An artificial reef is a human-created underwater structure, typically built to promote marine life in areas with a generally featureless bottom, to control erosion, block ship passage, block the use of trawling nets, or improve surfing.
Beginning before the 1840s, US fishermen used interlaced logs to build artificial reefs. More recently, refuse such as old refrigerators, shopping carts, ditched cars and out-of-service vending machines replaced the logs in ad hoc reefs. Officially sanctioned projects have incorporated decommissioned ships, subway cars, battle tanks, armored personnel carriers, oil drilling rigs and beehive-like reef balls.
Artificial reefs tend to develop in more or less predictable stages. First, where an ocean current encounters a vertical structure, it can create a plankton-rich upwelling that provides a reliable feeding spot for small fish such as sardines and minnows, which draw in pelagic predators such as tuna and sharks. Next come creatures seeking protection from the ocean's lethal openness—hole and crevice dwellers such as grouper, snapper, squirrelfish, eels and triggerfish. Opportunistic predators such as jack and barracuda also appear. Over months and years the reef structure becomes encrusted with algae, tunicates, hard and soft corals and sponges.
EMA works like charging a battery with a positive pole, the cathode, and a negative pole, the anode. Applying electric current attracts dissolved minerals to either the cathode or the anode. Chemical reactions take place at both poles. On the anode, bubbles of oxygen and chlorine gas form. These bubbles float to the surface and dissolve into the air. On the cathode, bubbles of hydrogen gas and a limestone precipitate appear.
Europe's first artificial reef was approved in 2008. Construction began August 30, 2008, in Boscombe, Bournemouth, UK (5 months after 3 local councillors spent 18 days in New Zealand on a fact-finding mission), and opened in November 2009. The ă3 million (2.5% of the Council's annual budget that year) reef was expected to create waves up to 30% larger and double the number of surfing days annually. Construction on this reef continued from June 2008 through August 2009. Boscombe Reef was built from large sand-filled geotextile containers, totaling 13,000 cubic metres (460,000 cu ft). It failed entirely and attempts were made to convert it into a multi purpose reef, which also failed. Bournemouth Council attempted to recover monies from the New Zealand-based reef construction company but the company went into administration before paying any compensation.
Old tires were used to create many artificial reefs. In Florida alone, 571 permitted artificial reefs exist, and the number of illegal reefs is thought to be much greater. Tires are made from many chemicals and compounds such as black carbon, sulphur, zinc oxide and peroxides. The US National Artificial Reef Plan states that tires are a good reef construction material because no toxic substances are released from the decomposition of tires; though there is little information published to back up the claims and the future decomposing of the many different types of rubber tires could create unseen pollution.
In 1921 the US battleship Massachusetts was scuttled in shallow water off the coast of Pensacola, Florida and then used as a target for experimental artillery. In 1956 the ship was declared the property of the state of Florida by the Florida Supreme Court. Since 1993 the wreck has been a Florida Underwater Archaeological Preserve and is included in the National Register of Historic Places. She serves as an artificial reef and diving spot.
In late 2000, the New York City Transit Authority decided to retire an outdated fleet of subway cars to make room for new R142 and R142A trains. The obsolete subway cars, (nicknamed "Redbirds"), had run on the A Division (former Interborough Rapid Transit Company routes) of the New York City Subway system for 40 years. Each car was stripped, decontaminated, loaded on a barge, and sunk in the Atlantic Ocean off the coast of Delaware. Some cars had number plates removed because of rust, which were then auctioned off on eBay. A total of 1,200 subway cars were sunk for this project.