LONG BEACH - What's to be done with California's offshore oil rigs once they have outlived their usefulness?
One option: Remove them entirely from the ocean floor and restore the marine environment to its original state, as is California's current policy.
But marine biologists at Cal State Long Beach say it might make more environmental sense to actually leave at least some of each defunct oil rig intact.
Although originally foreign to the marine environment, since their installation, the oil platforms have been co-opted by species of fish who have made the rigs their habitat, even preferring it in some cases to a natural reef, according to Chris Lowe, a CSULB marine biology professor.
"It's basically like a high-rise building for fish, and each level actually provides another level of sea-floor habitat," he said.
Lowe and marine biology graduate students have conducted three studies of oil platforms in the Santa Barbara Channel and off the coast of Huntington Beach and Long Beach.
Why do some fish flourish on oil rigs? Because the oil rigs extend to the sea floor, they can serve fish that prefer living in the deepest parts of the ocean, as well as those who like hanging out in mid-depth or shallow parts, Lowe said.
In addition, over time, the platforms have become covered with scallops and other invertebrates that serve as food for many of the species, he added.
Also helping: Fishing is banned near offshore rigs, creating a de facto protected marine habitat for the platform dwellers. As a result, many fish call the oil rig their long-term home, according to research by Lowe and graduate student Carlos Mireles.
Santa Barbara oil platforms draw a lot of rockfish and lingcod, which are important for recreational and commercial fishing, Lowe said. Rockfish populations have been overfished, he added.
The seven oil platforms off Long Beach and Huntington Beach draw a different mix: California sheephead, bass, surfperches and other species, according to research by Lowe and graduate student Chris Martin.
There is an important problem with completely removing California's defunct oil rigs, many of which are more than 25 years old, Lowe said.
Doing so involves detonating underwater charges to uproot the rig's base from the ocean floor, Lowe said. Those sorts of explosions would "kill everything around the platform," he added.
One alternative would be to catch and relocate the fish to protected marine habitats before destroying the platforms, Lowe said. But would the fish stay in their new environment, or would they decide to swim back to the oil rig, where they could again be subject to a deadly, rig-removing explosion?
In a study by Lowe and graduate student Kim Anthony, researchers took some fish from a Santa Barbara oil platform and relocated them to a protected marine habitat at Anacapa Island, part of the Channel Islands archipelago.
After tracking the fish for two years, only 25 percent had returned to the platform.
The problem with relocation plans is that they require a year of intense fishing before the oil rig is decommissioned, he said.
"It would probably work, but it would be very expensive," Lowe said.
Another alternative: Keep the oil rigs where they are after the wells are capped and rendered defunct.
The rigs can be kept completely intact or only partially removed - perhaps cut off at a depth of 85 feet - to leave undisturbed the habitats that have formed at the rigs, he said.
California policy currently calls for oil companies to decommission, uproot and totally remove oil platforms - a very expensive process, Lowe said.
According to a 2004 estimate, totally removing Long Beach's offshore oil platforms would cost oil companies $250million for each rig, Lowe said.
Another option for California is to mimic Gulf states that have allowed oil companies to leave defunct offshore rigs for use as marine habitats.
As part of the deal, the oil companies give the Gulf states a portion of the savings achieved by avoiding a complete, costly removal of the oil rigs, Lowe said. That money can then support the states' environmental efforts.
The studies were funded by grants from the U.S. Minerals Management Service, the California Artificial Reef Enhancement Program, a USC Sea Grant and the California Ocean Protection Council.