Marine Electrolysis for Building Materials and Environmental Restoration

Thomas J. Goreau, 2012
p. 273-290 in Electrolysis, J. Kleperis & V. Linkov (Eds.), InTech Publishing, Rijeka, Croatia
Additional information is available at the end of the chapter

1. Introduction

Within weeks after Alessandro Volta developed the battery in 1800, William Nicholson and Anthony Carlisle applied it to the electrolysis of water, producing hydrogen at the cathode and oxygen at the anode, and thereby showing that water was not an irreducible element, as had been thought, but a chemical compound made up of two elements with very different properties. It was quickly found that adding salts to the water greatly accelerated reaction rates. We now know this is caused by increased electrical conductivity and reduced resistivity, thereby increasing the electrical current flowing for a given applied battery voltage according to Ohms’’s Law. Humphrey Davy soon applied electrolysis to the practical problem of oxidative corrosion of copper plates used to sheath ships and protect the wood from boring organisms, founding the field of galvanic protection of metals from corrosion, now widely used to protect steel ships, oil rigs, bridges, and subsea pipes from failure. Seawater electrolysis for galvanic protection can use sacrificial anodes, driven by the voltage potential difference between different metals, or actively impressed currents driven by a battery or a direct current power supply. In the first case the voltage differences are small, usually only tenths of a volt, according to the difference in electromotive potentials of the various metals or alloys used. The metal acting as the cathode is completely protected from rusting and corrosion as long as the electrical current flows. The metal acting as the anode usually dissolves away as the reaction proceeds, and needs to be periodically replaced in order to continue to prevent corrosion of the cathode. Increased currents accelerate reaction rates, which can cause mineral growth or scale, something most uses of cathodic protection wish to avoid. For example, if a boiler is being cathodically protected from rusting, one does not want to precipitate a mineral scale layer on it, because that is less thermally conductive than the metal, and reduces heat transfer and boiler efficiency. Therefore most uses of cathode corrosion protection use the lowest possible voltages and currents needed to prevent rusting, in order to avoid growth of scale.

There is a ““natural”” analog of cathode protection that is crucial for marine archaeology. A shipwreck invariably contains objects of several different metals, such as various steel alloys, copper, brass, bronze, aluminum, and others. The metal that acts as the strongest anode, according to its electromotive potential, proceeds to dissolve, releasing electrons that flow to the cathode metals, protecting them from oxidation. When the anode has completely dissolved, the next metal in the electromotive series then plays that role until there are no more anodic metals left, and at that point corrosion can take place on the last cathode metal. The process causes growth of limestone scale on the cathode, which protects and conceals it. Metal artifacts preserved in marine shipwrecks have been protected because they acted as cathodes. Despite the popular image of treasure hunters finding shiny golden coins, in fact the treasure is completely encrusted in limestone, appearing as irregular white crystalline lumps with the metal surface completely concealed. The first thing marine archaeologists do with these lumps is to throw them into an acid bath to dissolve away the limestone, in some cases speeding the process up by wiring them up as an anode of a battery, although that risks destroying the artifact if it proceeds too far. Only once the limestone has dissolved can the archaeologist see the metal artifact.

Later applications of aquatic electrolysis included making chlorine and bleach (sodium hypochlorite) from seawater and chloride brines, and purification of metals, but largely under highly controlled conditions in limited volumes, often from fused salts or acid solutions rather than from seawater. Following the First World War, the Nobel Prize winning German Jewish chemist, Fritz Haber, whose work on industrial nitrogen fixation via the Haber-Bosch process is the basis for almost all fertilizer nitrogen production, and hence for our global food supplies, sought to use electrolysis of sea water to extract traces of gold from the ocean to pay back war reparations imposed by the victors. He found that concentrations were too low to be economic, and was then hounded to death by the Nazis.

2. Physical properties of mineral production from sea water

Michael Faraday was the first to precipitate solid minerals by electrolysis of seawater. It was not until 1976 that Wolf Hilbertz recognized that these minerals, under the right conditions, could be a resource rather than a problem to be avoided. Hilbertz, an innovative architect working on self-growing construction materials, experimented with electrolysis of sea water and discovered that by varying the voltage and current applied he could grow different minerals on the cathode, ranging from soft to hard (Hilbertz, 1979). His inspiration was biological: if marine organisms could grow shells and skeletons of precisely controlled architecture from minerals dissolved in seawater, we should be able to figure out how to do so as well. Limestone does not precipitate naturally from seawater, so marine organisms must use their metabolic energy resources in order to create special internal chemical conditions that cause shell growth.

