Are Storms Good for Kelp Forests?
By: Deidre Sullivan, Co-Principal Investigator of the CIMI Kelp Restoration Project
The extremely devastating January 2025 fires in Los Angeles will not soon be forgotten. I watched my high school burn in the Pacific Palisades on TV and felt for so many who have lost their homes and businesses. Those same fierce winds, which fueled the flames, also forced us to delay our winter kelp monitoring.
As we waited, we wondered …
How would these powerful winds and waves impact the young kelp that had only recently taken hold at our study sites?
Observing the Aftermath
Giant Kelp washed ashore after the storm.
Once the winds subsided, we headed to the beach to assess the damage. Seeing dislodged kelp washed up on the shore raised some early concerns. However, when we dived into the water, we were relieved to find the scene was far from a disaster.
Instead, it looked as if the ocean had given the underwater landscape a deep clean. The cobbles were swept spotless, the larger boulders remained in place, and the kelp, though slightly tattered, appeared surprisingly refreshed.
One of the most striking observations was the significant reduction in Sargassum horneri, the invasive algae that often competes with kelp, as well as a decrease in native turf algae, another key competitor.
We also observed a nearly 20% reduction in kelp plants compared to our November kelp census. Some kelp had shifted locations, while others remained anchored to boulders that had been overturned. The greatest losses occurred on cobble-sized rocks, ranging from baseball to bowling ball size. In shallower areas, rocks were even cleaner, with tumbling during the storm stripping them bare.
Resilience and Recovery
Amid this natural chaos, I gained a newfound respect for green abalone. Since the harvesting of abalone was banned in 1997, their populations have recovered well in Catalina. In the “surf zone”, I noticed large green abalones with patches of mother-of-pearl exposed on the outside of their shells—a testament to the storms they had endured, surviving relentless battering from cobbles and boulders.
Reflecting on the conditions that allowed kelp to return after a nine-year absence in 2023, I realized they were the very conditions created by the recent storm:
Removal of Overgrowth: The storm cleared turf algae and invasive Sargassum, opening up new "real estate" for kelp spores to settle.
Over-turning Rocks: The storm tumbled many rocks, especially in the shallow areas, again opening up additional "real estate" for kelp spores to settle.
Water Motion for Spore Dispersal: The storm’s water movement likely carried spores and/or entire plants dislodged from kelp forests miles away.
Cooler, Nutrient-Rich Water: Storms stir the water column, bringing nutrient-rich deeper water to the surface, ideal for kelp growth.
The Fine Line Between Beneficial and Destructive
Storms can be devastating when they’re too intense. In August 2014, a hurricane off Mexico generated massive swells that devastated Catalina Island’s kelp forests. This destruction coincided with an unprecedented marine heatwave and a severe El Niño, which hindered kelp recovery. Without the kelp, Sargassum and native turf algae flourished, capitalizing on the increased light from the cleared canopies.
A Helpful Winter Cleaning
The Santa Ana winds that swept through Los Angeles this January will long be remembered. For our study sites, however, they provided an unexpected "winter cleaning," creating space for kelp spores to settle at just the right time of year. Nature’s balance is delicate, and while storms can cause destruction, they also play a vital role in rejuvenating and maintaining the health of kelp forests.