Artificial reef

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Constructing an artificial reef using concrete blocks
Tires being placed in an array to investigate their effectiveness as a fish habitat.

An artificial reef is a human-made underwater structure, typically built to promote marine life in areas with a generally featureless bottom, to control erosion, block ship passage, or improve surfing.

Many reefs are built using objects that were built for other purposes, for example by sinking oil rigs (through the Rigs-to-Reefs program), scuttling ships, or by deploying rubble or construction debris. Other artificial reefs are purpose built (e.g. the reef balls) from PVC or concrete. Shipwrecks may become artificial reefs when preserved on the sea floor. Regardless of construction method, artificial reefs generally provide hard surfaces where 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.

History[edit]

The construction of artificial reefs is thousands of years old. 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.

Artificial reefs to increase fish yields or for algaculture have been used at least since 17th century Japan, when rubble and rocks were used to grow kelp,[3] while the earliest recorded construction of artificial reef in the United States is from the 1830s when logs from huts were used off the coast of South Carolina to improve fishing.[4]

Since at least the 1830s, American fishermen used interlaced logs to build artificial reefs. More recently, castaway junk, such as old refrigerators, shopping carts, ditched cars, out-of-service vending machines replaced the logs in ad hoc reefs. Officially sanctioned projects have incorported decommissioned subway cars, vintage battle tanks, armored personnel carriers and oil drilling rigs.[5]

Development[edit]

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 like bluefin 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, waiting for their prey to venture out. Over months and years the reef structure becomes encrusted with algae, tunicates, hard and soft corals, and sponges.[5]

Artificial surfing reefs[edit]

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

Artificial surfing reefs have been created in several locations around the world. Supporters cite subsidiary benefits such as 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 Mosman 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.

Europe's first artificial reef was approved in 2008. Construction began August 30, 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.[6] Boscombe Reef was built from large sand-filled geotextile containers, totaling 13,000 cubic meters.

In the United States demanding coastal permitting requirements present major obstacles to building surfing reefs. As of February 2006, the only reef built in the U.S. for surfing is southern California's "Pratte's Reef", which failed to create waves.

The surfing mecca of Hawaii in particular reflects political realities that make construction of artificial surfing reefs unlikely. The state's coastal strict zoning requirements are dovetailed by a strong ocean protection ethic that looks askance at any coastal modification. In simple terms, this ethic holds that “it is best to leave the ocean in its natural state.”

A second factor is “Nimbyism.” In contrast to many coastal communities worldwide, Hawaii has a large number of single-family homes abutting its coastlines. Beach parks are often small and intermittently sited. Public access along home-girded coastlines is a contentious issue; access points to the coast are increasingly restricted. The prospect that an artificial reef is to be built off a community would raise homeowner concern about an influx of beach visitors—and the attendant noise, traffic and lack of privacy.

Liability concerns is a third factor. Statewide, both coastal landowners and Hawaii government have been subject to lawsuits for injuries and death occurring along coastlines. Partial relief was provided by the Hawaii State Legislature years ago—people bear major responsibility for their actions near the ocean, according to changes in the law. But this is for coastal areas in a natural state. The modification of a coastline to attract ocean users the likelihood that government authority will be deemed partially responsible for any injuries. Artificial surfing reefs, like swimming pools, can be viewed as an attractive nuisance.

Reefs built to enhance marine habitat face less environmental opposition, in part because they are in deeper water and further offshore. A number of such man-made reefs exist near Florida and Hawaii.

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

Electro mineral accretion (EMA)[edit]

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 growth.[7]

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 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)[7] is developing a technique called the Biorock Process using mineral accretion for reef restoration, mariculture, and shoreline protection.

Environmental concerns[edit]

According to The Ocean Conservancy, a Washington-based environmental group, the Osbourne 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," citing concerns such as toxicity, damage to ecosystems and concentrating fish into one place (worsening overfishing).[8]

Examples[edit]

Florida[edit]

Florida is the site of many artificial reefs, many created from deliberately sunken ships, including Coast Guard cutters Duane and Bibb and the U.S. Navy landing ship Spiegel Grove.[5]

Osborne Reef[edit]

Main article: Osborne Reef
A bed of skummy tires rests piled upon the ocean's floor; a small yellow fish swims by the left.
Tires constituting Osborne Reef (2007)

In the early 1970s, more than 2,000,000 used vehicle tires were dumped off the coast of Fort Lauderdale, Florida to form an artificial reef. Catastrophically, the tires were not properly secured to the reef structures. Ocean currents broke them loose, sending them crashing into the developing reef and its natural neighbors. As of 2009, less than 100,000 of the tires had been removed after more than 10 years of efforts.[9]

Neptune Reef[edit]

Neptune Reef was originally conceived as an art project that would gradually decay. Burial at sea became a way of financing the project. As of 2011, about 200 "placements" had taken place. Cremated remains are mixed with cement and either encased in columns or molded into sea-star, brain-coral, 15 foot-tall castings of lions or other shapes before entering the water.[5]

Ex-USS Oriskany[edit]

Sea life growing on the remains of the USS Oriskany, intentionally sunk in 2006 to become an artificial reef.

