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From grief to artificial Wheeler North Reef

When a natural kelp forest off San Onofre was decimated from years of harmful effects by the now-defunct San Onofre Nuclear Power Station, the plant’s main player, Southern California Edison, was called on to pay for a new, albeit artificial, reef as compensation. However, a nonnative reef isn’t natural. Would it function and survive like the original?

To begin at the beginning, the San Onofre reactors were built seaside to take advantage of the ocean’s cooling powers. Large intake pipes slurp up seawater, inadvertently carrying along sand also sucked up from the seafloor. As the slurry circulates to cool the scorching reactors, the seawater absorbs the heat, ratcheting up its own temperature by nearly 20 degrees. Before this bathwater can be returned to the ocean, it must mingle with ten additional times its volume of fresh seawater to re-chill it to the temperature of the ocean. Once done, the seawater-sand mixture is cycled back to the surrounding ocean. Repeat slurp, cycle, cool, flush, and repeat with 2 billion gallons per day of water-sand slurry across 30 years.

What’s the problem?

Who is Wheeler North?

Wheeler North (1922-2002) was a marine biology and environmental scientist at Scripps Institution of Oceanography and Caltech. He is best known for his pioneering work on the ecology of California’s coastal kelp forests. As a student of marine science (beginning in 1949), he was one of the first to use scuba diving in his research. Most long-time divers have a copy of his iconic marine life identification book, Underwater California (published in 1975), in their personal library.  

Sand in the released water is released as a dense, cloudy plume akin to constant sand storms on land. The drop in underwater visibility resulted in a loss of photosynthesis by marine algae due to a lack of light infiltrating the water. And silt settling on the kelp further blocks the ability of young kelp (Macrocystis pyrifera), especially, to photosynthesize. After decades of power plant plumes, the native kelp bed was permanently damaged. Consequently, in 1991, the California Coastal Commission required the power plant’s major player, Southern California Edison, to finance the building of a 176-acre offshore artificial kelp bed. Though small compared with natural kelp beds, so-named Wheeler North Reef is the largest artificial reef to date.

A kelp bed supports a village

Why invest human and financial resources to fix what is, relatively speaking, a tiny kelp bed? For one, it’s more than just kelp because a kelp bed evolves into a kelp forest. Consider forests on land. Plants on land and algae (which include kelp) in the ocean provide many of the same benefits. They are places that promote and sustain many different species. Wouldn’t it be cheaper and easier to sink an old ship or some other wreckage instead of getting mixed up in all this kelp restoration business? Historically, it is shown that wreckage offers a quick fix to attract fish but not a long-term solution.

A forest, however, hosted by giant kelp houses diverse species that find food, shelter, and a sort-of community center for reproductive activities. Even in death, disintegrating kelp adds nutrients to the surrounding water, elements that are otherwise scarce but essential for the growth and survival of other species. And sunken man-made scrap, on the other hand, is risky because it may be an environmental and maritime hazard as it decays.

A one-two punch

The question remains as to whether it is possible to re-create a kelp bed and see the bed evolve into a self-supporting, thriving forest full of life in perpetuity. This is no straightforward experiment since attempts to build artificial reefs elsewhere have failed, not surprisingly because little is known about the complex make-up of a natural kelp forest.

Stephen Schroeter, a biologist at the University of California, Santa Barbara, Marine Science Institute, along with ocean science collaborators, including Hany Elwany, a coastal engineer and oceanographer with Coastal Environments in La Jolla, have set out to try. Their goals have been to first build a reef that supports kelp and, second, continually monitor its growth and survival (including other understory algae, invertebrates, and fish) over time. It hasn’t been easy. They started with a 5-year experimental phase, during which time the team identified the best conditions for attracting and sustaining giant kelp and other reef-associated life.

I won’t keep you in suspense. After fits and starts (which began in 2004), where plots of rip-rap made of different materials were piled up at different heights on the seafloor, the winning entry for the best kelp growth (or growth at all) on Wheeler North Reef was low-relief concrete rubble or quarry rock. One big problem found on all the practice plots (to varying degrees) has been sea fans, those colorful, treelike colonial invertebrates that compete with giant kelp for rip-rap real estate. Scientists discovered that assembling the rubble too high above the seafloor invited the sea fans to settle before the giant kelp could get a holdfast in. But like in the story of The Three Bears, when everything is just right (rip-rap material, location, and height), fan settlement was reduced—if not deterred.

Something fishy

To date, there is much good news to report about Wheeler North but with caveats. One major goal, to sustain a giant kelp population, has happened. Other algae have settled as well, and the varieties of these small understory kelps are in tune with neighboring native kelp beds. Another success is the slew of invertebrate species, which have settled and reproduced. Reproduction is key because it shows that individuals from nearby native reefs are not just passing through but have moved in to stay. Yet when it comes to the “beef” of the reef—the fish populace—challenges remain.

