Coral reef restoration with Reef Balls

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Lion Fish on a newly deployed Reef Ball

Cover photo: Lion Fish makes itself at home in a newly deployed Reefball


In the course of numerous dives in and around coral reefs in the Capital Area of Oman, the divers of the Ras Al-Hamra Sub Aqua Club (RAHSAC) became aware of the environmental pressure imposed by human activities on these fragile environments. In an effort to reduce the damage to coral due to anchoring of boats for recreational diving and snorkelling activities, the club encouraged the installation of permanent mooring buoys at several popular sites around the island. As a result, mooring buoys were installed at six different locations over the course of 1997 with sponsorship from Petroleum Development Oman (PDO).

In a further effort to positively contribute to the preservation of coral reefs, RAHSAC now wishes to proceed with a project involving the construction of an artificial reef south of Fahal Island using the best technology currently available. The main aim of the project is to establish the feasibility of restoring existing but damaged coral reefs and the creation of new recreational coral reefs and reefs for commercial fishing in the Oman waters. The project is a direct contribution to the implementation of Oman’s ambitious coral reef management plan.

RAHSAC has obtained information from the Reefball Development Group in Florida on their method of artificial reef construction which is claimed to be the most advanced in the world. The dive club also obtained equipment and an unlimited license to build their own Reefballs based on the patented concept. In agreement with the Ministry of Environment and Regional Municipalities (MRME) and in close collaboration with the Sultan Qaboos University (SQU) a pilot project of reef restoration using the Reefball concept has been developed. The pilot project will be sponsored by PDO and executed over a period of 24 months. Based on the results of the pilot project, additional reefs may be developed on a larger scale.

Preparing the mould: holes are created by filling the mould with easily deflated balloons/buoys.


As a result of increased environmental pressure, the overall diversity and extent of many coral reefs have declined over the years. The destruction of coral reefs is a very complex ecological process involving direct physical destruction by anchors and fishing nets, and to a lesser degree recreational diving activities, in addition to indirect processes such as, on a local level, pollutants and sedimentation, and on a global level, temperature increases, Ultra Violet radiation and meteorological variations.

In addition, data indicates that despite a considerable increase in fishing activities over the last 10 years, the yield of coastal fishing has not increased by the same proportion. This suggests a high risk of over-fishing in coastal zones which are rich in coral reefs.

Artificial coral reefs have been tried at many locations in the world and have received considerable attention from the scientific community. Many substrata have been used—from old cars to complex structures in stainless steel and concrete—to attract sea life and enhance bio-diversity. An example is the artificial reef project comprising of tyres and concrete pipe materials installed in the Mina al Fahal bay during 1997, as an experimental PDO/MRME project. Initial conclusions of this experiment show that tyres form an attractive habitat for fish but are not suitable for long term reef restoration because of their relative toxicity and instability. The concrete pipe has not developed diversity due to the pH and other properties of the concrete itself.

A major advantage of the Reefball concept proposed in this project, is that the design of natural reefs is simulated by an arrangement of large (1m * 1.2m) "spheroid" structures in concrete which can withstand extreme weather and physical impact. The characteristics of the concrete (chemistry and surface roughness) has been modified to facilitate invertebrate settlement. The use of micro silica during fabrication, allows the pH of the concrete mixture to be adjusted to that of sea water which in turn promotes coral growth and prevents structural breakdown due to sea water saturation. This gives the Reefballs an estimated life-span of over 500 years.

Also the Reefball concept offers modularity allowing a few or many Reefballs to be deployed at any time and existing sites to be expanded. Alternatively, in the unlikely event that the artificial reef shows a negative effect on other reefs in the area, e.g. an increase of coral eating fish, the Reefballs can be relocated.

The finished product: the concrete is carefully designed to be pH-neutral.

Project Objectives

This artificial reef project, named "Pro-Creator" as an abbreviated form of Project Reef Creator Oman, is designed to answer several questions concerning coral reef preservation and restoration.

It addresses four main aspects of coral reef development:

  1. methodological testing of an artificial reef structure;
  2. reef corals settlement;
  3. fish population enhancement;
  4. global bio-diversity.

The first component aims to identify whether artificial reefs using Reefballs actually work in the extreme conditions of Oman (high temperature, high salinity and extreme fluctuations of temperature). It also aims at identifying construction costs and the evolution of the used materials over time.

The next three components will identify the forcing factors responsible for the well documented "artificial reef" effect usually measured by an increase in bio-diversity and an increase in biomass of reef organisms.

This pilot project is designed to identify more particularly the effect of depth and seasonality on invertebrate settlement.

If Reefballs have to be used in more extensive rehabilitation programmes for instance, it is essential to identify the ideal periods of settlement for the main groups of colonising species such as coral, barnacles and algae. It is also important to identify the structure of the newly settled "Reefball" community and to compare it to "normal" reef communities and later analyse the potential risk involved in using artificial structures.

The site selection for this pilot project, the deployment of Reefballs, and the monitoring of the artificial reefs are further described below.