Hilbertz found that under low electrical current conditions he could grow extremely hard calcium carbonate limestone deposits, made up of crystals of the mineral aragonite, the same compound that makes up coral skeletons and the bulk of tropical white sand beaches.

Higher currents caused the growth of the mineral brucite, or magnesium hydroxide, which is soft and tends to easily break off. Through experimentation it proved possible to grow rock-hard limestone coatings of any desired thickness on steel frames of any desired shape or size, at up to 1-2 cm per year, with compressive (load-bearing) strength up to 80 Newtons per square millimeter (MegaPascals), or about three times the strength of concrete made from ordinary Portland Cement.

This material, which Hilbertz first called ““Seacrete”” or ““Seament””, is now called ““Biorock®”” in order to emphasize that this is the only GROWING marine construction material that gets larger and stronger with age, and is self-repairing, like biological materials, but unlike any other marine construction material. This unique property causes any damaged or broken portion to grow back preferentially overgrowth of undamaged sections.

Biorock materials Ihuru, North Male Atoll, Maldives
Figure 1. Biorock materials grown at Ihuru, North Male Atoll, Maldives, around a 6mm diameter steel bar in approximately one year. The darker surface color is a thin film of dried algae that migrates on the surface as it grows outward, leaving the interior bright white. The piece was hacksawed out of a growing structure. There is no corrosion at all on the steel. Photograph by Wolf H. HIlbertz.
Biorock materials from various locations
Biorock materials from various locations. The piece at mid-left is the one shown in the previous photo. The one at top-left, completely overgrown with oysters, is from Louisiana, and all the rest were grown in a two and a half year period at Ihuru Island, North Male Atoll, Maldives. Samples tested from that set of samples in the Materials Testing Laboratory of the University of Graz, Austria, had the compressive strength of 60-80 Mega Pascals, around three times the load-bearingg strength of ordinary Portland Cement concrete. Photograph Wolf W. Hilbertz.
Biorock material piece was cut near where two steel bars crossed
Figure 3. This piece was cut near where two steel bars crossed. We had wedged a coral between the bars after a few months of growth. The coral skeleton is the slightly darker vertically oriented area in the center. After 2.5 years it was completely overgrown and encased by electrochemically produced minerals. Photograph Wolf H. Hilbertz.
Pemuteran, Bali Biorock self-repair
Pemuteran, Bali Biorock self-repair
Pemuteran, Bali Biorock self-repair
Pemuteran, Bali Biorock self-repair
Pemuteran, Bali Biorock self-repair
Pemuteran, Bali Biorock self-repair
Pemuteran, Bali, Biorock self-repairing material

Figure 4. Self repair of Biorock damaged by big boat impact. Time series photographs by Rani Morrow-Wuigk. This structure was installed in June 2000. Note there is no rust on the steel after nearly 11 years
in seawater.

The remarkable property of self-healing structures results from the distribution of the electrical field. Initially the electrical gradient between the anode and the cathode results in growth of mineral layers all over the cathode, starting at the closest points, or at sharp extremities that focus electrical field gradients, or at sites where water currents preferentially transport electrons.

Unlike the steel, the minerals are poor electrical conductors, and act as partial insulators. Nevertheless, electrons continue to flow because of the imposed electrical gradient. Although the electrolytic reactions generate hydroxyl ions and alkalinity in the water that are neutralized by mineral deposition taking place at the surface of the metal (see next section), production of hydrogen gas at the cathode surface causes creation of tiny pores and channels from the metal surface to the seawater, out of which hydrogen bubbles emerge (such bubbling provides visible proof that the reaction is working properly). Even Biorock material with three times the load-bearing strength of ordinary concrete has around 20% porosity. While it might be thought that minerals might insulate the cathode and prevent further growth, the imposed electrical gradient ensures that growth continues, in part because electrons flow through the hydrogen escape pores. We observe no long-term decrease in the rate of bubbling or the growth of minerals, even in cases where more than 30 cm of hard minerals have grown over the cathode.

