Our second attempt used galvanised steel sticks built into the blocks. Coral fragments were attached to the sticks by cable ties. This method of attachment is much easier to accomplish and the corals did well the mortality rate of the fragments dropped significantly. The drawbacks were the cost of the material: cement and galvanized steel; and effort required to place the blocks.
To expand the value of the already placed blocks, we stacked them up to create fish houses. With this process we we achieved two aims: there were elevated structures added to the rubble areas, which provided a fish retreat and protection. The process also lifted the small coral fragments higher up in the water column.
By October 2007, the central and northern house reef sections had been completed and 50 concrete block structures of different shapes have been transplanted with coral fragments. The concrete structures began to attract a number of benthic species, which started to colonize the blocks. All the structures started to closely blend to the surrounding environment. Many juvenile fish found a refuge under the structures and nudibranches seem to favor the concrete as an ideal substrate on which to mate and to lay their eggs.
There are many options for creating structrures or substrates for an artificial reef; key considerations include eco-friendliness, effectiveness, cost and aesthetic impact.
Starting in April 2007, we also have installed three BioRock©s. The Tunnel was placed out in April, The Blob in December and finally The Pagoda was installed in February 2008. Biorock is a metal structure through which low electricity current is fed to promote calcium carbonate deposition. Calcium carbonate, coral building material, enhances the growth rate of corals and other sessile organisms that attach to this structure. Most of the transplanted corals branching, massives and plates are doing well and we have seen an increase of growth from the original colonies. So far the Biorock shows very high survival of coral colonies and starts to attract further benthic settlement.
Another addition to the house reef project was the sinking of a 15 meter wooden boat onto the deeper part of the reef. It sits on the sandy bottom in about 24 meters of water.
The wreck was sunk in December 2007 and it was purposely sunk quite deep, to attract marine life to the deeper part of the house reef, in particular some of the large predatory fish species that previously inhabited the area. Since the house reef hasnt been fished since the resort opened in 2003, the wreck serves as a refuge for sought after market fish (cods, snappers, sweetlips). Again this support system for these type of fish can be expanded by sinking bigger wooden boat along the sandy slope.
We also have placed two squid ropes on either side of the wreck and laid down ropes along the slope. Squid ropes attract squid lying eggs. Ropes on the sand are there to attract critters like frogfish, seahorses or tozeuma shrimps, which seek shelter on ropes.
Biorock is basically a growing, living metal structure underwater through which low- voltage electricity is distributed. The electric field surrounding the metal structure promotes CaCO3 (limestone) growth on the metal, and with time the structure grows larger and larger, the same way that coral grows.
In order to construct a Biorock, you will need material for the BioRock© itself, most preferably the cheapest (not galvanized) metal bars or rebar. There is no need to use expensive metal. In any case do not use aluminium for any part of the structure as it will dissolve.
Secondly, you will need anode, to which the positive current is led. Anode on the other hand cannot be any other metal than titanium. Titanium mesh (quite costly, $50/m2) will not dissolve, as lead or steel will. It is permanent, will last for years and years and it is non-toxic.
Third, you need a cables, triple isolated, 2.5mm2 cable. We had You to buy these in Mandao. We connected the cables is one whole cables (negative, positive and ground) one attaches as negative and one as positive source.
You will need epoxy marine glue to connect the cables to the anode and to the structure. Also you will need to make a connection in the cables if they do not reach all the way to the Biorock. Obviously, the fewer connections you make, the lower the chance of error, so try to use as long cables as possible or and place the Biorock close enough to the shore.
The way the Biorock works is relatively simple. Seawater creates an electric field. By placing the anodes on either side of the BioRock, you will create even limestone deposition. The size of the anode should be about 1/20 of the size of the structure, but this is only educated guess, there are no strict rules.
Distance from the shore is a limit. If using a battery charger, the DC current running through is only effective for about 100m, assuming you are using at least 2.5mm2 thickness cables. Anything further away from shore, solar panels should be used. If you could use an underwater AC/DC converter, the distance would be no limit. In areas suitable for that tidal or wind power can be used.
Bio Rock Bulb
Transplanting coral at Bio Rock tunnel
BENEFITS OF THE BIOROCK
There is some discussion about the effectiveness of the BioRock but here is the list Tom Goreau (www.globalcoral.org ), one of the creators of the method, highlights:
Corals transplanted onto the structure show 3-5 times faster growth
* There is up to 20 times faster healing process of corals, indicated by lesser or no mucus secretion
* 16-20 times better survival in elevated sea temperatures (this is based on BioRocks built in the Maldives before the mass bleaching in 1998)
* Higher settlement of coral larvae
* Fish attractors
From our personal experience: the BioRock is an ideal method to create an extra habitual structure to an area. Coral transplanted onto it does grow and the mortality is very low, compared to other methods of transplanting corals onto fish houses. We also try to choose corals laying loose in the substrate or colonies partly attacked by a predator (coral eating sponge); generally we pick corals that are likely to die if left in their original state, or place. Elevating the corals gives them better position to photosynthesize and we assume they have a better chance to survive and to grow. Fish are naturally attracted to structures for protection and the Biorock is no exception.
If you take a coral colony attacked by the coral eating sponge break of the healthy part of the colony and make sure none of the sponge is left.