Site Selection

Two sites in a considerably degraded area at the South side of Fahal Island have been selected for this pilot project. These sites, each measuring approximately 20m * 20m, are shown below:

Fahal Island sites

The selected sites used to support a flourishing Pocilloporid assemblage of corals but appears to have been destroyed over the years with a remaining coral cover of less than 5%. No or little re-growth have been observed in this area. A possible cause is the continuous scouring of the newly settled colonies by the large size sediment resulting from the coral death. Other zones of the reef in the same global area are largely intact and support high coral cover (> 60 %) and high bio-diversity.

In the selection of these sites, sandy areas were avoided to limit the amount of sand scouring which may adversely affect the survival of new coral recruits. The sites were also chosen to be within the optimal growth zone for reef corals (2-15m in depth). To identify the effect of depth, site 1 is at a depth of 4-6m and site 2 is at a depth of 10-12m.

Reef-Ball Deployment And Monitoring Programme


The pilot project comprises the installation of forty Reefballs over a one year period.

Five Reefballs will be installed by RAHSAC at each site over four equally-spaced periods during October-November, January-February, April-May and July-August to cover the four seasons corresponding to spring, summer, fall and winter. The balls will be randomly distributed over the two sites with a space of approximately 2.5 m between the balls to allow freedom of movement by divers during the monitoring activities.

At each sites several small sample blocks of concrete will be immersed at the same time to monitor the chemical evolution (pH) of the concrete structure. This aspects of their chemistry is extremely important, especially for sensitive species such as reef corals. The samples will be collected by SQU divers to measure the pH evolution and the rate of benthic micro-algae settlement.

Monitoring of Coral Development

The Reefballs themselves will be thoroughly examined by RAHSAC and SQU divers at regular intervals during the coral development. Two surfaces on each Reefball will be permanently marked by a pair of camera mounting holes in the concrete surface and plastic marker tags. The two marked surfaces will be used to analyse settlement and growth patterns. They will be photographed using a video camera, 1, 2, 5, 9 and 12 months after deployment by RAHSAC divers. The videos will be analysed in the SQU laboratories and the position of macroscopic sessile organisms such as sponges, soft coral colonies, and hard corals will be recorded to follow growth and mortality over time.

Monitoring of Fish Population

The two sites will also be extensively videoed at two month intervals by the RAHSAC divers to monitor the development and evolution of the fish community. Control zones located in the same area but devoid of Reefballs will also be videoed. Based on the videos images, SQU will calculate diversity indices and fish specific abundance in and around the artificial reef but also in the control zones away from the artificial reef. Special attention will be paid to juveniles of commercial species in order to investigate the potential of Reefballs as a device to enhance recruitment of fish for commercial fishing purposes. To achieve this, fish larval traps, specially developed to study coral reef fish by the Australian Institute of Marine Science, will be deployed at both sites 2 to 3 times every season.

Monitoring of Algae

Some Reefballs will be equipped with removable algae settlement plates. The algae settlement plates will be collected by SQU divers at regular intervals for assessment of algae settlement, growth pattern and taxonomy. The samples will be analysed at SQU and at the Marine Science and Fisheries Centre. Any plate removed will be replaced to follow settlement pattern over time. The same plate will also be used to identify settlement patterns of small invertebrates (worms, barnacles and corals).

Monitoring of Sea Water Temperature

Temperature logging at the Fahal Island sites will be conducted by SQU to link the observed pattern of settlement with environmental changes such as tidal cycle, the up-welling cycle and meteorology. A recording thermograph with a resolution of 0.001 °C and time resolution of 2 minutes will be placed inside one of the Reefball structures.

Reef Ball 3 days after deployment

A Reefball in-situ: Within three days of being submerged,
growth was visible and fish were sheltering inside.
(diver: Managing Director Brian Ward)

Potential Benefits Of The Project

Scientific benefits

The project offers several scientific benefits for understanding the marine biology in the Oman waters and offers unique research opportunities to post graduate students at the Sultan Qaboos University and to MRME staff. Such staff will be delegated specific practical parts in the monitoring programme which has been designed particularly to provide:

Benefits to the Community and Involvement

To make a proper assessment of the Reefball’s potential to restore coral reef structures and create fishing reefs, the human disturbances should be minimised. It is very important to the success of the project that no fishing activities take place within a 50 meter radius of the new artificial reefs. To achieve this, it is recommended that a program is implemented which explains the local fishing communities the purpose of the project, its potential long term benefits and the reason for the fishing restriction.

Direct benefits to the local community and the world as a whole are:

Post Pilot Development

The post pilot development of Project Reef Creator depends on the findings which will follow as a result of a two year monitoring programme. A progress report will be prepared by SQU every six months from deployment of the first Reefballs. The second report will also address the need for a spatial extension of the programme at other sites with contrasting environment. A final report documenting the findings will be prepared by SQU after 24 months and circulated to the concerned authorities. The various contributors to the project will assess the success of the artificial reef and will call for further extension or termination as appropriate.

Project Reef Creator Oman (page 2)

This information provided by the (RAHSAC) OMAN Pro-Creator Website

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