1. Introduction

Coral reefs rank among the largest and oldest living communities of plants and animals on Earth. These soft-bodied invertebrates that make reefs evolved 200-450 million years ago. Most established coral reefs began growing 5000-10,000 years ago (Hinrichsen, 1997). Coral reefs play an important role in ensuring sustainability in the oceans. For example, coral reefs recycle nutrients from mangrove swamps and seagrass beds, for open-ocean fisheries that provide food for people (Ibid.). Reef plants and animals also produce many chemicals for potential use in pharmaceuticals (Ibid). Additionally, coral reefs attract tourists, boosting the economy of the country. However, the environment of the coral reefs is not favourable for them to grow. Since seawater temperature is rising due to global warming, coral bleaching will become more widespread and severe, affecting the coral reef community structure (Ogden, 1998). When seawater temperature rises, zooxanthellae, a kind of algae living in corals, stop photosynthesising and produces toxins, causing the coral to release it (Castro, 2013). Unlawful acts such as dynamite fishing are still carried out in many places around the world. For example, over-harvesting, cyanide poisoning and bombing by cash-poor fishermen, and then a massive bleaching event in 1998, had virtually destroyed the marine garden of Pemuteran (Porteous, 2009).


Biorock™ is a trademark used by Biorock, Inc, which is the deposit product of immersing galvanised iron mesh cathodes and iron/lead anodes in seawater for the accretion of minerals (Hilbertz, 1979). Biorock™ was one of the only coral reef ecosystem rehabilitation methods since the late 1900s, developed by Thomas Goreau, a marine biologist and Wolf Hilbertz, an engineer (Ibid.; Bachatiar, 2003). Mineral accretion process involves applying a low voltage direct electrical current through electrodes causing mineral crystal naturally found in seawater, mainly calcium carbonate and magnesium hydroxide to form on the structure (Ibid.; Hartt 1984). An experiment was conducted in which water/sand mixtures were kept at a temperature ranging from 78 to 82°F/26°C to 28°C (Ibid.). Power was supplied for 720 h at a rate of 5 V, 300 mA (Ibid). During the experiments, fresh sea water was added at intervals to replace water lost through evaporation and electrolysis (Ibid.). The experiment produced CaC03/Mg (OH). 2 formations (Ibid.). Many similar experiments were conducted, although the conditions were altered slightly. For example, an experiment was devised to accrete on a 15 cm by 15 cm 1/2’’ galvanised hardware cloth cathode with a 1 mm × 15 mm × 30 mm lead anode at a depth of 450’ at Cane Bay, St. Croix, for 42 h (Ibid.). The current was supplied by a car battery and measured 12.25 V/1.65 At the beginning of the experiment, and 3.8 V/170 mA at the termination (Ibid.). It has also been found out that different setups of the Biorock™ method has different results: supplying power would result in more fauna, while not supplying any power would result in more flora (Ibid.).

It has also been discovered how electrodeposited minerals can be used as building materials in the construction of artificial reefs, which relieves pressure on natural reefs (Ibid.). The wire mesh does not corrode since the initial layer of electrodeposited material and the constant flow of electricity protects it (Ibid). The shell, which resembles limestone and is mainly compounds of calcium carbonate and magnesium hydroxide, is lighter and stronger than reinforced concrete, able to withstand pressure exceeding 4200 pounds per square inch (Ibid.). This is equivalent to a load-bearing strength of up to 80 newtons per square millimetre (80 megapascals). , around three times higher than concrete made from ordinary Portland cement (Goreau, 2010). This process can also be used on a large scale to grow homes, ships, pipelines, piers, structural members for larger buildings, and artificial islands (Hilbertz, 1987). Biorock™ electrolysis of seawater has been used for nearly 35 years in more than 20 countries to grow limestone structures of any size and shape in seawater and brackish water, for example, it is suggested that the Biorock™ technology might be supporting Venice’s sinking foundations all this while (Goreau, 2010). Another example is the water in front of the village of Pemuteran, North Bali. The Pemuteran Biorock Project started in the year 2000, when the Karang Lestari Foundation was formed (Ricciardi, 2014). Their aim was to rebuild the local coral reefs that have been bombed (Ibid.). Only a few years after the first structure was installed, the results came quickly (Ibid.). The corals grow quickly and are healthy, and fish life is abundant (Ibid.). Invertebrates like crabs, sea slugs and shrimp are abundant and now occupy every shelter inside the Biorock™ (Ibid.). Also, the base of the Biorock™ can be placed in whatever shape you choose so it can be an artistic way of regrowing corals (Ibid.). The Biorock™ structures can thus be a kind of a tourist attraction (Ibid.). Also, hotel and dive shops can be grown nearby reefs as beautiful tourism attractions that can restore nearby fisheries and reduce pressure on natural reefs (Goreau, 2003; Hilbertz 2003). Thus, increasing the revenue generated by tourists visiting these structures, most probably even higher than with natural coral reefs. Now, the Karang Lestari Foundation is carrying out a Biorock™ project similar to the one carried out in Pemuteran. Another Biorock™ project had been carried out in Gili Trawangan, one of three small islands north-west of Lombok in the Indonesian archipelago (Silver, 2015). Similarly, a tourism industry has sprung up there due to this project (Ibid.). Apart from building, Biorock™ can also be used to increase the rate of oyster and coral growth (Goreau, Hilbertz, Azeez, Hakeem, & Allen, 2003). It directly provides energy for growth of skeleton and shells, so it leaves corals and leaves corals and oysters more energy for growth, reproduction and resisting environmental stress (Ibid.). Field experiments in all oceans show that electrified corals and oysters grow faster and survive better. Large populations of adult and larval fishes are also quickly built up (Ibid.). Electric reefs can be constructed in any size or shape, allowing selective enhancement of selected fish and shellfish populations (Ibid.).

