Underwater Downtown Thrives off San Clemente Coast

Before 2008, the area south of was a relatively barren ocean bed under 30 to 40 feet of water.

Now, 174 acres of imported stone has knit together with patches of natural reef to create a 400-acre underwater expanse packed with sea life, creating what one UC Santa Barbara researcher says is likely the largest man-made kelp reef on the planet.

Scientists with Southern California Edison and UC Santa Barbara who monitor the reef say the artificial ecosystem has been an unprecedented success.

They credit careful planning and a series of cold, stormy years that created ideal kelp-growing conditions.

So far, the Wheeler North Reef is ahead of schedule in 10 of 14 criteria used to measure success. It's still falling short on the number and diversity of invertebrates, but many of those are rare species that "take a while to recruit," said Steve Schroeter of the UC Santa Barbara Marine Sciences Institute.

The reef is also meant to produce 28 tons of fish, but scientists observed only 16 tons of fish over the past season, according to UC Santa Barbara.

But, overall, the young kelp bed not only created a swath of biodiversity where there was little before—an accomplishment important in its own right—it also offers a laboratory for biologists to study reef development and the behavior of species that inhabit it.

“Speaking as a biologist, the awesome thing about these projects is they’re going to be going on long after we’re gone—long after I’m gone, long after the [San Onofre nuclear] plant is gone, long after my kids are gone,” said Pat Tennant, a marine biologist with Southern California Edison.

Creating the Reef

Just three years ago, the sprawling Wheeler North Kelp Reef was 120,000 tons of rock in a Catalina Island quarry.

The California Coastal Commission required Southern California Edison to build the $46-million reef to offset side effects from the San Onofre Nuclear Generating Station. The discharge of cooling water from the plant churned up sediment, blocking sunlight from the existing San Onofre Kelp Reef, killing off parts of it, UCSB's Schroeter said. 

The process to design the Wheeler North Kelp Reef started in the late 1970s, Tennant said. By the 1990s, scientists had developed a series of square patches off the coast, each with a different arrangement and type of stone substrate. Scientists used the experimental reef patches to gauge the most effective way to build a rocky base when it came time to create the main body of the project.

The total area of the test modules is 22 acres.

“The funny thing about artificial reefs is that very few people have got them right,” Tennant said. “If you put hard structures out in the water, it’s a magnet for fish. [But] we wanted to have a completely self-sustaining ecosystem.”

One key to the success of Wheeler North, Schroeter said, is that it’s a “low-relief” reef, meaning the boulder material rises only a few feet off the ocean floor, more closely mimicking the beds of naturally occurring kelp forests, such as the San Onofre bed.

To get those boulders there, Tennant said, SoCal Edison hired huge barges with elaborate derrick systems—the kind of equipment usually used to build jetties and breakwaters—to haul the stone from the Catalina Island quarry.

The barges were guided on where to dump the rocks by GPS, achieving accuracy to within about 3 feet. Pilots positioned the craft in preparation for the dump using a series of six anchors, Tennant said, at which point bulldozers on board shoved the stone over the side.

Progress and Monitoring

Schroeter, who runs the independent team of UC Santa Barbara scientists monitoring the reef, said it has been a big success. Usually, artificial reefs attract ocean life but are only minimally successful at creating ecosystems similar to natural reefs.

Many times, invertebrates such as sea fans take over, or the shelter of the rock substrate attracts plant-eating fish that gobble up kelp before it has a chance to grow.

“It’s unusual in that it’s doing really well for kelp, and it was designed to grow kelp,” Schroeter said. “Kelp generally tends not to do well on these man-made reefs.”

To keep watch on this underwater downtown, “I have a crew of eight divers who go out from around May to as late as October, and they sample four to five days a week in these kelp beds,” Schroeter said.

There are 92 fixed spots on the Wheeler North Reef—20 meters long by 5 meters wide—in which divers count every creature, recording the number and type of species, among other data.

The biologists also monitor the San Mateo Reef and Barn Reef about 6 miles south of the nuclear plant, Schroeter said.

Editor's note: Look for a photo feature this fall when Patch plans to send our diving-certified contributing photographer out with her underwater camera rig to shoot the UC Santa Barbara researchers conducting their studies.