Fierce and secretive, a moray eel has found shelter in the hollow of a concrete module, deliberately sunk in order to restore the coral reefs of the Larvotto Marine Reserve (Monaco, Mediterranean Sea).

Creating A Reef

Artificial reefs are man-made structures that are either deliberately or unintentio-nally submerged underwater, commonly with the result of mimicking some charac-teristics of a natural reef. They may be created from a variety ofsources and materials including the inten-tional sinking of ships and barges, concrete structures, tyres and other materials.The intentional deployment of artificial reefs enhances the production of reef associa-ted species and mitigates against losses from overfishing, pollution and habitat destruction. Artificial reefs may also be created through unintentional means (e.g., ship or plane wrecks that can become historical in nature) and through structures built for other purposes (e.g., decommissioned oil and gas platforms, jetties, bridges, off-shore lighthouses, etc.

marine life and encourage populations of marine plants, invertebrates and fish.

[Right] The concrete modules provide-luxury appartments for species such as scorpionfish. Nestled between the bricks, where they find the smaller fish and crus-taceans on which they feed, these two are perfectly caomouflaged.

Artificial reefs at the Larvotto Marine Re-serve, Monaco, Mediterranean.For almost 40 years, the Monaco Associa-tion for the Protection of Nature (AMPN) has been involved in many activities desi-gned to protect the marine environment, such as conserving Posidonia eel-grass, reintroducing speces and sinking artificial reefs. The structures provide habitats for

In 2009 the MUSA Cancun Underwater Museum in Mexico was opened with a dual purpose: to serve as a tourist attrac-tion and to help preserve Mexico’s natu-ral reefs, which had become damage by storms, boat anchors and tourism.The museum, completed in 2013, now has a total of 500 sculptures by six artists, in-cluding a large collection of human statues by British sculptor Jason deCaires Taylor.

Each statue is made with PH-neutral ce-ment so that coral, seaweed, and algae are able to grow and develop more easily than they would on other artificial reef structures, such as sunken ships.The statues also feature holes in them, which allow marine wildlife to colonize and feed off the coral.In time, all statues will be covered and the figures barely visible.

The passage of El Nino in 1998 caused the bleaching and mass die-off of corals around El Nido on the island of Palawan, a top tourist diving and fishing destination in the Philippines. WWF-Philippines has been working with numerous partners to install ceramic corals (EcoReefs®) ideally suited for relatively rapid colonisation by corals and other invertebrates (within 7-15 years).

Once it finds a structure to which it can cling, coral can start to develop quickly, as on these old tyres, deliberately sunk in Komodo National Park, Indonesia.

The irregular surface of these concrete spheres encourages the growth of corals and algae. After more than 10 years in the North Sulawesi Sea, Indonesia, they are almost completely colonised.

Spheres of concrete submerged in order to restore a reef that has been destroyed by dynamite, a destructive fishing practice in Misool, Raja Ampat, Indonesia.

Scientists Julian Caley and Shawn Smith have collaborated for 4 years on a huge census of the species of the Great Barrier Reef, led by the Australian Oceanographic Institute and the Great Barrier Reef Foun-dation, and have installed this small arti-ficial reef in order to find out which life forms will arrive to inhabit it.

Artificial reefs are generally installed in regions where there is only sand or a flat sea bed, as seen here on Lizard Island, Queensland, Australia. The introduction of a very complex habitat, with hard founda-tions, has a big impact on local biodiver-sity, both for fixed fauna and flora and for mobile fauna (crustaceans and fish).

Busselton, a small resort town on the south coast of Western Australia, has the longest wooden jetty in the southern hemisphere, at around 2km. At the end of this, a ladder allows one to descend 8 metres beneath the surface of the sea to admire the unde-rwater fauna and flora and the numerous corals which have attached themselves to

the wooden poles.Created 10 years ago, this observatory is today one of most famous artifical reef sites in Australia. More than 300 marine species have been found here, such as leatherjackets (below), moonlighter fish (top right) and shoals of yellow-tailed scad (bottom right).