When the mineral growth is broken off, whether by severe storm wave damage, boat impacts, or deliberately by pliers, hammers, or hacksaws, and the bare metal is exposed, there is greatly increased growth at that point, until the newly deposited minerals are as thick as adjacent unbroken material. The metal is all at the same voltage potential, but reduced or absent mineral coatings cause the increased electrical current and mass transfer to flow through the water at that point. When the newly grown material is as resistive as the old coating the increased growth rate is self-limiting. In some cases new material is more porous due intense hydrogen bubbling, and the repaired area may grow thicker than adjacent harder and less porous material. We first recognized this focusing of current to freshly exposed surfaces in an experiment using multiple lengths of rebar as cathodes. We would periodically remove one rebar in order to measure the thickness of the material growth, replacing it with a fresh rebar, in an attempt to measure long-term growth rates and changes in chemical composition. The bare steel surface focused the current on the new rebar, which grew at the expense of all the others, stopping their growth. While the experiment did not work as intended, it provided valuable insight into the process.

3. Chemical mechanisms of mineral deposition Read More: Marine Electrolysis for Building Materials and Environmental Restoration

Blue Planet Laureates Speak Out

This paper is a synthesis of the key messages from the individual papers written by the Blue Planet Laureates (Annex I describes the Blue Planet Prize), and discusses the current and projected state of the global and regional environment, and the implications for environmental, social and economic sustainability. It addresses the drivers for change, the implications for inaction, and what is needed to achieve economic development and growth among the poor, coupled with environmental and social sustainability, and the imperative of action now. The paper does not claim to comprehensively address all environment and development issues, but a sub-set that are deemed to be of particular importance.

To read the whole paper:

