This post contributed by Nadine Lymn, ESA Director of Public Affairs
Typically the size of a football field and reaching a height of several hundred meters, the production life of an offshore oil or gas rig is over once it’s drained its location’s energy supply. Then a company must retire and remove the rig.
Conceived by the former U.S. Minerals Management Service (now reorganized as the Bureau of Ocean Energy Management) the Rigs-to-Reefs (RTR) program recycles retired rigs as artificial reefs with the aim of aiding marine communities and fisheries and saving the gas and oil industry significant money. Often a rig is dragged to a new location and then sunk to create an artificial reef. So far restricted to shallow waters, the first RTR conversion took place in 1979, off Florida’s coast and since then other programs have been put into place elsewhere around the globe, such as in Southeast Asia.
In a review article published in the October issue of Frontiers in Ecology and the Environment researchers Peter Macreadie, Ashley Fowler, and David Booth note the growing pressure to expand the RTR program to the deep seas, areas 500 meters or more in depth. Though relatively rare in the deep sea, natural reefs are increasingly threatened. And with more than 6,500 rigs due for retirement by 2025, the time seems ripe to consider creating deep-sea artificial reef complexes, say the authors.
“Thousands of massive oil rigs reaching the end of their production life all at once is unique to the present time,” explains Macreadie. “The newer rigs are very different to these ‘old school’ fixed-jacket style rigs; they don’t have anywhere near as much structure.”
Macreadie and colleagues highlight existing research on the consequences of rigs in shallow water to outline the potential benefits and detriments that retired rigs might offer deep-sea communities. For example, rigs might be especially helpful in protecting marine life against illegal trawling. The rigs’ large internal spaces could offer shelter to fish and other organisms, which could be especially beneficial to species that are long-lived, slow-growing, and slow to reproduce and therefore most vulnerable to overfishing. However, the authors note that while the crossbeams and large internal space of recycled rigs may be useful habitat for larger organisms, small fish and invertebrates would likely not find suitable habitat in rigs until coral and other encrusting species create a more hospitable environment.
Artificial reefs created by retired rigs could also offer “stepping stones” for animals to move between vast expanses of soft bottom sediment. Removing long-distance barriers could be good or bad, depending on the species, say the authors.
Other potential risks associated with rigs include smothering existing communities during placement of a rig, releasing contaminants such as hydrocarbons, and accidentally introducing invasive species that may be attached to rig surfaces.
A big hindrance to better knowing the potential pros and cons of bringing rigs to the deep-sea, say the authors, is a dearth of research. They propose that: “Partnerships between scientists and industry (e.g. The SERPENT project) will improve the capacity for further research, and we recommend that industry savings from a RTR program should support independent research and monitoring programs to evaluate the effectiveness of rigs in fulfilling their intended purpose as artificial reefs in the deep sea.”
Photo credits: Jellyfish and steel jacket photos, Shell; basket stars, Danial Jones and Andrew Gates