Artificial reef

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An artificial reef is a reef that would not have developed naturally in this form at the place where it is located. That is, it was created through human intervention. These interventions can be intentional or unintentional. Sunken ships , crashed aircraft or vehicles that have crashed into the sea near a port can form the basis of an artificial reef. In addition, there have recently been submerged structures such as dolosse , reef balls , tetrapods or quadripods , or old car tires, specifically to promote reef formation .

Unintentional artificial reefs

The number of accidentally formed reefs that can be traced back to human intervention far exceeds that of intentionally created reefs. The largest such reefs arise when ships sink. For example, the former German heavy cruiser Prinz Eugen has been forming such an artificial reef in the Kwajalein Atoll since it capsized in 1946 .

Intended artificial reefs

Oriskany at the sinking

Initially, these reefs were created to study the flora and fauna found in the sea by oceanographic institutes. With this knowledge, artificial reefs were then created in biologically less active regions, for example the decommissioned frigate Scylla off the British coast. The wreck is now at a depth of approx. 21 m off the coast of Cornwall and has therefore been left to the marine life to colonize.

The largest artificial reef is currently the Oriskany Reef , which the former aircraft carrier USS Oriskany (CV-34) forms off the coast of Pensacola , Florida state in the Gulf of Mexico . The ship was sunk on May 17, 2006, 41 km south of Pensacola, after removing almost all materials potentially harmful to the environment. Care was taken to ensure that the ship did not capsize, so that the 25 m high bridge remained accessible to scuba divers at a depth of around 17 m.

The Osborne Reef off Fort Lauderdale (Florida / USA) - which was expanded in the 1970s with millions of old car tires - has turned out to be an ecological disaster. Artificial reefs made from car tires have also been created elsewhere.

Artificial coral reefs

Concrete and stone structures can be colonized by corals at suitable locations ; however, this process is very tedious. Biorock technology in particular offers opportunities to build artificial coral reefs in a short time . Steel structures are sunk and put under direct current . This causes mineral accretion on the steel. Broken corals are attached to this limestone deposit , which attach to it and reproduce well. These artificial reefs have already been realized in the Caribbean and Asia.

Function of artificial reefs

The latest development is in the direction of the engineering planning of artificial reefs for goals such as coastal protection , wave profile for surfing , creation of fishing grounds for tourist purposes such as scuba diving (for example the Henry Bonneaud off the coast of Vanuatu ), fishing etc.

It is currently difficult and expensive to build reefs that meet all requirements. The first reefs were established with the help of 50-ton sand containers. Huge plastic bags are filled with sand and then brought out to sea by special ships and sunk with the help of a hinged hull. However, with this method, the alignment of the sand containers cannot be controlled precisely enough to give the reef an ideal flow dynamic shape.

A project was started on the sandy beaches of the Australian Gold Coast in 1998, which was primarily intended to protect the beach from storm surges and erosion . At the same time, the artificial reef should offer surfers ideal wave shapes. The world's first artificial surf reef was built in 2000 at Narrow Neck on the Gold Coast. Here, too, sand containers made of synthetic fabric were sunk. Since then, the 10 million dollar reef has fulfilled its function as a breakwater to the satisfaction of the client. The artificial reef was populated by plants and animals surprisingly quickly, as the surface of the sand container made of fiber fabric makes it easier for living beings to anchor. Algae and seaweed were the first plants, and certain corals also settled there. Numerous fish attract not only sport anglers, but also cormorants . However, the “perfect wave” for the surfers could not be produced on the Narrow Neck Reef.

Common starfish on the artificial reef Nienhagen

Another multifunctional reef is currently being installed off the coast of Tauranga in New Zealand . Surfing is in the foreground on the reef built near the seaside resort of Mount Maunganui. In order to realize the shape of the reef as planned, a network of tear-resistant straps was anchored to the seabed, to which the empty sand containers were already attached. These sand containers are now being filled up from the coast via a pipeline. However, there were repeated difficulties with the subsequent filling.

With tetrapods and other concrete components, the Nienhagen reef was created off the coast of the Baltic Sea , which is currently used for research purposes and shows that recourse to artificial reefs can also be useful for the maintenance of commercial fish.

See also

Individual evidence

  1. ↑ Bauernfeind, Ingo: Radioactive to all eternity - The fate of the Prinz Eugen . ES Mittler & Sohn, Hamburg / Berlin / Bonn 2011, ISBN 978-3-8132-0928-0 , p. 129 .
  2. ↑ Current status of the construction work on Mountreef ( Memento of December 28, 2010 in the Internet Archive ) (August 2007)

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