Reef Restoration Off Palos Verdes Paying Off In Ways ‘Scientists Didn’t Fully Expect’

PALOS VERDES, CA — Miles below the ocean’s surface off the coast of the Palos Verdes Peninsula, a striking change is underway — one that is rooted in the efforts of a reef restoration project, wildlife officials announced last week.

Four years after its construction, the project is “paying off in ways that even the scientists didn’t fully expect,” the National Oceanic and Atmospheric Administration said.

Since the project’s creation, the fish biomass — “the total weight of living organisms” — has increased by 150%, officials said.

“The thousands of fish darting around the Palos Verdes Reef, invertebrates hiding in its crevices, and marine mammals foraging through the flowing kelp forests were unthinkable sights just a few short years ago,” officials said. “This transformation, from a barren sea floor to a habitat teeming with life, isn’t just a local success story. It’s a demonstration of how habitat restoration can bring marine ecosystems back to life.”

Why Healthy Reefs Matter

The health of a reef affects the survival of many species, according to officials.

“From small forage fish to larger predators, rocky reefs support species that feed seabirds, harbor seals, and humans,” officials said. “Hard surfaces give kelp and algae a place to anchor, which in turn creates shelter and food for fish and invertebrates.”

Specifically, of the Palos Verdes coast, a variety of species, including kelp bass, barred sand bass, sheephead, and California spiny lobster, are important for both commercial and recreational fishing, officials said.

However, in the mid-20th century, sewage outfall and landslides stripped the Palos Verdes shelf of its kelp forest, according to officials.

“By the 1960s, giant kelp—once so abundant it created a canopy visible from shore—had all but disappeared,” officials said.

While restoration efforts helped bring kelp back to some areas, officials said “many natural reefs remained smothered under shifting sediment.”

“They were also heavily impacted by the lingering effects of DDT and PCB contamination,” according to officials.

After NOAA and other federal and state agencies settled with the responsible parties in 2001, officials said, “the Montrose Settlements Restoration Program was established to restore the natural resources harmed by the chemicals, including fishing and fish habitat.”

The Restoration Project

The Palos Verdes Reef project is one among nearly 20 restoration efforts funded from the settlement, officials said.

Years of study and community input went into the reef’s design, aimed at restoring “an area impacted by historical chemical pollution” to help the reef’s inhabitants, according to officials.

Over the course of four months in 2020, officials said “construction crews deposited quarry rock in 18 modules across more than 30 acres of seafloor.”

More than 70,000 tons of rock were lowered to the ocean floor “in carefully engineered mounds,” officials said.

The design, a collaboration between the Vantuna Research Group and the Southern California Marine Science Institute, “mimicked the natural structure of successful reefs nearby, with a mix of heights, gaps, and channels to create hiding places and keep sediment moving,” officials said.

“The new reefs were also built high enough to avoid being re-buried by future landslides and keep fish away from the polluted sediment below.”

A Thriving Reef

An August report detailing the reef’s 2024 monitoring efforts “shows striking results,” officials said.

Compared to pre-construction levels, officials said, the biomass has increased by 1,178 percent, while the fish biomass specifically has increased by 166 percent — a sign that “the fish are thriving.”

The habitat is also expanding, officials said.

“Not only are fish using the new structures, but sediment has also shifted to reveal an acre of long-buried natural reef nearby, effectively increasing the habitat footprint,” officials said.

Though there were fears that invasive algae or invertebrates would colonize the new structure, none were detected, officials said.

“Instead, native kelp, coralline algae, and invertebrates are making use of the reef,” officials said.

Not only did biomass increase within the reef, but it also “more than doubled in the 30 meters that surround the reef—called ‘halo zones’—as compared to pre-construction numbers,” according to officials.