar interconnections with reefs.
7) Propagation and Planting Corals: In some cases, corals need to be re-planted to have a recovery. There may be reasons why coral larval are unable to settle in an area or the speed at which recovery takes place may not be fast enough by natural growth to recover the coral reef system. The Reef Ball Foundation has developed a special team of volunteer experts that can train local volunteers to propagate and plant corals with a high level of success (usually 80-100% survival of fragments with 100% survival of coral colony genetics). The methods used are less expensive and less labor intensive than previously used methods. For example, over 10,000 coral colonies were propagated and transplanted in a 14 day period using 15 volunteers in our most recent project.
8)Monitoring & Education: Reefs can recover better when people are educated about the importance of reefs and when people have good facts to be able to make better management decisions. There are a large variety of monitoring and educational programs that can aid the recovery reef systems. Active monitoring programs can, for example, find and treat coral diseases or alert managers to new threats.
9) Engage the Scientists: Scientists are constantly studying new methods and techniques to aid our coral reef systems. In working with scientists, we can advance our knowledge and understanding of how reef systems function to aid in their recovery.
10) Take Action: Even though we can't fully restore coral reefs, we can't just give up efforts either...coral reefs are worth protecting and they are worth the efforts to help them recover. If you know of a reef that has been damaged or will be damaged, let us know....there are many ways we can work together to save them.
Our group project attempted to demonstrate the seemingly already known fact, that AR complexity leads to more organism diversity. It is my opinion that site selection dictated the rate in which habitation occurred, and time, or not enough of it, was our only limiting factor in provided the statistical data to support our hypothesis.
We created 9 ARs of three different complexities; simple, medium and high. The three reefs were placed approximately 44 meters off shore in a mean depth of 1.5 meters perpendicular to the shoreline and current. The created ARs were placed starting 5 meters from an existing, large AR structure, and placed 5 meters from one another starting from simple, medium, complex, simple, medium, complex, simple, medium and lastly complex.
The simple complexity AR materials include:
- 1 Glass Bottle
- 1 Milk Crate
- 7 Conch Shells
The medium complexity AR materials include:
- 2 Glass Bottles
- 1 Milk Crate
- 7 Conch Shells
The high complexity AR materials include:
- 2 Large Rocks
- 10 Glass Bottles
- 1 Milk Crate
- 6 Conch Shells
- 1 Tire
- 13 Coconuts, 6 tied together and tied to the crate to float suspended and 7 inside the tire
The species identified were:
- French Goat
- Fairy Basslet
- Slippery Dick
- Banded Butterfly
- Goat Fish
- Sea Urchin
- Four-eye Butterfly Fish
- Pygmy Seabass
The presented findings of our group showed that there was not statistically relevant data when calculated by the JMP software. The graphical display does however show trends of increasing diversity and habitation rates over the 5-day time period. The first AR to be inhabited was the one closest to the existing AR of simple complexity. Our choice of materials could not have been better. Site placement and time were our biggest challenges.
Sources of error included in our group presentation are but a few of the considerations easily remedied by simple research into AR design and planning. The fact that there are many things that we did correctly, although maybe by scientific instinct, such as accurate current placement, selection of materials and even management (short-term) strategies, shows our ability to formulate and execute a successful AR program in a matter of days.
In conclusion, the complications of ARs are inherent in that it is constructed to replace, temporary, natural ecosystems. The benefits of the ARs need work, planning and good management. The exact same things can be said about natural coral reefs, but the general public either does not understand the benefits and/or takes the incredible benefits and marine life for granted. Manage of coral reefs will need greater and greater attention and resources in the year to come and I hope that our government will aid the people working to preserve an endangered environment.
Ahn, C. and Mitsch, WJ. 2002. Scaling Considerations of mesocosm wetlands in simulating large created freshwater marshes. Ecological Engineering. 18:327-342.
Allen, PM. 1988. Ecology, thermodynamics and self-organization: towards a new understanding of complexity. Ecosystem Theory for Biological Oceanography, Canadian Bulletin of Fisheries and Aquatic Sciences. 123:3-26.
Calvert, P. 1995. Artificial Reefs and Their Placement. Appropriate Technology: Vol. 22, number 2.
Dodrill, J. 2005. Artificial Reef Summary Program Overview. FWC DIVISION OF MARINE FISHERIES BUREAU OF MARINE FISHERIES MANAGEMENT.
Downtown Aquarium Seminar, Denver, Colorado. 2003.
Edited by William F. Precht. 2006. Coral Reef Restoration Handbook. Taylor and Francis Group.
Mitsch, WJ and JrŅgensen, SE. 2004. Ecological Engineering and Ecosystem Restoration. John Wiley and Sons, Inc.
Long Island Artificial Reefs:
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