artificial reef

artificial reef, structure built by human beings that serves as a substitute for a natural coral reef or rocky reef. An artificial reef provides a substrate upon which algae, corals and other cnidarians, and other marine organisms can attach themselves. Over time artificial reefs can develop into vibrant habitats for a wide variety of marine organisms.

Humans have created these structures since at least the 19th century to attract fish; however, the construction of large-scale artificial reefs did not take place until the late 20th century. Many materials can be used to construct artificial reefs, including rock, concrete, and steel, along with sunken ships and other vehicles. Some offshore structures, such as oil and gas platforms, lighthouses, and bridges, inadvertently function as artificial reefs (see also petroleum production).

Benefits

Artificial reefs provide many benefits to marine ecosystems as well as to humans. Where natural reefs have been damaged, artificial reefs can assist with ecosystem restoration by providing habitats for marine organisms. Furthermore, artificial reefs help protect coastlines from erosion by acting as breakwaters. Their presence can increase marine biodiversity in areas where natural reefs are scarce, and these organisms contribute to overall nutrient cycling that improves water quality.

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These structures provide additional habitats for fish, and placing them near existing fishing grounds can benefit both the fish and the humans who harvest them. Fish habitats in artificial reefs take fishing pressure off natural reefs by becoming a type of remote refuge, so artificial reefs can help to support more sustainable fishing practices. In addition, local economies can also benefit from the presence of artificial reefs, since they can become new points of interest that can attract divers, snorkelers, fishers, and other tourists (see also tourism).

Hazards

Artificial reefs must be carefully planned, monitored, and maintained. If they are placed improperly or the materials that they are made from are submerged carelessly, they may damage ocean-floor habitats and decrease biodiversity. In some cases artificial reef components can kick up sand and other materials, covering standing reefs with sediment that damages their corals, or they may be positioned in ways that can cause accidents and shipwrecks. Also, sustainable artificial reefs must be created with materials that will not release toxic chemicals or other forms of pollution into the water.

Seeking to draw fishers and tourists, people sometimes illegally dump materials into the ocean to form makeshift artificial reefs, which may harm the environment and lead to poaching. In the United States some who engage in illegal dumping have been arrested by the law enforcement arm of the National Oceanic and Atmospheric Administration (NOAA), which also provides funding to clear these materials from the ocean.

Types of artificial reefs

Just about any durable material can be made into an artificial reef component; however, many of the most common elements are made of concrete or steel. Some of the simplest artificial reefs are made of piles of rock, which can form a relatively complex substrate with small gaps between one rock and another. With more than one million deployed worldwide, reef balls—domed hollow concrete structures that are dotted with holes—are one of the most common artificial reef devices because they mimic the structure of a natural reef. Their holes can be used by fish and invertebrates for ingress and egress. Other concrete reef structures are shaped like pyramids or pipes for the same purpose. In addition collections of oyster shells and rock can help conservationists restore or encourage natural oyster reefs. As part of reef restoration projects, scientists may attach fragments of corals or other organisms to these structures to encourage propagation and better the chances of artificial reef success.

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Other human-made items are sometimes repurposed to form artificial reefs. Metal and concrete piping and wind-turbine supports can be submerged to serve as artificial reefs. Several types of vehicles, including automobiles and subway cars, have been sent to the ocean floor for this purpose. During the late 20th century bundles of tires were used as artificial reefs, but they have since been found to cause water pollution. Shipwrecks often become inadvertent artificial reefs, and old boats, ships, and barges have also been purposely scuttled for this purpose. For example, Tangalooma Wrecks is an artificial reef made of 15 scuttled ships that form a harbor off Moreton Island in Queensland, Australia.

Other reefs are formed from single ships, such as the retired 510-foot (155.5-meter) USS Spiegel Grove, which was sunk in 2002 off Key Largo, Florida, and is now the foundation of a thriving reef. Spiegel Grove is one of several decommissioned ships sunk in the area after the designation of the Florida Keys National Marine Sanctuary. The 910-foot (277.4-meter) USS Oriskany, an aircraft carrier that served during the Korean War and Vietnam War, was sunk in the Gulf of Mexico off the coast of Florida’s panhandle in 2006. Planned as the largest artificial reef in the world, the SS United States—a 990-foot (301.7-meter) ocean liner which ferried immigrants and celebrities alike across the Atlantic Ocean between 1952 and 1969—was sunk some 12 nautical miles (22.2 km) from the final resting place of the Oriskany in November 2026,

Rigs-to-reefs

Offshore oil and gas platforms quickly become attractive habitats for marine organisms. Once these platforms are decommissioned, companies are required to remove the structures. However, in 1985 the United States government began the National Artificial Reef Plan, which laid the legal groundwork for oil and gas platforms to be transformed into artificial reefs. The five states surrounding the Gulf of Mexico—Alabama, Florida, Louisiana, Mississippi, and Texas—all participate in the “rigs-to-reefs” program and now have decommissioned platforms acting as artificial reefs in their waters. Other countries, such as Malaysia, Thailand, and Australia, have implemented similar practices.

There are several ways to transform oil and gas platforms into reefs. First, the oil wells are sealed, and the unsubmerged platform is removed. Workers may simply topple the foundations or separate the structure at a certain depth, laying the top part on the ocean floor next to the bottom. In some cases they may use explosives to detach the entire platform from the ocean floor and tow it to a different location. Not all platforms are eligible; they must meet environmental and engineering standards.