The world's largest artificial reef was created by the purposeful sinking of the aircraft carrier USS Oriskany off the coast of Pensacola, Florida, in 2006 with a massive role in sand erosion.[10]

Ex-USNS Hoyt S. Vandenberg[edit]

The second-largest artificial reef is the USNS Hoyt S. Vandenberg, a former World War II era troop transport that served as a spacecraft tracking ship after the war. The Vandenberg was scuttled seven miles off Key West on May 27, 2009, in 140 feet of clear water.[11] Supporters expect the ship to draw recreational divers away from natural reefs, allowing those reefs to recover from damage from overuse.[12]

Ex-USS Spiegel Grove[edit]

The ex-Spiegel Grove is located on Dixie Shoal, 6 miles (10 km) off the Florida Keys in the Florida Keys National Marine Sanctuary. Her exact location is 25°04′00.23″N 80°18′00.7″W / 25.0667306°N 80.300194°W / 25.0667306; -80.300194.

Delaware[edit]

Redbird Reef[edit]

Main article: Redbird 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 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 IRT lines in 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 1200 subway cars were sunk for this project.

In September 2007, the MTA approved a further contract worth $6 million[citation needed], to send 1600 of its retired subway cars to be used as artificial reefs. Most of these trains had run on the BMT/IND lines. The trains included the R32, R38, R40, and R42. The MTA has replaced them with the R160A and R160B trains. The old models were sheathed in stainless steel, except for the plastic front ends, which were removed before sinking. The retired fleet included old work trains and cars damaged beyond repair.

Mexico[edit]

Cancun Underwater Museum[edit]

Since November 2009, artist Jason Decaires Taylor has created more than 400 life size sculptures off the coast of Cancun, Mexico. The coral reefs in this region suffered heavy degradation due to repetitive hurricane abuse. This project funded by The National Marine Park and the Cancun Nautical Association was designed to emmulate coral reefs using a neutral ph clay. Taylor has constructed unique settings depicting daily activities ranging from a man watching TV to a 1970's replica of a Volkswagen Beetle. This artificial reef has relieved pressure from the nearby Manchones Reef. The design and materials implemented in this project have proved the ecological viability of artificial reefs.[13]

Australia[edit]

Since the late 1990s, the Australian government has been providing decommissioned warships for use as artificial reefs for recreational scuba diving. So far, the following six ships have been sunk:

Gibraltar[edit]

The Gibraltar Reef was first proposed by Eric Shaw in 1973. Initial experiments with tires proved unsuccessful as the tires were simply swept away by currents or buried underneath sand. In 1974, boats from local marinas and the Gibraltar Port Authority were donated. The first two were barges that were sunk in Camp Bay. In 2006, a 65 ton wooden boat, "True Joy" (also referred to as "Noah's Ark") was sunk here as well, followed by the MV New Flame, a mid sized bulk carrier, in 2007.

In 2013, a dropping of more than 70 concrete blocks, each one square meter with metal bars, took place. This led to heated debate between the United Kingdom and Spain, with Gibraltar accusing Spain of over forty incursions into their waters per month[19] and Spain accusing Gibraltar of including metal bars in the reef to stop Spanish fishermen trawling the seabed for fish. The dropping lead to a diplomatic conflict between the Kingdom of Spain and the United Kingdom due to Gibraltar being a British Overseas Territory.

India[edit]

Temple Reef[edit]

Main article: Temple Reef

It is an artificial reef off the coast of Pondicherry, India constructed of fully recycled materials such as concrete, rocks, trees, palms, and iron bars. It is located at the depth of 18 m (60 feet).

See also[edit]

References[edit]

  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 December 20, 2006.
  4. ^ Gulf States Marine Fisheries Commission, GUIDELINES FOR MARINE ARTIFICIAL REEF MATERIALS, [4]. Retrieved December 20, 2006.
  5. ^ a b c d "Artificial Reefs". National Geographic. February 2011. Retrieved April 30, 2011. 
  6. ^ "Optimism at Boscombe surf reef’s opening day (From Bournemouth Echo)". Bournemouthecho.co.uk. 2009-11-03. Retrieved 2012-06-19. 
  7. ^ a b "Global Coral Reef Alliance". Retrieved 2009-07-18. 
  8. ^ "Florida Raises Ill-Fated Artificial Reefs". Enn.com. 2007-07-09. Retrieved 2009-07-18. 
  9. ^ Peppard, Jim (2009-08-21). "Florida tire reef removal ends for the year". St. Petersburg, Florida, USA: WTSP. Archived from the original on 2010-12-01. Retrieved 2010-12-01. 
  10. ^ Olsen, Erik (2008-08-19). "Out of Commission Above Water, but Not Below It". The New York Times. 
  11. ^ "WWII-era ship becomes sunken reef off Key West, AT&T Online News, May 27, 2009". My.att.net. 1985-01-01. Retrieved 2009-07-18. 
  12. ^ Ship to Become 2nd Largest Intentional Reef , Associated Press, published in New York Times, May 25, 2009, retrieved May 25, 2009
  13. ^ "Cancun’s Underwater Museum Blooms In Time For Spring". Cancun Visitors Bureau. Retrieved 15 November 2012.
  14. ^ 'HMAS Swan - History,' http://www.michaelmcfadyenscuba.info/viewpage.php?page_id=454, retrieved 12/07/2012.
  15. ^ 'Welcome to the official former HMAS Perth Website,' http://www.hmasperth.com.au/, retrieved 12/07/2012..
  16. ^ 'Dive the Ex-HMAS Hobart,' http://www.exhmashobart.com.au/index.html.
  17. ^ 'Ex-HMAS Brisbane Conservation Park,' http://www.derm.qld.gov.au/parks/ex-hmas-brisbane/index.html, retrieved 12/07/2012.
  18. ^ 'ex-HMAS Canberra Reef,'http://www.hmascanberra.com.au/, retrieved 12/07/2012.
  19. ^ http://www.express.co.uk/news/world/443937/GIBRALTAR-We-are-just-one-shot-away-from-military-conflict-warns-MP-amid-new-standoff