When the water current encounters a ver-tical structure at the right depth, a zone rich in plankton can be created, providing the primary food source for corals, inver-tebrates and small fish, which in turn at-tracts larger, predatory species.

The establishment of an artificial structure can influence the surrounding underwaterecosystem by locally concentrating food resources, provide habitat and spawning sites for a variety of marine life, and al-tering current flows to create sheltered areas.

In the last years of WWII, German U-Boats prowled the East Coast of the United States, looking to sink merchant ves-sels shipping war supplies. More than 50 wrecks now line North Carolina’s coast, an area known as the ‘graveyard of the Atlan-tic’. Famous for world-class wreck diving, North Carolina has also gained recognition as North America’s premier shark diving destination. The wreck of the Aeolus, deli-berately sunk in 1988 as part of an artificial reef program, is one of many sites where sand tiger sharks congregate year-round.

Shipwrecks, either deliberately or unin-tentionally submerged underwater, make for very interesting artificial reefs. Popular as diving destinations, they can generate economic benefits for coastal communi-ties; durable at certain depths, they pro-vide a surface for colonisation by colour-ful corals, sponges and anemones, which in turns attracts other marine life, such as fish and turtles.

Yellow sponges (Aplysina caverni-cola) on Brioni Steamship wreck, Vis Island, Croatia, Adriatic Sea, Mediterranean

Scuba diver and great rockfish (Scorpaena scrofa) on Brioni Steamship wreck Croatia.

Diver looking at Jewel Ane-mones (Corynactis australis) on the wreck of HMNZS Can-terbury, New Zealand.

The intentional deployment of artificial reefs enhances the production of reef associated species and mitigates their losses from overfishing, pollution and habitat destruction. The wrecks of the Nasi Yalodina in Fiji [left] and the Shakem in Grenada [below] both sank in 2001 and are now well-colo-nised with coral species. Both are popular diving destinations.

Large boats with robust hulls can remain for decades on the ocean bed. On 3rd November 2007, the New Zealand government decommissioned a frigate of the royal navy, HMNZS Canterbury, and sunk it in the Bay of Islands to make an artificial reef. Within a few years, animal and plant life took possession of the 113 metre long wreck, which has now become one of the world’s most beautiful dive sites. This image shows jewel anemones (Corynactis haddoni), which have colo-nised the rails.

Whole shoals of fish have invaded the interior of the HMNZS Canterbury. Across a depth of 32 metres, one may see jacks, snappers, john dories or demoiselle fish. These new style reefs provide small fish with shelter from predators.

On each level, open doors allow divers to enter the giant wreck and visit cabins, kitchens and toilets, inhabited by lobsters and conger eels.

The supertanker Amoco Milford Haven, sister ship of the Amoco Cadiz, sank on 11 April 1991 off Arenzano, near Genoa, after an explosion during the transfer of oil from one tank to ano-ther. The wreck was devastated by a huge fire which lasted several days. The Italian authori-ties decided to let the oil burn at sea, in order

to limit damage to the coast. After breaking in two, the forward part of the wreck sank to a depth of around 450m while the stern part went down just off the small port of Arenzano, at a depth of 82m. The wreck is enormous: 50m high, 200m long and 50m wide. Of the 144,000 tons of crude oil still in the ship at the time of

the accident, only 1 to 2% remains trapped in the rear part and it is estimated that 70% bur-ned off during the fire, which lasted 70 hours. It seems that the blaze reached such high tempe-ratures (900 degrees Celsius), that it somehow sterilised the metal structures and materials normally harmful to all living organisms.

The Amoco Milford Haven is the largest wreck in Europe. The enormous poop deck (a deck that forms the roof of a cabin built in the rear) is crowded with shoals of anthias and bogues. Access to explore the wreck, between a depth of 35 and 55 metres, is provided by the lift shaft which runs through all the decks.