Key Messages

  • We have a dream – a world without poverty – a world that is equitable – a world that respects human rights – a world with increased and improved ethical behavior regarding poverty and natural resources – a world that is environmentally, socially and economically sustainable, where the challenges such as climate change, loss of biodiversity and social inequity have been successfully addressed. This is an achievable dream, but the current system is deeply flawed and our current pathway will not realise it.
  • Population size and growth and related consumption patterns are critical elements in the many environmental degradation and social problems we currently face. The population issue should be urgently addressed by education and empowerment of women, including in the work-force and in rights, ownership and inheritance; health care of children and the elderly; and making modern contraception accessible to all.
  • There is an urgent need to break the link between production and consumption on the one hand and environmental destruction on the other. This can allow risking material living standards for a period that would allow us to overcome world poverty. Indefinite material growth on a planet with finite and often fragile natural resources will however, eventually be unsustainable. Unsustainable growth is promoted by environmentally-damaging subsidies in areas such as energy, transportation and agriculture and should be eliminated; external environmental and social costs should be internalized; and the market and non-market values of ecosystem goods and services should be taken into account in decision-making.
  • The immense environmental, social and economic risks we face as a world from our current path will be much harder to manage if we are unable to measure key aspects of the problem. For example, governments should recognise the serious limitations of GDP as a measure of economic activity and complement it with measures of the five forms of capital, built, financial, natural, human and social capital, i.e., a measure of wealth that integrates economic, environmental and social dimensions. Green taxes and the elimination of subsidies should ensure that the natural resources needed to directly protect poor people are available rather than via subsidies that often only benefit the better off.
  • The present energy system, which is heavily dependent on fossil fuels, underlies many of the problems we face today: exhaustion of easily accessible physical resources, security of access to fuels, and degradation of health and environmental conditions. Universal access to clean energy services is vital for the poor, and a transition to a low carbon economy will require rapid technological evolution in the efficiency of energy use, environmentally sound low-carbon renewable energy sources and carbon capture and storage. The longer we wait to transition to a low carbon economy the more we are locked into a high carbon energy system with consequent environmental damage to ecological and socio-economic systems, including infrastructure.
  • Emissions of GHG emissions are one of the greatest threats to our future prosperity. World emissions (flows) are currently around 50 billion tonnes of carbon dioxide-equivalent (CO2e) per annum and are growing rapidly. As the terrestrial and oceanic ecosystems are unable to absorb all of the world’s annual emissions, concentrations (stocks) of GHG emissions in the atmosphere have increased, to around 445ppm of CO2e today and increasing at a rate of around 2.5ppm per year. Thus we have a flow-stock problem. Without strong action to reduce emissions, over the course of this century we would likely add at least 300 ppm CO2e, taking concentrations to around 750 ppm CO2e or higher at the end of the century or early in the next. The world’s current commitments to reduce emissions are consistent with at least a 3oC rise (50-50 chance) in temperature: a temperature not seen on the planet for around 3 million years, with serious risks of 5oC rise: a temperature not seen on the planet for around 30 million years. Given there are some uncertainties present in all steps of the scientific chain (flows to stocks to temperatures to climate change and impacts), this is a problem of risk management and public action on a great scale.
  • Biodiversity has essential social, economic, cultural, spiritual and scientific values and it’s protection is hugely important for human survival. The rapid loss of biodiversity, unprecedented in the last 65 million years, is jeopardising the provision of ecosystem services that underpin human well-being. The Millennium Ecosystem Assessment concluded that 15 of the 24 ecosystem services evaluated were in decline, 4 were improving, and 5 were improving in some regions of the world and in decline in other regions. Measures to conserve biodiversity and make a sustainable society possible need to be greatly enhanced and integrated with social, political and economic concerns. There is a need to value biodiversity and ecosystem services and create markets that can appropriate the value for these services as a basis for a ‘green’ economy.
  • There are serious short-comings in the decision making systems at local, national and global levels on which we rely in government, business and society. The rules and institutions for decision making are influenced by vested interests, with each interest having very different access over how decisions are made. Effective change in governance demands action at many levels to establish transparent means for holding those in power to account. At the local level public hearings and social audits can bring the voices of marginalized groups into the forefront. At national level, parliamentary and press oversight are key. Globally, we must find better means to agree and implement measures to achieve collective goals. Governance failures also occur because decisions are being made in sectoral compartments, with environmental, social and economic dimensions addressed by separate, competing structures.
  • Decision makers should learn from ongoing grass-root actions and knowledge in areas such as energy, food, water, natural resources, finance and governance. This is key, not the least in rural communities with a view to their management, control and ownership of these resources. There is a need to scale-up the grass roots actions by bringing together a complementary top-down and bottom-up approach to addressing these issues. Global cooperation can be improved by building on on-going regional cooperation to deal with common sustainable development issues.
  • Effective training programs should be implemented to multiply the number of competent decision makers in business and government. They must learn how to integrate programmes and policies within sustainability constraints, to understand the business case thereof, and acquire the skills to strategically move towards such sustainability goals.
  • All of the problems mentioned above demand we increase investments in education, research and assessments of knowledge.
  • If we are to achieve our dream, the time to act is now, given the inertia in the socio-economic system, and that the adverse effects of climate change and loss of biodiversity cannot be reversed for centuries or are irreversible (for example, species loss). We know enough to act, but the current scientific uncertainties, means that we are facing a problem of risk management on an immense scale. Failure to act will impoverish current and future generations.

Mexican tidal project to tackle fresh water, electricity and marine life sustainability

The Tiburón Agua y Electricidad project in Mexico aims to provide thousands of megawatts of power along with enough fresh water to supply large parts of North Western Mexico and the Southwest US. It also claims it will be home to a reef-growing infrastructure that will keep sea life and fishermen happy.

Tiburón Agua y Electricidad project in Mexico
Tiburón Agua y Electricidad project in Mexico

By Jason Deign

Grab a map of the world and see if you can spot what is arguably the best location on the planet for tidal power. Found the Gulf of California yet? That is where Kenneth D Lampner hopes to build one of the biggest and most self-sustaining tidal projects he thinks the world has ever seen.

Specifically, Lampner, who cut his teeth in the renewable energy industry 30 years ago with Solar Integrations, a PV company he still runs, is looking at a site called Infiernillo Strait, near the Mexican town of Bahia Kino, in Sonora.

The shallow Strait runs between the mainland and Tiburón Island, which partially blocks the Gulf and creates a choke point for incoming and outgoing tides. “What’s different about my project is the location,” Lampner says. “It’s a river in the ocean.”

Under a project being permitted by the Mexican Comisión Federal de Electricidad, Lampner aims to tap the three-metre tidal surge at both ends of the Strait to create an estimated 1,500 to 5,000 MW of power an hour.

This output is expected to be fairly constant as it takes the tide about seven hours to fill the Tiburón basin on the far side of the island, and about five hours to drain from it, besides there being a time lapse between the southern and northern ends of the Strait.

