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Artificial Reefs in the U.S.A.

By: Monterey Rayman

The fight to conserve our natural reefs is becoming more complicated by the day. About 30-50% of natural coral reefs are gone and an increase in environmental stressors is creating a hostile environment, making it difficult for coral growth. Coral reefs are biodiverse marine ecosystems that support an abundance of species. Along with supporting a host of different species, reefs also service us. They support our economy, reduce water pollution through their filter feeding abilities, and minimize wave action to help prevent shoreline and seafloor erosion. ‘Coral gardening’ has been on the frontlines in the battle against coral degradation, however, artificial reefs have sparked new optimism for coral reef restoration. The concept of an artificial reef started in the 1800s, but the movement towards establishing artificial reefs didn’t quite start until the 1950s. There have been several different methods of artificial reef construction that were experimented with resulting in a mix of success and failure. Are artificial reefs the solution to rejuvenating and restoring local marine ecosystems?

A recent study worked to quantify the artificial reef footprint of the surrounding U.S. oceans. An analysis of this size had not been done before and will prove to be helpful in future artificial reef development. Spatial data was used in combination with the 17 US coastal states with ocean reefing programs to determine reef zones and permitted reefing zones. The current footprint for known artificial reefs is equivalent to 3,594 football fields. Of the mapped seafloor, 99.67% is available for the creation of artificial reef structures. From 1970-2020 the footprint has increased 21-fold, but started to slow down about 1-fold in the past decade. The decrease in the rate of artificial reef development in the past decade can be due to focused efforts on the restoration of natural reefs as opposed to development. 

For the success of an artificial reef, certain things need to be taken into consideration. The space, the material, the distance between reefs, the currents, and the recreational potential are just a few of the things to consider. In general, decommissioned material is encouraged for artificial reef projects as it helps repurpose the material and is affordable. Unfortunately depending on the material being used it may degrade faster, be unstable, leach toxins, and not provide the complex surfaces ideal for a diverse reef community. The material of the reef structure must be non-toxic, and durable enough to withstand strong storms and currents. If the structure of the artificial reef starts moving around it can potentially damage reefs nearby and move from its ideal location. Degrading material can release toxins that can pollute local waters and create habitats ideal for invasive species. Material like PVC is too smooth for coral to readily attach to, isn’t durable, and is too light. Tires shouldn’t be used because they can move a lot during storms, possibly causing damage to nearby reefs and washing up on the shoreline. Cinder blocks have been used as well, but the material is too light, and it breaks easily. 

It’s found that concrete structures that were made with reef-use intention have a higher success rate, but require more funding. Although it is more expensive, using structures built to mimic a natural reef with all of its complexities will increase the chances of success for an artificial reef project. Artificial reef sites with unique concrete structures with transplanted coral had faster restoration success. These structures achieved a similar state to that of natural reefs within a couple of years of monitoring. In comparison, artificial reefs resulting from an accident (shipwreck, etc.) can take decades to form and typically have less unique taxon. The use of either concrete, rock, or metal has had the most success. Some companies are even 3D printing concrete reef structures. 

Artificial reefs can be key in sustaining marine biodiversity and supporting local coastal communities. The success of an artificial reef can look different depending on project goals. It can be an increase in biomass or even the use of the reef by key species' typically found at a natural reef nearby. An important part of the success of an artificial reef is consistent monitoring even after goals are met. With consistent monitoring, timely intervention is possible for issues involving invasive species, overfishing, or other issues with reef establishment. Local reef systems should be monitored for change as well. Each local marine ecosystem will have its own unique needs for success in that region. Artificial reefs have come a long way and as the field grows, more research and efficient monitoring will provide new insights into new contributions and downfalls. Artificial reefs are one approach to ecosystem-based solutions. When implemented thoughtfully they have the potential to leave a lasting positive impact on a community. 


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