However, this setup is not invincible. There were some severe hurricanes that happened in the Grand Turk, Turks and Caicos Islands (Wells, L., Perez, F., Hibbert, M., Clerveaux, L., Johnson, J., & Goreau, T., 2010). After hurricanes Hanna and Ike (September 2008). The Governor's Beach structure was fully standing since the waves passed straight through with little damage, but the Oasis structures which were tie-wired rather than welded had one module collapse (Ibid.). Hurricane Ike was the strongest hurricane on record to hit Grand Turk (Ibid.). Most cables were replaced following the hurricanes due to damage from debris and high wave action. The projects lost about a third of the corals due to hurricanes (Ibid.). Most of those lost had only been wired a few days before and had not yet attached themselves firmly (Ibid.).

Restoration of ecosystems and fisheries will be a major challenge of the coming century as increasing population and energy use cause global climate change and environmental degradation to accelerate (Goreau, 2003; Hilbertz 2003). Therefore, we could support such organisations carrying out projects, such as Biorock, to save our dying ecosystem.



1.2 Problems Being Addressed

A widespread issue around the world is coral bleaching. Corals are marine invertebrate that thrive in coral reefs, which are built and held together through corals secreting calcium carbonate. Coral reefs are extremely important to various groups of people or animals. Firstly, coral reefs are habitats to approximately 5 billion fishes. Therefore, a large percentage of fishing yields can be attributed mainly to coral reefs. Based on research, an estimated one billion people have some dependence on coral reefs, either for food or income from fishing. If properly managed by the fisheries and private fishermen, along with other companies that interact with the ocean. , reefs can yield around 15 tonnes of fish and other seafood per square kilometre each year. Secondly, tourism can generate a huge amount of income for a country, as people may travel far and wide just to catch a glimpse of a coral reef, like the Great Barrier Reef. According to a report by the Key West chamber of commerce, tourists visiting the Florida Keys in the US, coral cay archipelago, generate at least US$3 billion dollars in annual income from tourism alone, which is mainly contributed to by coral reefs, while Australia’s Great Barrier Reef, the largest coral reef ecosystem, generates well over US$1 billion per year. Therefore, sustainable management of coral reef ecosystems and proper tourism measures can significantly increase a country’s income and GDP. Another way that coral reefs can contribute is through protecting coastal areas from natural disasters such as tsunamis, typhoons, hurricanes and the like. This helps to prevent coastal erosion (which leads to water pollution). , and damage or loss of property on or near the shoreline, which can cause millions or even billions of dollars of damage in terms of reduced insurance and reconstruction costs, as well as costly coastal protection defences. Fourth is the obvious reason of coral reef organisms being used for medical purposes, like in tropical rainforests. Currently, there are already coral reef organisms used to treat cancer and HIV. Thus, if the coral reefs are taken care of and are health, Last of all, the coral reefs are interwoven with the culture and social fabric of many places. For some people who have experienced snorkelling with a mask and snorkel, looking at the colourful corals, a life without corals is no life at all.

1.3 Engineering Goals
We are aiming to develop a sustainable system which is able to rebuild the habitat suitable for coral growth. Through this, we hope to aid in the coral regeneration around the world and reduce the effect of global warming on the population of corals.