Most of the power will be used to drive the world’s largest desalination plant, a reverse-osmosis facility with a capacity of 350,000 cubic metres per day, to provide water for nearby Hermosillo and the surrounding area, and potentially for export to parched North Western Mexico, Arizona and Southern California.

This would take advantage of a 2003 Mexican self-supply law that allows private projects to generate electricity for their own use. Any leftover energy could potentially be fed into the grid, Lampner says.

Ecosystem protection
And he hopes to achieve all this without damaging the already frail ecosystem of the Gulf, a UNESCO World Heritage Site sometimes referred to as ‘the world’s largest fish trap’ which has nevertheless suffered significantly from overfishing in recent times.

The secret is a novel energy generation method that eschews the use of barriers or ‘spinners’ in favour of a vertical-axis Francis turbine design that exploits the variation in water level caused by the tides.

Lampner’s plan is to have these turbines anchored to the 12-metre seabed in the Strait but located close to the surface, so that marine life beneath them is not affected by their presence, and with channels so that fishermen and seagoing mammals can navigate between them.

The anchoring method he has chosen is as novel as his turbine design. His company, Tiburón Agua y Electricidad, has co-opted Dr Thomas Goreau, president of the Global Coral Reef Alliance, to create an infrastructure using a reef growth technique called Biorock.

With Biorock, a very low voltage current is passed through a wire frame so that minerals precipitate onto it, forming a limestone skeleton that can serve as a home to corals and other marine life.

“These are solid structures that gain strength in time and are self-repairing,” says Goreau. “The purpose is to tap surface tidal currents. We’re not trying to build a barrage, but it’s going to require support structures.”

Goreau says that if Biorock deposition happens at an optimal rate of 1-2 cm per year then “you get a structure that’s two or three times stronger than Portland cement.”

That might not be possible in the Tiburón development, he adds, because of the need to have structures that are strong from the outset.

Long-term benefits
Even if there has to be some compromise on this point, though, the continuously strengthening properties of Biorock should provide long-term benefits, and not just from an infrastructure point of view.

Organisms grow two to six times faster on Biorock than on traditional undersea substrates, Goreau says, “so we should be able to create much lusher fishing grounds.”

Besides Goreau, the Tiburón team counts Dr Chi Lin of Tianhuangping Pump Storage, which worked on the Three Gorges Dam development in China, and a number of engineering and renewable energy specialists. Lin will be responsible for sourcing the turbines from China.

Lampner, who describes himself as “being in real estate”, expects to foot most of the US$1.55bn cost of the project from investments in old goldmines, from which he hopes to extract other valuable minerals, such as silver.

Currently he is hoping to complete a detailed tidal site assessment of the Infiernillo Strait at the time of the spring high tides. But he accepts his grand design is taking time to come to fruition. “Three and a half years ago I thought I’d have it done in two years”, he says.

“I’m trying to push it as fast as I can because I’d like to see it done before I die.”

With a capital cost recovery estimate of five years for electrical generation and desalination, the project could become a viable, long-term and sustainable clean-energy franchise capable of satisfying the rapidly growing demand for water in the State of Sonora.

Fast facts

  • Total estimated project construction cost: US$1.550 billion (tidal electric generators: $750 million; power station: $250m; desalination plant: $350m; aqueduct: $150m; pumping stations: $50m).
  • Proposed electric project capacity: 1,500 to 5,000 MW
  • Proposed desalination plant capacity: 350,000 m3/day

Source: MLA citation: “Tiburon Agua y Electricidad”. Anti Essays. 6 Feb. 2012 <

Long Term Sea Surface Temperatures Trends In Us Affiliated Pacific Islands From Satellite Data, 1982-2003

Thomas J. Goreau, PhD
Raymond L. Hayes, PhD
Global Coral Reef Alliance

Monthly average NOAA satellite-derived Sea Surface Temperature (SST) values from 1982-2003 and their long term trends are presented for sixteen US affiliated Pacific Islands: Midway, Johnson, Maui, Tutuila, Bikini, Enewetak, Kwajalein, Majuro, Kapingamarangi, Kosrae, Pohnpei, Chuuk, Yap, Palau, Guam, Saipan, and Palmyra from the Global Coral Reef Alliance Long Term Global Coral Reef Sea Surface Temperature Database.

