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Construction in place of an artificial reef from concrete blocks
Tires being placed in an array to determine their effectiveness as habitat for fish.

An artificial reef is a man-made, underwater structure, typically built for the purpose of promoting marine life in areas of generally featureless bottom. Artificial reefs may also serve to improve hydrodynamics for surfing or to control beach erosion.

Artificial reefs can be built in a number of different methods. Many reefs are built by deploying existing materials in order to create a reef. This can be done by sinking oil rigs (through the Rigs-to-Reefs program), scuttling ships, or by deploying rubble, tires, or construction debris. Other artificial reefs are purpose built (e.g. the reef balls) from PVC and/or concrete. Historic or modern shipwrecks become unintended artificial reefs when preserved on the sea floor. Regardless of construction method, artificial reefs are generally designed to provide hard surfaces to which algae and invertebrates such as barnacles, corals, and oysters attach; the accumulation of attached marine life in turn provides intricate structure and food for assemblages of fish.

Contents

History

The construction of artificial reefs is thousands of years old, although the historic usages were related to sea power rather than aquaculture. Ancient Persians blocked the mouth of the Tigris River to thwart Indian pirates by building an artificial reef,[1] and during the First Punic War the Romans built a reef across the mouth of the Carthaginian harbor in Sicily to trap the enemy ships within[2] and assist in driving the Carthaginians from the island.

The use of artificial reefs to increase fish yields or for algaculture also has a long history. During the 1600s reefs of building rubble and rocks were used in Japan to grow kelp,[3] while the earliest recorded construction of artificial reef in the United States is from 1830s when logs from huts were used off the coast of South Carolina to improve fishing.[4]

In the early 1970s, a series of thousands of disused vehicle tires were dumped off the coast of Fort Lauderdale, Florida to form an artificial reef, causing environmental problems over time. See Fort Lauderdale tire reef.

Surplus Redbird cars pass under the George Washington Bridge on the way to being sunk to form an artificial reef.

In late 2000, The MTA New York City Transit decided to phase out its outdated fleet of subway cars to make room for the R142 & R142A trains. These subway cars, commonly referred to as Redbirds, ran on the IRT lines in the New York City Subway system for over 40 years. Each car was sold, stripped, decontaminated, loaded on a barge, and sunk in the Atlantic Ocean. In some cases, a few of the cars had their number plates removed because of rust. Over 1,200 subway cars were sunk.

In September 2007, the MTA approved a contract, worth over $6 million , that would send more than 1,600 of its retired subway cars to be used as artificial reefs. Most of these trains ran on The BMT/IND lines. The trains include the R32, R38 , R40 and R42. These models are made of stainless steel. The MTA will replace them with the R160A & R160B trains. Workers removed the plastic front ends found on most of the cars before sinking. The retired fleet also included old work trains and cars damaged beyond repair.

The world's largest artificial reef was created by the purposeful sinking of the USS Oriskany off the coast of Pensacola, Florida, in 2006. The second-largest will be the USNS Hoyt S. Vandenburg, a former World War Two era troop transport that served as a spacecraft tracking ship after the war. The Vandenburg was scuttled seven miles off Key West on May 27, 2009, in 140 feet of clear water.[5] Supporters expect the ship to draw recreational divers away from natural reefs, allowing those reefs to recover from the damage caused by overuse.[6]

Artificial surfing reefs

Man made objects provide hiding places for marine life, like this Sarcastic fringehead

Artificial surfing reefs have been created for surfing, coastal protection, habitat enhancement and coastal research. The world's first attempt was made in El Segundo, near Los Angeles, in California. The next attempt was at Cable Beach, Perth, Western Australia. This reef was constructed of large granite rocks placed in a pyramidal shape to form an appropriate breaking wave form that would suit surfers. An artificial reef constructed of over 400 massive, geotextile bags (each one larger than a bus) filled with sand was constructed in 2000 at Narrowneck on the Gold Coast of Queensland, Australia. This artificial reef had two objectives: stabilizing beach nourishment and improving surfing conditions.

