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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.