Help the kelp! Community science project seeks divers

Northern California is known across the globe for its towering redwood forests. Home to the largest known living tree, Hyperion, at 380 ft. tall, there is no question that this corner of the world has impressive natural habitats. In the shadows of these giants, however, lies a different type of forest, equally as impressive as the soaring sequoias—but hidden under the ocean surface.

While there are no billboards and gift shops off the main highway heralding their beauty, kelp forests are an essential part of northern California communities, and hotspots of marine biodiversity. Growing along cool, rocky shores, the “trees” of this forest are a species of brown alga called bull kelp. Kelp forests and their inhabitants have sustained human populations for… well, ever. Indigenous peoples have relied on kelp forests for food and ceremony since time immemorial. And in just the last few decades, abalone diving has grown into a multi-million dollar industry on the north coast. That’s why it was such a shock when the forests disappeared.

Starting in 2013, a series of stressful oceanographic and ecological phenomena has destroyed bull kelp populations. First, warm waters killed existing bull kelp, then an epidemic (sea star wasting syndrome) killed the predators that normally keep kelp-eaters in check. Now these herbivores, especially purple sea urchins, roam freely and devour any kelp plants that sprout up, preventing the recovery of the habitat-forming species.

Communities respond to kelp forest devastation

Needless to say, community members are deeply concerned. While rigorous scientific experiments are underway to determine the best kelp restoration strategies, local scuba divers are eager to help. To leverage the power of the masses, as the California Sea Grant Kelp Management Extension Fellow I am helping to lead a community science project using volunteer divers to cull purple sea urchins in one monitored location: Caspar Cove in Mendocino County.

The purpose of this project is to investigate whether in-water purple urchin culling by volunteer divers can support kelp regrowth. Results will help managers determine whether this can be a useful kelp restoration tool more broadly. In this project, we’re collaborating with The Waterman’s Alliance, CDFW, the Ocean Protection Council, and Reef Check California.

Get involved

To participate, divers must have a valid recreational fishing license and scuba certifications. You can use hand tools to cull subtidal purple sea urchins on the south side of Caspar Cove (areas A–C in the map). Record details about your dive including how many urchins you culled using this form: Caspar Cove Dive Log. Results are automatically updated every 5 minutes on the Caspar Cove Dive Log Data page. 

We are thankful to have such a supportive community and excited to get recreational divers involved in solutions for kelp forest recovery!