These data were compiled from NOAA data and are part of a worldwide database covering every major reef area of the world. All sites show clear upward trends in mean temperature but these differ from place to place due to regional trends in ocean circulation. Also very noticeable is a strong cooling event in 1982, especially in some northern Hemisphere sites, cause by stratospheric aerosol plume from the eruption of the El Chichon volcano, and a much smaller one at some sites from the Pinatubo eruption in 1991. The upward trends at all sites remain when those years and when El Nino years are removed from the data (for more details see references). The raw data trend equations are shown on each graph where x is time in months.

For much more information on methods, results, and analysis see:
1. T. J. Goreau, R. L. Hayes, J. W. Clark, D. J. Basta, & C. N. Robertson, 1993, Elevated sea surface temperatures correlate with Caribbean coral reef bleaching, p. 225-255 in R. A. Geyer (Ed.), A GLOBAL WARMING FORUM: SCIENTIFIC, ECONOMIC, AND LEGAL OVERVIEW, CRC Press, Boca Raton, Florida.

2. T. J. Goreau, & R. L. Hayes, 1994, Coral bleaching and ocean “hot spots”, AMBIO, 23: 176-180.

3. T. J. Goreau & R. L. Hayes, 1995, A survey of coral reef bleaching in the South Central Pacific during 1994: Report to the International Coral Reef Initiative, 201p. (Book), GLOBAL CORAL REEF ALLIANCE, Chappaqua, New York.

4. T. J. Goreau, R. L. Hayes, & A. C. Strong, 1997, Tracking South Pacific coral reef bleaching by satellite and field observations, PROC. 8TH INTERNATIONAL CORAL REEF SYMPOSIUM 2: 1491-1494

5. T. J. Goreau & R. L. Hayes, 2005, Monitoring and calibrating sea surface temperature anomalies with satellite and in-situ data to study effects of weather extremes and climate changes on coral reefs, WORLD RESOURCE REVIEW, 17: 242-252

6. T.J. Goreau, & R.L. Hayes, 2005, Global coral reef bleaching and sea surface temperature trends from satellite-derived Hotspot analysis, WORLD RESOURCE REVIEW, 17: 254-293

7. T.J. Goreau R.L. Hayes, & D. McAllister, 2005, Regional patterns of sea surface temperature rise: implications for global ocean circulation change and the future of coral reefs and fisheries, WORLD RESOURCE REVIEW, 17: 350-374

Questions and answers about Biorock installations

1) What is the cost of installing a structure of 10 m2 width x 5 mt2 height?

I guess you mean 10m x 10m x 5 m, or 100 square meters? A very rough estimate would be $10,000 including travel, time, and expenses for our team. Compare the cost of house the same dimensions. Of course this is highly dependent on the actual design of the structure, the amount of materials and electricity needed, power source used (solar panels would make it more expensive!), depth, distance from shore, and wave energy at the site.

2) Is it necessary to transplant corals to the structure, or would they also group the structure because of they proximity to a natural reef?

We get record growth rates of corals, and also record rates of baby coral settlement, but not under the same conditions. When we grow quickly to maximize structural strength (as is needed where there is high wave energy) then the millimeter sized baby corals are overgrown by the minerals. We can reduce the power later and get very high settlement, but normally we transplant naturally broken corals (which would otherwise die) and grow them very rapidly for the fastest results.

3) What is the death rate of transplanted corals?

We don’t have good numbers on this. There is some mortality to be sure, because of diseases, storm damage, tourists, and in the Pacific where many coral species are genetically programmed to die when they reach a certain size, but the mortality is much less than transplantation to artificial substrates like cement, because our corals have much higher survival under high temperatures, sedimentation, and nutrients.

4) How long does a coral take to get attach to the structure, and how long does the structure take to adhere to the ocean floor?

We see corals start to overgrow the limestone substrate within a day, they are usually firmly attached within a week. The structures will cement themselves to hard rock bottom on the same time scale, being more firmly attached with time. A few days ago I got a report that some of our seagrass restoration projects in southern Italy (Mediterranean) were so solidly “welded” on to the rock they could not remove them.

5) What kind of species can be transplanted, and which not (Does the ocean depth have any impact on these)?