Now resting off the Cavalli Islands, the Rainbow Warrior was attacked by the Frech foreign intelligence services, on its way to protest against a planned French nuclear test in 1985. After the Green-peace ship was refloated and deemed irreparable, it was eventually re-sunk in 1987 in Matauri Bay, New Zealand, to become an underwater memorial and dive site.

The Rainbow Warrior lies at a depth of 18-26m. Various parameters come into play in order for a wreck to become a submarine garden: depth, water temperature, cur-rents and the composition of the sea bed. Artificial reefs alter local habitat by pro-viding hard substrate and complex verti-cal relief where typically none previously existed.

Scuba diver exploring the wreck of aeroplane ‘B-24 Liberator’ Vis Island, Croatia, Adriatic Sea, Mediterranean

Diver in the cockpit of a wreck of a WW II Corsair fighter plane off South-East Oahu, Hawaii.

Plane wreck in Kimbe Bay, Papua New Guinea, Indo-pacific

The Giannis D was on a voyage from Croatia to Yemen, transporting timber, when it hit the Sha’ab abu Nuhas reef at full speed on 19th April 1983. The ship was abandoned by its crew in the Gubal Straight, Egypt, an area famous for its many shipwrecks. There, the Giannis remained afloat for about a month and a half, until a storm broke it in two. The 100m long wreck slid down to the base of the reef at a depth between 23 and 27 metres. Scalefin anthias (Pseudanthias squamipinnis) now swim all over the superstructures of the stern, and the wreck is rich in coral formations, which provide food for hawksbill turtles.

SS Thistlegorm was a cargo vessel of the British merchant navy. It was bom-bed on 6 October 1941 by the Ger-mans, on its fourth voyage to Egypt, near Ras Mohammed in the Red Sea. Filled with supplies that were desti-ned for British forces in North Africa, she was carrying landmines, ammuni-tions and weapons, as well as nearly 200 vehicles inside her holds - Bed-ford trucks, armoured cars, Bren-Car-riers, BAS Motorcycles and aircraft, still identifiable over 70 years after the boat sunk.

The Kasi Maru, sunk during the Second World War, is now colonised by corals and anemones. The concept of artificial reefs is very ancient (dating back to the sixteenth century) and was discovered and deve-loped by Japanese fishermen, who noticed that their catches were considerably grea-ter near to wrecks and bamboo structures, which they deliberately sank.

The Kasi Maru was a Japanese cargo ship which sank at a depth of 50m, after a raid in July 1943 at Munda in the Ironbottom Sound (thus named after the many boats and planes which sank there during the Battle of Guadalcanal in 1942). It lies at the southern extremity of the Strait of New Georgia in the Solomon Islands.

Artifical reefs may present a solution to the constant pressures faced by marine resources and the degradation caused by human activities.But scientists are still unclear about whe-ther they increase fish production by pro-viding a habitat that would otherwise not be present, or if they simply attract fish away from natural reefs. As a result, it is widely believed that they do both.

Deployment of artificial reefs containing toxic chemicals could pose a potential risk of contami-nation to the underwater environ-ment, especially in sensitive coas-tal ecosystems. Therefore, prior to deployment, structures such as ships need to be stripped of ha-zardous materials such as heavy metals, petroleum products, paint cans, batteries, plastics, oil, fuel, asbestos, polychlorinated biphenyls (PCBs), iron, lead paint, and anti-fouling paint - a process that may cost millions. Nevertheless, there is a risk that some pollutants might remain.

The responsible creation of artifi-cial reefs might be seen as a win-win scenario for many, often serving the purpose of waste disposal while benefitting the environment and tou-rism industry. Reefs have developed on structures as unexpected as decommissioned subway cars and vintage battle tanks.Over decades, these defunct objects have become encrusted with life, turning human scrap into natural wonders; a testament to the power of the ocean.

Japanese mini-submarine at 50 metres on the wreck of the Sanko Maru, sunk on 16 February 1944, Kavieng, Papua New Guinea.

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