Community Coastal Column: The State of Kelp Forests on the North coast

A curious harbor seal eyes the camera in a South Laguna giant kelp forest.
Photo credit: Alex Cowdell, California Sea Grant Flikr.

I was lucky to grow up on the Monterey Bay, where the kelp forest is a legendary and beloved ecosystem. From early childhood through college, many school field trips and science projects focused on the intricate web of life nestled among the golden fronds of giant kelp (Macrocystis pyrifera). When I moved to the North Coast, I wondered about the structure and condition of our local kelp beds, which are dominated by bull kelp (Nereocystis luetkeana). Last month’s Coastal Column discussed this species and gave a general overview of the evolution and characteristics of kelp and seaweed. This month, I’d like to talk about some of the traits of a kelp forest and what we know about the current state of kelp on the Northcoast.

The key players in a kelp forest ecosystem are species you may recognize: sea otters, sunflower sea stars, purple urchins, abalone, and many more. Kelp serves as both a habitat and a food source by sheltering young fish amongst its waving fronds and giving herbivorous creatures something to graze on. Like land plants, kelp is a primary producer that turns sunlight into energy. This ability puts kelp at the bottom of the food chain, providing the energy to power all the other species in the ecosystem. Grazers like red abalone and especially purple sea urchin like to nibble on the kelp’s holdfast — the root-like structure that keeps the kelp anchored to the rock. Those grazers are a favorite treat for key predators like sea otters and sunflower sea stars, who help maintain the ecosystem balance by keeping their populations in check.

One of the biggest problems facing kelp forests is the disappearance of these key predators. Sea otters were eradicated from the Northcoast by the early 1900s due to the insatiable demand for their thick pelts. A wandering male will occasionally make its way to our area, but no stable population exists between Washington and Monterey Bay. Now, the job of keeping the ecosystem in balance falls to sunflower sea stars. These many-armed echinoderms are the second-largest species of sea star on the planet, and can grow an arm span up to one meter. Their huge size means that they have no problem gobbling up creatures like snails, clams, and urchins. Unfortunately, these predators are also facing dire times. Starting in 2013, a wave of Sea Star Wasting Syndrome devastated populations of sea stars all along the Pacific coast, and their numbers haven’t fully recovered. Without the predation pressures of sunflower stars and sea otters, purple urchins can carpet the underwater landscape and prevent new kelp from growing. Compounding these problems is the issue of warming waters, which provide fewer nutrients to cold-loving kelp. With all these challenges stacking up, it’s hard to see a happy future for Northern California’s kelp beds. But recent developments have inspired some measure of hope among kelp lovers.

In the last two years, areas where kelp forests had almost completely disappeared are seeing a comeback. A recent article in Bay Nature by Alastair Bland describes the surprising regrowth of kelp beds in Mendocino and Sonoma counties, despite the overpopulation of purple urchins. This phenomenon challenges the assumption that kelp beds cannot recover once urchins have taken over, but further research is needed to determine exactly how this happened. This is great news for struggling kelp ecosystems south of Humboldt county, but what about our local kelp beds in Trinidad and Crescent City? Unfortunately, there’s much less data for these areas. But the data we do have show that while our kelp beds are less extensive than those to the south, they have remained remarkably strong despite the warm waters and predator eradication that have spelled disaster for much of the rest of California. While researchers study this phenomenon, everyday people on the Northcoast can show their love for kelp by visiting the kelp beds in places like Trinidad Bay and supporting initiatives to restore and protect them.

If you or someone you know is passionate about kelp ecosystem health or have knowledge to share, please feel free to reach out to me at ivynecmail@gmail.com.

For more information, check out Kelp Forests Surge Back on Parts of the North Coast, with a Lesson About Environmental Stability by Alastair Bland for Bay Nature; ‘Critical Juncture’
A Race Against Time to Save the North Coast’s Bull Kelp Forests by Kimberly Wear for the North Coast Journal; and Sea Star Wasting Syndrome from www.marine.ucsc.edu.