The concept of an artificial reef has been used by humans for many centuries. Therefore, there are many different types and methods. It is stated that ‘when properly designed, located and constructed with an adequate quantity of stable and durable substrate, man-made reefs can be equally as productive in theory as naturally occurring hard- bottom habitats, limited only by the life-span of the materials utilized.’ Many materials do exist that are effective, durable and rather inexpensive.
Decision makers have to deal with two important factors when deciding upon an artificial reef: the economic and the ecologic value. Artificial reefs are supposed to affect both the ecological and the economical value, the latter mainly through recreational income and fishing opportunities. For a successful process it is important to clearly define the costs and incomes on these aspects.
In terms of resistance of the public, ecological and coastal protection reefs are easier accepted by the public, where surf reefs tend to get more opposition. When combining the opportunities in a multipurpose reef, most benefits can be achieved.
The environmental aspects of artificial reefs are mainly positive. Artificial reefs can be used to create new habitat for marine flora and fauna and can have an accelerating effect on the biodiversity and productivity of the area. Research shows that the organisms that are attracted to the artificial reef create new sources of food, which attracts other species. Mature artificial reefs, of around 3-5 years old, play a significant role in the increasing biodiversity. However, also a number of remarks need to be made on the environmental effects of artificial reefs.
Firstly, using recycled materials appeared to be cost and environmental effective. However, not all materials were completely risk-free. Tires would break loose and damage the natural reefs and certain types of steel cause corrosion that is very harmful for the environment. Also the effect of these structures in 100 or 200 years is unknown. Secondly, although it is recognized that artificial reefs attract fish, it needs to be questioned whether a reef really promotes new populations to grow or it only attracts existing populations to a richer location. Not in all cases it is proven that artificial reefs enhance the fish population or just affect relocation.
Another negative effect of artificial reefs can be intensification and over-fishing. Because reefs have a high density of fish, it makes a very good fishing spot.
Overall, from the different artificial reefs it can be concluded that most artificial reefs in seas and oceans do enhance biodiversity, -productivity and -mass as the hard substrates used are very different from the natural seabed and ideal for marine flora and fauna. However, the material chosen to use does make a difference on the type of species that can be found on the reef and how much the biomass will increase.
Public acceptation is a topic that returns in all projects, as it can be used to derive attention from natural reefs, it can prevent abuse of the reefs and is necessary for the success of artificial reefs.