Reef Restoration Project Offshore Southern California Brings Back Fish, Invertebrates, and Kelp Habitats

     The National Oceanic and Atmospheric Administration (NOAA) announced in December that its Palos Verdes Reef restoration project, completed four years ago, is now assessed to be a success as fish biomass increases by over 150%. The previous reefs and kelp forests were degraded and destroyed by landslides, chemicals like PCBs and DDT, and sewage. Marine habitat was degraded. Starting from scratch, an artificial reef was built. Workers, divers, and scientists emplaced 70,000 tons of rocks of different shapes and sizes to build the reef.

     In December 2020, after the artificial/restored reef had been completed for a few months, NOAA noted:

“Rocky reefs are known to be nurseries for younger fish to grow, and are much more productive than soft-bottom areas. The new reefs are already supporting a diversity of fish species. Additionally, the reefs ascend high enough off the seafloor that they’ll avoid being buried by landslides in the future—a win-win for the local marine ecosystem.”

“From May to September 2020, construction crews deposited quarry rock in 18 modules across more than 30 acres of seafloor. The design was a collaboration between the Vantuna Research Group and the Southern California Marine Science Institute. It mimicked the natural structure of successful reefs nearby, with a mix of heights, gaps, and channels to create hiding places and keep sediment moving. 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.”

     The project had four goals to ensure the reef functioned as a true habitat: 1) Increase the cover of marine life on the reef surface, 2) Boost the biomass of fish on the new reef, 3) Improve fish biomass across the broader 62-acre reef complex, and 4) Prevent invasive species from taking over.

     It appears that those goals have been met. The report for 2024, released in August 2025, documents the continued habitat improvements for fish, other aquatic organisms, and sea plants like kelp. The site is about 30 acres in size, with “halo” effects observed for about 30 meters beyond the reef in terms of fish and aquatic life. There are 18 mounds in the reef complex, with habitat for fish, invertebrates, algae, and kelp.

     According to Laurelle Stelle of The Cool Down:

“The project was so successful that it even uncovered an acre of natural reef nearby, adding even more to the healthy habitat restoration project, which was made possible only by the efforts of scientists and divers. There is now more than 11 times as much biomass as there was in the area, and despite concerns that invasive species would take advantage of the new habitat, that hasn't happened; instead, the desired native species are benefiting. All this took place in just four years, marking the project as an unreserved success.”

 

 

 

References:

 

A Restored Reef Brings Fish Habitat Back to Southern California. National Oceanic and Atmospheric Administration. NOAA Fisheries. December 8, 2025. A Restored Reef Brings Fish Habitat Back to Southern California | NOAA Fisheries

Officials celebrate completion of 70,000-ton project off US coast — here are the details. Laurelle Stelle. The Cool Down. January 10, 2026. Officials celebrate completion of 70,000-ton project off US coast — here are the details

Palos Verdes Reef Restoration Project Annual Report: Project Year 4 (2024). Southern California Marine Institute and Vantuna Research Group, Occidental College. August 2025.  PV Reef Project Year 4.pdf

More Than 30 Acres of New Reef Habitat Built Off the Southern California Coast. NOAA Fisheries. December 16, 2020. More Than 30 Acres of New Reef Habitat Built Off the Southern California Coast | NOAA Fisheries