Bull Kelp Crisis: Why This Vital Marine Algae Is in Danger and How We Can Save It

Bull kelp (Nereocystis luetkeana) is a fast-growing marine algae that thrives in cold, temperate ocean waters along the Northeastern Pacific. Despite its ecological importance, this species has not yet been assessed by the IUCN Red List. However, state agencies, NOAA, nongovernmental organizations, and underwater survey groups like ReefCheck classify bull kelp as highly vulnerable, particularly in Northern California, Oregon, and the Salish Sea (Washington State and Canada).

What Is Bull Kelp?

Bull kelp is an annual species of marine algae that can grow up to 60 feet in a single season, accumulating biomass through photosynthesis faster than most other organisms on Earth. Its structure includes:

• A small holdfast that anchors it to rocky ocean floors.
• A long, singular stipe (stem) ending in a gas-filled bladder.
• A profusion of golden blades that extend toward the ocean surface.

This species typically inhabits nearshore waters up to 60 feet deep, where sunlight reaches the ocean floor and nutrients are readily available. Bull kelp begins its growth cycle in early spring, and by mid-summer, mature plants produce spores in specialized patches called sori. These spores eventually detach and settle on the ocean floor, restarting the cycle.

Mural Celebrating Bull Kelp

A striking mural by artist Josie Iselin is being used by the Northwest Straits Commission in Washington State to commemorate Bull Kelp Day on April 16th.

Where Is Bull Kelp Found?

Bull kelp grows along the Northeastern edge of the Pacific Ocean, where it meets the North American continent. Its range extends from Central California northward through:

• Oregon
• Washington
• British Columbia
• Southeast Alaska
• The Aleutian Islands (southwest Alaska, beyond Kodiak).

Bull kelp forests typically thrive within a few hundred yards of the coastline, relying on spring upwelling—a process that brings nutrient-rich waters from the deep ocean to the surface.

Why Is Bull Kelp at Risk?

A series of oceanic events has led to the collapse of bull kelp forests in Northern California and Oregon, while historic kelp beds in Puget Sound and the Salish Sea have also vanished. The primary threats include:

• Warming ocean temperatures, which trigger a decline in kelp health.
• Sea star wasting disease, which has decimated sea star populations—the top predators of sea urchins.
• Sea urchin overpopulation, which grazes down kelp forests, transforming biodiverse ecosystems into urchin barrens—barren wastelands on the ocean floor.
• The giant kelp (Macrocytis pyrifera) of Southern California faces similar risks from warming events.

These changes have devastating consequences for marine life, including rockfish, juvenile salmon, prey fish for birds, abalone, and countless other organisms that depend on kelp forests for habitat and food.

Who Is Working to Save Bull Kelp?

A coalition of organizations, agencies, Tribes, First Nations, and volunteers is actively working to restore and protect bull kelp populations. Key efforts include:

• NOAA marine sanctuary scientists.
• California and Oregon state agencies.
• Tribes and First Nations, including those in the Salish Sea region.
• Parks Canada.
• The Nature Conservancy.
• Puget Sound Restoration Fund.
• Northwest Straits Commission.
• Volunteers collecting purple sea urchins on weekends along the Northern California Coast.