All species of corals, both hard and soft do well, but some do much better than others. Very fragile corals can grow fast but tend to break. A few species respond less well than others, for reasons we don’t yet understand, but most grow at record rates. We can work at any depth, in Sweden we are growing deep cold water corals in the lab, and could grow them using Remotely Operated Vehicles for maintenance on deep oil rigs, for example. Wolf Hilbertz got mineral growth at a depth of I think around 5,000 meters in the Cayman Trench. But to be effective shore protection structures will come near to the water surface, and for snorkeling reefs I prefer around 5 meters depth, shallow enough for tourists to see but deep enough that they can’t damage them (most can’t swim very well, and can damage anything they can kick). Deeper structures for divers are no problem but require much more diving time, as one uses air quickly while doing hard physical work.

6) How often should the structures be visited, and what kind of special care they demand?

Simple visual observations or photographs can tell us if it is working. Maintenance mainly involves pulling off algae or sponges that might overgrow coral, and any coral eating animals, like fireworms (gusano de fuego) or certain snails. The main cause of problems are electrical cables broken by hurricanes, but these can be easily repaired. Where shore transformers are used, erratic power can burn them out. For serious repairs Gabriel will be close by, and we would plan to train local partners for routine maintenance.

7) What is the most suitable system to provide energy for the coral structure?

This is very site specific. We have used transformers to power projects where there is electricity at the shore, but we are now building our own proprietary power supplies that are more efficient, allowing larger projects to be built further away. We have done many solar projects (but this is the most expensive option unless there is no alternative), and wind powered projects. Much of our focus now lies in using ocean currents and wave energy to make power on site, but the first is very site specific.

8) What is the estimated energy consumption of structure?

That depends on the amount of steel and how fast one wants it to grow, but we often grow structures say 6-7 meters in diameter using around 30-50 watts, or like a dim light bulb. Large structures, say 20 m across, will use a few hundred watts, like a bright light bulb. We can grow a reef the whole length of a beach for around as much electricity as the shore lights, or a couple of air conditioners worth of electricity.

9) How much does the maintenance of the structure costs per year?

We don’t have really good figures for this. The electricity is equivalent to a very small part of what any hotel spends on lighting or air conditioners. If there is serious damage and we need to come and replace cables or power supplies that of course costs more.

10) What kind of training does a diver need to install this kind of systems?

Special training is needed, because although the concepts are simple and easily taught, they have to be done right, and that takes experience and hands-on training. The craft of workmanship is as important as the concepts. That is why we are about to hold the 7th Indonesian Biorock Training Workshop. We have not yet held one in the Caribbean, but we typically train our local partners when we install a project. Not all pay enough attention to do it all themselves without a little help the first time, but those who are really motivated do.

11) Is there any specific layout or accommodation for the corals to optimize the growth? What’s the optimum spacing between each coral? Or should it be together?

The more corals the faster the fishes come to it. But we rarely have enough time to transplant as much coral as we would like. In some cases dedicated local partners have completely covered them with corals, with excellent results, but that is a lot of work. We try to maximize diversity and grow quick growing corals that we can propagate.

12) What are the specs of the structure? Material soldering procedure? And what are the best ways to transport it to the installation place?

Best is to weld the structure on land, but we have made many structures simply tied together with wire. However that is not as good if there is heavy wave surge, as the structure is weakest at first and gets stronger with time. We usually float the structure to the site by carrying and swimming it to the site or towing it by boat or on board the boat.

Suitability of mineral accretion as a rehabilitation method for cold-water coral reefs

Journal of Experimental Marine Biology and Ecology, Susanna M. Strömberg a, Tomas Lundälv b, Thomas J. Goreau c, August, 2010

An example of images taken at the start (left) and at the end (right) of the experiment. Measurements were performed in the free software ImageJ (version 1.42a). This particular coral piece was reared in the lowest applied current density (LI: 2.0V, ≤0.06 A m-2). A new bud has developed from a small protrusion into a long calice, and the upper left calice (numbered 4, 5) has grown noticeable.

Download PDF

AMLC/ALMC, Association of Marine Laboratories of the Caribbean Asociación de Laboratorios Marinos del Caribe

Proceedings of the 34th Scientific Meeting of the Memorias de la 34va Reunión Científica de la Center for Sponsored Coastal Ocean Research, Caribbean Fisheries Council Institute for Tropical Marine Ecology Inc. May 25-29, 2009.

Download paper: AMLC/ALMC, Association of Marine Laboratories of the Caribbean Asociación de Laboratorios Marinos del Caribe