Natural kelp forests serve as nurseries for many fish species so it is crucial for Wheeler North to behave as such. To date, the larger fish on the reef aren’t “home grown” to Wheeler North but are recruits from the nearest (natural) kelp bed. And since Wheeler North was built, fish populations in the nearby natural kelp bed haven’t bumped up their numbers. It is estimated that at Wheeler North, the tonnage of fish is half of what is typical in a flourishing kelp bed. Present thoughts are that the numbers won’t increase unless the reef’s footprint is enlarged.

Longstanding question

Can we sustainably replace this lost resource? Said Schroeter, “In the last 2 years of monitoring, we found that Wheeler North was similar to nearby reference [native] reefs.” Although it’s been 10 years in the making, that is short term for an artificial reef project. Right now, the reef looks excellent but any celebration must wait until multiple challenges are overcome. More studies must be carried out on the inscrutable sea fans to determine the most cost-effective means of managing and deterring these native, yet unwelcome, kelp pests because the sea fan puzzle connects to weather.

Storms result in kelp being torn off the reef, which opens the door for the dogged sea fans to establish an empire or at least family estates. Inclement weather also affects sand movement, specifically how fast and how much sand covers the rip-rap. Studies show that if more than ten percent of the rip-rap is buried, the kelp bed won’t survive. Thus, this project is much more than a mitigation project. Victories and pitfalls experienced here add to the fragile body of knowledge of what goes into making and sustaining a kelp forest, at least an artificial one.

Continual monitoring crucial

“Understanding what makes a kelp bed stable and viable over the long term may determine whether a reef can truly be replaced if lost.”

People too often assume that scientists can fix any human-made mess but not necessarily and, even if so, the fix could be cost prohibitive. According to Elwany, “A successful artificial reef is easy and cheap, certainly next to the $100 million spent on restoration projects like for the San Elijo Lagoon in North San Diego County.” That’s good news but can an artificial reef be enduringly self-sustaining or will it always require periodic intervention?

Said Schroeter. “Understanding what makes a kelp bed stable and viable over the long term may determine whether a reef can truly be replaced if lost.” The best one can do is continually monitor and learn how to best tweak the system to keep it functioning. In other words, we can’t just “plant” the reef and leave it to its own devices. Continual direct monitoring of the reef by scuba divers is the only way to take the pulse of the reef. They know early on when intervention is needed and can take immediate and effective action.

Imagine spending a big chunk of money hiring a landscape architect, purchasing expensive starter flora, planting, and watering for a few weeks, then walking away from the project and expecting it to thrive. This is why it is problematic that monitoring of Wheeler North by divers is only carried out May through October. What happens to the reef in between this time is anyone’s guess. Stormy winter months are most precarious in terms of water movement and kelp upheaval. Even when storms are thousands of miles away, they bring swells and potential damage, even when we are enjoying warm, dry weather.

Why be pennywise and pound foolish? It makes more than cents to institute monitoring year round. Right now, Wheeler North has a good chance of compensating for the loss of kelp forest life sustained by the power plant’s activities and being the first artificial reef to claim success. Each year’s monitoring (if continually funded) will add yet a new chapter in the story and study of Wheeler North Reef.

Author’s note: Since, dear readers, I’ve experienced over three decades of diving natural kelp forests, you may wonder about my experience on Wheeler North. I can only wonder, too, because I was, then wasn’t, provided an opportunity to get out there and see for myself. Hence, this article, while informational, lacks images and personal synthesis. Maybe in the future….

A brief history of Southern California artificial reefs

While artificial reefs have been around for over 200 years, the California Department of Fish & Game created Southern California’s first artificial reefs in 1958. The objective was to maintain sportfishing in the face of increasing fishing pressure and its destruction of nearshore habitats. Over the decades, various junk were sunk (like old cars, concrete, wooden streetcars, ships) in different areas off the coast. While they made for efficient killing stations, they not only did not help maintain or increase fish populations, overall catch and fish populations decreased. This is because dumped junk isn’t a complex ecosystem like a kelp forest. A kelp bed targets keystone animal species, those that sit at the foundation of a healthy, productive reef and attract myriad other species. Divers who descend onto the sunken ships in Wreck Ally off of Mission Bay see masses of single anemone species and gorgonians, animals that take advantage of a crooked system by settling quickly and out-competing giant kelp spores. Make no mistake, dumping junk also pollutes because no matter the extent of precleaning, the large debris degrade in ways that we are unaware.

— Judith Lea Garfield, naturalist and underwater photographer, has authored two natural history books about the underwater park off La Jolla Cove and La Jolla Shores. Send comments to