Shipwrecks Sunk as Artificial Reefs

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.

Many reefs are built using objects that were built for other purposes, such as by sinking oil rigs (through the Rigs-to-Reefs program), scuttling ships, or 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 seafloor. 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 structures and food for assemblages of fish.

Artificial reefs can show quick increases in local fish population rehabilitation, coral reef, and algae growth. However, far more than half the amount of biomass found on artificial reefs is attracted from other areas rather than developing there. Artificial reefs do not increase fish populations. Instead, they operate as fish aggregating devices bringing in fish from other reefs. Concentrating fish on a reef also makes for easier fishing.

The fish attracted to artificial reef zones vary from reef to reef depending on their age, size, and structure. Large reef structures such as large sunken ships attract larger fish.

The use of shipwrecks in rocky zones creates a new trophic structure for the local ecosystem. They become the home for certain species and many nearby animals migrate to the shipwreck. This unbalances the natural ecosystem and has the potential to alter many other habitats.

Thousands of popular wreck diving sites throughout the world are shipwrecks sunk as artificial reefs. Some of these wrecks were sunk deliberately to attract divers. The USS Spiegel Grove and USS Oriskany in Florida, USS Indra and USS Aeolus in North Carolina, and Bianca C. in Grenada draw thousands of divers annually.

There are many factors that can make an artificial reef a success or failure, and even the same techniques and materials may work well in some situations and not in others.

The materials used in most artificial reefs often cause pollution by releasing chemicals and nutrients that are not naturally found in reef environments. Ships can release polychlorinated biphenyls (PCBs), asbestos, iron, lead paint, and anti-fouling paint leaches into the ocean and enters the food chain.

It is important to recognize that artificial reefs only work in areas where water quality is still conducive to coral growth. Artificial reefs are a great tool for marine resource managers, but it is only one tool on our belt. It needs to be used in conjunction with a wide variety of other actions such as establishing rules and regulations, reducing local land and sea-based threats, reducing over-fishing/over-use, and other mitigation or protection methods to create an effective and holistic coral reef restoration program.

#Nature #Underwater #CoralReef