OTHER HOUSE REEF PROJECT
Board Cuttlefish at Reef Balls
There are currently 20 Reef Balls that are separated into two groups, situated north of the Biorocks. These reef balls are all hollow spheres with a large hole on the top and several around the sides to increase structural complexity. All balls are approximately one meter in diameter. They are made with coarse grain cement which is a good substrate for the successful settlement of coral larvae. One set consists of 8 balls in about 16-17.5 meters. The second set is approximately 20 meters north of the first and consists of 10 balls in about 17.5-19 meters. There are also several independent balls randomly scattered over this part of the reef.
There are 23 fish house structures that are scattered over a large area from within the Biorock Dome northwards to the Mandarin Fish Dive Site. They are situated in approximately 7 to 15 meters depth and for the sake of the project have been divided into two groups; deep (below 12m) and shallow (above 12m). They were first installed in April- June 2005. Each structure is made out of several long rectangular blocks stacked on top of each other so that they look like a chimney with gaps in the sides. Some of the structures are falling over while others appear very sturdy. There is evidence of some coral settling despite the high sediment cover over most of the structures. Some corals have established themselves and are growing healthily. The Fish houses were perhaps the most successful artificial structure on the house reef. Although they have had a longer period to develop recruitment.
Fish Nets combine with broken washing machine
Transplanting Sponge at Fish Net
Fish Nets combine with broken washing machine
Four washing machines (cleaned of all potential harmful contaminants) were encased in concrete and installed on the house reef in July of 2009 at ~17m, between the Biorocks and the wreck. Between the washing machines, a series of ropes were crossed over each other forming a net like matrix (hence the name fishnet). Approximately 25 sponge fragments were attached to this structure to attempt to increase the number of inhabitants of the area. The Fish Net has been successful in substantially increasing species diversity, the number of individuals and families per cubic meter.
Washing Machine Board Cuttlefish At Fish Net
Concrete Blocks combine with Fish Net
Nudibranch at concrete Blocks combine with Fish Net
Seven slabs of concrete with various “decorative” attachments were lowered down onto the Lembeh Resort house reef in October 2009. Six of these structures are clustered together just north of the fishnet at approximately 22 meters depth, while the seventh was dropped a little deeper at ~25 meters 20 meters from the larger cluster. They are composed of heavy slabs of concrete with various household objects embedded, from a computer and printer to a cooking strainer.
Update: research on the concrete blocks has shown little success in recruitment, with populations and individual numbers remaining constant or in decline.
Reef Octopus at Durm Ladder
The drum ladder was installed in July 2010, with volunteer Madison Bromell (North Seattle Community College). Two cleaned and perforated oil drums were set and secured in place between the fish nets at roughly 75 feet/23 meters. A ladder constructed out of PVC piping connects the two drums in the middle and has colored stones of green and red hanging in several rows along each rung. Most sponges and soft corals transplanted on the drum ladder were gathered within a fifteen foot depth range of the structure, to reduce stress incurred by acclimation. After the first day little fish activity was observed; only the already present Grubfish and a few passing Angelfish and Tobies showed any interest in the structure.
Moderate sedimentation began to accumulate on the structure soon after installation. One week later, self-seeded tunicates including Oxycorynia fascicularis began to attach themselves to the walls of the drums and fish populations continued to increase with additional sets of sponge and soft coral transplants. Soapfish, Angelfish, and Butterflyfish repeatedly came and went, inspecting and grazing on newly transplanted sponges, however Blennies, Grubfishes, and Tobies were found most consistently living in or around the structure. Sponges attached to the ropes and rungs of the ladder were favored by Blennies and Grubfish, and chimney sponges were popular with foragers. Through continued transplanting a large number of large sponges were moved onto the drum ladder in stages, ranging from two to four feet in length. The largest was secured to the drum first, and within the fifteen minutes it took to bring back the next load of transplants, that sponge was already being feverishly picked over by several Butterflyfish, Angelfish and Soapfish. Also on that day, a small Wonderpus was found out in the open not ten feet from the structure. On 3 August, one large Reef Octopus was found sitting on top of one of the drums. The location of the drum ladder poses some interesting ecological questions. It is situated on the edge of three different environments, making it an edge habitat; pelagic, sandy bottom and coral reef.
Reef Builder blocks
Reef Builder blocks
Reef Builder blocks made of concrete and bamboo
In May and June 2011, volunteer/researcher Margaret Thompson (University of Toronto), with the assistance of Dimpy Jacobs and the crew at Critters@Lembeh built 20 blocks made of concrete, sand and bamboo, in a project to briefly measure recruitment and succession on artificial reef structures.
Blocks were assembled in groups of four, and transplanted with
A) soft coral
B) mixture of soft and hard coral
C) hard coral
control, upon which nothing was transplanted
3 groups of blocks were placed on the house reef: 2 at 20 meters and one at ten meters. In addition, two groups were placed at Pintu Colada 2 (a neighboring dive site): one at 10 and one at 20 meters. Recruitment of sessile invertebrates such as tunicates and sea squirts, porifera (white sponge), and macroalgae, motile invertebrates including colonies of periclimenes sp., peacock mantis shrimp, nudibranchs, flatworms, starfish including linkia and fromia, and crinoid feather stars. Vertebrate recruitment has been especially successful for juvenile fish, including banded and network pipefish, glassfish, and cardinal fish, juvenile and postlarval fish that were not successfully identified, and adult sand perch, lizard fish, various species of damselfish, dottybacks, fang blennies, butterfly fish, parrot fish, juvenile yellow margin triggerfish, etc. Secondary recruitment includes surgeonfish foraging on algae covering several of the blocks, and another recruitment was found; an ornate ghost pipefish was at the crinoid that attached on a branching coral that been transplanted to the blocks. So the project is successful.
HOUSE REEF RESTORATION PROJECT