Artificial reefs are a restoration method used to restore activity in natural reefs where coral bleaching and deterioration have occurred. Artificial reefs have been used for many years with records dating back to the 17th century when the Japanese used rubble and rocks to grow kelp. Another time in history where artificial reefs appear is in the mouth of the Tigris River when the ancient Persians were attempting to prevent Indian pirates from invading their territories. As for recent years, sunken ships, oil rigs, and discarded refrigerators have become the new artificial reefs. So what exactly is an artificial reef?
In simple terms, an artificial reef is a hard surface provided for reef life to attach to and grow on. These hard surfaces can be a variety of objects such as accidentally sunken ships, deliberately sunken ships, oil rigs, construction debris, old tires, PVC pipping, or concrete. As the reef life attaches to these hard surfaces, shelter and food start to become more abundant; which in turn increases activity of both coral and fish but also humans. What makes them a good restoration project is that is grows in predictable stages. And where there is positive, there is always negative.
While many were put in with good intentions, they have been causing the effects of bleaching and deterioration to rise to new extremes as more stress in placed on the coral. Some materials are larger causes for concern over others. One of these is tires. Tires are a widely used foundation for artificial reefs across the world but have started to raise some red flags as their properties are examined. Tire manufacturers compose their tires differently from one company to the next but most have similar chemicals. These are black carbon, sulphur, zinc oxide, and peroxides, which are found in most tires that have been found in the oceans. Though there is little evidence suggesting that rubber formulas do not release harmful chemicals into the oceans, the US National Artificial Reef Plan state that tires are still a good construction material for artificial reefs.
Even though the lack of evidence is significant, the use of tires as artificial reefs has become less favorable among marine biologists. The washing up of tires onto beaches during tropical storms causes nearby coral reefs a fair amount of damage as well as preventing new growth as debris tears through them. Since this has been happening, Florida and France have started the wide-scale removal of tire built reefs from their waters. 130,000 of 700,000 tires have been removed from the oceans as of 2007. Now the Ocean Conservancy includes tire removal alongside the International Coastal Cleanup every September.
Another negative impact the artificial reefs have made is an unusually large amount of fish attraction. At first, this sounds like a benefit or good effect of the artificial reef but when examined under a closer eye, it turns out this is even more harmful to the natural reefs than if it was not there at all. The attraction of fish was a positive attribute when concerned with fisherman, as this causes many fish to gather in a more concentrated area. The problem is that over-fishing was a stress on natural reefs to begin with.
While artificial reefs don't increase fish populations, they serve as a congregation area for them. Extra research must be conducted to find out if the attraction of fish to these areas is actually making up for the loss of their appearances in natural reefs. The attraction of fish varies from reef to reef and more often that not artificial reefs attract more fish than the surrounding natural reefs. As for the kinds of fish each artificial reefs attracts, age, size, and structure are all large factors. In general, the larger the structure, the larger the fish that it will attract. Sunken ships will attract larger fish such as jacks and Barracuda. Smaller reefs can attracts other kinds of fish such as sardines and minnows.
All in all, artificial reefs have benefits as well as disadvantages that can bring harm the natural reefs while their intended use was to rebuild them. This is not the only form of reef restoration but it has made a larger impact on the public than other forms have. Next time I will be researching coral transplants so that I have even more knowledge on the two most used forms of coral reef restoration.
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