Aquaculture of giant kelp

Aquaculture of giant kelp, Macrocystis pyrifera, involves growing this seaweed for products like food, dietary supplements, and potash. The kelp itself is rich in iodine, potassium, other minerals, vitamins, and carbohydrates.

History

In the early 1900s, California’s kelp beds were harvested for potash. Interest grew again in the 1970s and 1980s for alginate production and as a biomass source for animal feed during the energy crisis, but commercial farming of M. pyrifera never took off.

When the energy crisis ended and alginate prices dropped, research into farming it slowed. During the early 1990s, supply for alginate relied on managing and restoring natural beds. In California, the “Kelp bed project” transplanted adult specimens 3 to 6 meters long to stabilize harbor substrates and boost biodiversity.

Twenty-first century

In the twenty-first century, research is looking at using the kelp as feed for farmed fish. China and Chile are the top producers of aquatic plants and algae, each making over 300,000 tonnes in 2007, though how much of that is M. pyrifera is unclear.

Chile’s production is split evenly between brown algae (Phaeophytes) and red algae (Rhodophytes), while China grows a wider variety including green algae (Chlorophytes). Chilean experiments are exploring hybrids of M. pyrifera and M. integrifolia. Kelp farming is also developing in Oregon and British Columbia, and startups have begun leasing water in Alaska for large-scale cultivation.

Northern California lost 95% of its kelp ecosystems in the 2010s due to marine heatwaves. Recovery efforts focus on removing sea urchins, either by scuba divers or by their natural predator, the sea otter. An invasive brown algae, Sargassum horneri, first spotted in 2003, is also a problem. Researchers at UC Davis’s Bodega Marine Laboratory are developing replanting strategies, and volunteers from the Orange County Coastkeeper group are replanting giant kelp.

Humboldt State University started cultivating bull kelp at its research farm in 2021. State-level research to prevent kelp forest collapse was announced in July 2020. At the federal level, the KELP Act (H.R. 4458), introduced in July 2021, would create a NOAA grant program for kelp forest restoration. Ocean Rainforest, a Faroe Islands company, received $4.5 million in U.S. government funding to grow giant kelp on an 86-acre farm off Santa Barbara, California.