Artificial surfing reefs typically resemble a "submerged breakwater", and proponents suggest additional benefits beyond surfing conditions. Many coastlines are subject to powerful waves that crash directly onshore. An artificial reef situated 150-300 yards offshore might create surfing opportunities and, by dissipating wave energy, make swimming safer and reduce coastal erosion.

The USS Spiegel Grove was sunk in 2002 to make an artificial reef. In the United States, in particular, demanding coastal permit requirements and environmental opposition present major obstacles to building surfing reefs. As of February 2006, the only reef built in the U.S. specifically for surfing is southern California's "Pratte's Reef", which failed to create waves. Reefs built to enhance marine habitat face far less environmental opposition, in part because they are in much deeper water and further offshore. A number of such man-made reefs exist near Florida and Hawaii.

Europe's first artificial reef was approved in 2008. Construction began 30 August 2008 in Boscombe, Bournemouth, UK, and opened in November 2009. The multi-purpose reef reef is expected to create waves up to 30% larger and double the number of surfing days annually. Construction on this reef began in June 2008, and was completed in August 2009.[7] Boscombe Reef was built from large sand-filled geotextile containers, totaling 13,000 cubic meters.

Electro Mineral Accretion (EMA)

USS Oriskany being sunk to create a reef

Mineral accretion involves applying a low voltage current to a metallic structure to cause limestone to crystallize on the surface, to which coral planulae can attach and grow. The electric current also speeds post-attachment coral growth.[8]

EMA works like charging a battery with a positive pole, the cathode, and a negative pole, the anode. Applying electric current attracts various dissolved minerals to either the cathode or the anode. Chemical reactions then 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.

The voltage is low enough that it can be generated by floating solar panels or from wave motion.

A coalition of scientists named the Global Coral Reef Alliance (GCRA)[8] is developing a technique called the Biorock Process using mineral accretion for reef restoration, mariculture, and shoreline protection.

Environmental concerns

Reports about environmental damages caused by "tire reefs" have prompted questions about the risks of creating artificial reefs.

A multi-million-dollar cleanup of Osborne Reef, a tire dump near Fort Lauderdale, Florida is underway. The tires started posing a particular threat after breaking free from the reef

According to The Ocean Conservancy, a Washington-based environmental group, the Florida reef may be an indication that the benefits of artificial reefs need to be re-examined. Jack Sobel, a senior scientist at the group, has said "There's little evidence that artificial reefs have a net benefit.".[9]

See also

References

  1. ^ Thomas Wayne Williams, A Case Study of Artificial Reef Decision-Making in the Florida Keys, Virginia Commonwealth University [1]. Retrieved 20 December 2006.
  2. ^ Ron Hess, Denis Rushworth, Michael V. Hynes, John E. Peters, Disposal Options for Ships, Chapter 5, "Reefing," Rand Corporation, [2]. Retrieved 20 December 2006.
  3. ^ Fisheries Technologies for Developing Countries, National Academies Press [3]. Retrieved 20 December 2006.
  4. ^ Gulf States Marine Fisheries Commission, GUIDELINES FOR MARINE ARTIFICIAL REEF MATERIALS, [4]. Retrieved 20 December 2006.
  5. ^ "WWII-era ship becomes sunken reef off Key West , AT&T Online News, May 27, 2009". My.att.net. 1985-01-01. http://my.att.net/s/editorial.dll?fromspage=cg/news/ne_details.htm&eeid=6592684&eetype=article&render=y&ch=ne&s=na. Retrieved 2009-07-18.  
  6. ^ Ship to Become 2nd Largest Intentional Reef , Associated Press, published in New York Times, May 25, 2009, retrieved May 25, 2009
  7. ^ http://www.bournemouthecho.co.uk/news/features/surfreef/surfreefstories/4716058.Optimism_at_Boscombe_surf_reef___s_opening_day/
  8. ^ a b "Global Coral Reef Alliance". http://www.globalcoral.org/. Retrieved 2009-07-18.  
  9. ^ "Florida Raises Ill-Fated Artificial Reefs". Enn.com. 2007-07-09. http://www.enn.com/top_stories/article/6895. Retrieved 2009-07-18.  

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