1.4 Specific Requirements
  • We want to develop a system, which is able to recreate a sustainable coral habitat.
  • Control the population (mass) of the coral based on the amount of deposit.
  • Control the temperature of the water using the cooler system.
  • Collect energy using solar panels and store the energy in a rechargeable battery, where the energy stored will be used in case of lack of sunlight (e.g. at Night).


1.5 Alternative Solutions
1.5.1 Design 1


Our first design shows all the items connected to the solar panel. The whole setup makes use of the electricity from a solar panel, thus too much power is needed. However, in the open ocean, there is no need for coolers and water pumps, as the water temperature will be okay and there will be sufficient oxygen from aquatic plants.



1.5.2 Design 2
Our second design is similar to the first design, except the anode and cathode are connected to a battery and circuit regulator, which is in turn connected to a solar panel for an electrical supply, which is how it will be like on the open ocean, as there is no other electrical source to power the anode and cathode. However, the cooler will still be connected to an electrical plug as in the open ocean, the water is naturally cool. Therefore it will not be used in the actual open ocean setup. This will only be carried out after design 3 has been utilised to test if the setup works.




1.5.3 Design 3


Our third design consists of a copper rod (anode) and wire mesh (cathode) and a cooler, all of which is connected to an electrical plug. This setup is used to test whether our setup really works, without the possible errors that could surface due to the solar panel (e.g. solar panel not functioning). Despite the fact the Solution 3 obtained the highest number of points, we cannot use that solution because all the electricity is obtained from a power point. This is impossible in the open ocean, but due to its ease of use, it obtained a very high point.




1.5.4 Ocean Context
This is the closest to what will actually be used on the open ocean. It is quite different from the first two designs. First of all, the anode and cathode are still connected to the circuit regulator, battery and solar panel, but the cooler is missing as the temperature in the ocean is cool enough. The circuit regulator, battery and solar panel are placed on a large floating platform, and a large copper rod (anode) and wire mesh (cathode) is allowed to sink to the bottom of the ocean, connected by an extremely long wire. On top of the floating platform is a shelter to prevent short circuit caused by rainwater.



1.5.5 Ranking Matrix

Colour
Weight
Size
Cost to produce
Elegance
Robustness
Aesthetics
Resources
Time
Skill required
Safety
Ease of use
Environmental Impact
Row Total
Normalised value
Colour

0
0
0
0
0
0
0
0
0
0
0
0
0
0
Weight
3

0
3
3
0
3
3
0
0
0
0
2
17
0.07
Size
3
0

3
3
0
3
3
0
0
0
0
2
17
0.07
Cost to produce
0
0
0

0
0
0
0
0
0
0
0
0
0
0
Elegance
3
3
3
3

0
3
3
0
0
0
0
0
18
0.08
Robustness
3
3
3
3
3

3
3
0
0
0
2
3
26
0.11
Aesthetics
3
0
0
2
0
0

1
0
0
0
0
0
6
0.03
Resources
3
0
0
3
1
0
2

0
0
0
0
0
9
0.04
Time
3
3
2
3
3
2
3
2

2
2
2
2
29
0.12
Skill Required
3
3
3
3
3
1
3
2
0

1
1
1
24
0.10
Safety
3
3
3
3
3
3
3
3
1
2

2
3
32
0.14
Ease of use
3
3
2
3
3
3
3
3
2
2
3

3
33
0.14
Environmental Impact
3
2
1
3
3
3
3
3
0
1
0
2

24
0.10













Total
235





1.5.6 Decision Making Matrix
Requirement

Solution 1
Solution 2
Solution 3
Factors
Normalised value
Votes (0 to 5).
Normalised votes
Votes (0 to 5).
Normalised votes
Votes (0 to 5).
Normalised votes
#1: Ease of use
0.14
4
0.56
4.33
0.60
5
0.70
#2: Safety
0.14
1
0.14
1.67
0.23
3
0.42
#3: Time
0.12
0.67
0.08
1
0.12
1
0.12




1.5.7 Best Solution & Rationale

After selecting ease of use (as people will only make use of it if it is easy to setup and maintain), safety (since we are dealing with electricity and water, safety is of the utmost importance) and time (if it takes forever to set up, the impact on the environment will be significantly increased). We then came to a conclusion of that the set-up that we will be using would be Solution 2, even though the set-up with the highest votes is Solution 3.


Reason for voting time badly: This is because Biorock is a very long process which takes years to collect a bit of rock. With such a short time frame we are given, we are just simply planning to cultivate just a small portion of biorock, enough that we are able to prove that our experiments is able to sustain throughout the day.

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