Scientists have known for years that the reefs created by shipwrecks and deep-sea oil rigs were acting like Hyatts and Sheratons for marine life in the world's shallow waters – but a recent study may indicate that these artificial structures may be hosting more diverse sea life in deeper water than previously thought.
The findings confirm that oil and gas platforms, as well as the wrecks themselves, are serving as hard surfaces, supporting hundreds of life forms.
The study, funded by Mineral Management Service (MMS) and National Oceanic and Atmospheric Administration (NOAA), revealed that as petroleum exploration and production expands into these deeper Gulf of Mexico waters, platforms in all depths of water were increasingly providing habitats for marine life.
The collaboration, a first of its kind, garnered the two organizations the Department of Interior's Cooperative Conservation Award and the NOAA's own Excellence in Parterning Award.
"By studying the artificial reef effects of World War II shipwrecks, this research may help us determine the potential effects of deep-sea drilling structures on biological communities," said Lars Herbst, acting regional director of MMS Gulf of Mexico OCS Region.
Specifically, the study investigated seven shipwrecks – including a German U-2 submarine – that lay in water ranging from 400 to 6,500 feet.
Herb Leedy, supervisor of the Biological Sciences Unit in the MMS Gulf of Mexico Region's Office of Leasing and Environment and one of the project’s lead scientists, said, "This study looked at the ecology of artificial substrates in water depths from about 300 feet to over 6,500 feet. We specifically looked at ships sunk within a few months of each other from 1941 to 1942."
Leedy says that conventional artificial reefs have been established in more shallow water, less than 300 feet, which is where previous studies have concentrated.
"So this really is a new frontier in artificial reef science," he says, specifically pointing to a clear reef effect at all sites down to 1,800 feet.
Saying the influence of the shipwrecks was evident at all depths in the kinds and numbers of epifaunal invertebrates associated with hard substrate and that the habitats formed almost immediately, Leedy concluded, "While the reef fish assemblages did not occur at the three deepest reef sites, the study showed that invertebrate species richness (number of species) and abundance of organisms was higher near the shipwrecks in comparison to away from the shipwrecks at all sites and depths."
In other words, fish were less common and less diverse at greater depths, indicating that marine life is attracted to the upper levels of rigs.
Scientists also discovered that wrecks at the intermediate depths had 50 percent more species than those in shallow or deeper water. This is explained by the turbidity in the lower depths and the extreme conditions of cold, darkness and pressure in the deeper regions.
The state of decay of these wrecks has little effect on the state of the reef, Leedy said: "There did not appear to be any effect from contamination."
What is clear, though, is that these wrecks provide an attractive habitat for many kinds of marine life.
"For fish, diversity generally decreased with depth,” Leedy said. “This trend was expected prior to the study. However, one surprise was the observation of large numbers of reef-associated fishes at the Gulf Penn in 1,800 feet of water.”
The fish documented there “are characteristic of deepwater hardbottom areas,” he said, “such as Lophelia reefs, located at similar depths in the north Atlantic."
What this means for the industry is also as murky as the deep waters. Leedy doesn't expect, for instance, industry to start redesigning platforms to accommodate the new sea life – but he believes some tweaking might occur.
"In water depths deeper than 400 feet, industry would likely opt for a tension leg platform or floating SPAR,” he said. “Currently, there are 40 to 50 fixed leg platforms in the Gulf of Mexico between 400 and 1,200 feet deep and a few more offshore California."
More importantly than what industry builds, Leedy says, the new findings many change what industry takes down.
"The results of this study will help agencies and industry make informed decisions during the decommissioning process."
Specifically, he says, that rigs to reef is a benefit to the environment, to the state sponsoring the reef site, and to the oil and gas industry. The sponsoring state and the donating oil company share the cost savings realized from reefing the structure.
"For instance, if it would cost a company $2 million to decommission a platform, but only $1 million to reef the structure in place, the company would donate $500,000 to the state’s artificial reef program."
All in all, this is good news for marine life. At shallow, intermediate and deep water, these rigs and shipwrecks are providing reef fishes, coral, and other marine life with comfortable accommodations – as any good hotel should.