Just beneath the waves along the Pacific Coast, from Alaska to Baja California, grow underwater forests that rival any on land. Kelp stalks can grow to 100 feet, forming a towering canopy of fronds. The structures support tiny invertebrates, fish, birds, and mammals, and help sustain fisheries and tourism.
Given the ecological and economic importance of these vast hidden habitats, scientists became alarmed 10 years ago when a mysterious disease and an unprecedented marine heat wave battered them, leaving behind only patches of surviving forest. Marine scientist and underwater photographer Kate Vylet has spent the past decade documenting the changes off the central California coast and the efforts of scientists and volunteers to preserve and restore the vibrant habitat. One of her photographs, “Of Blades & Spines,” won the 2023 Big Picture Grand Prize for Aquatic Life from the California Academy of Sciences.
Kelp in Good Health
Sunlight breaks through the canopy of a kelp forest. The fronds at the surface are dense enough to support the weight of egrets and herons as they spear fish hiding among the blades. Meanwhile, visitors like Brandt’s Cormorants (below) zip through to catch a bite. “They go blasting past you and come up with a fish,” Vylet says.
Snails and crabs graze on kelp, and the rocky seafloor is home to sponges, sea squirts, and other invertebrates. “There isn’t a single inch unoccupied,” Vylet says. For human divers and snorkelers lucky enough to visit, it’s like being in a terrestrial forest, she adds, with one key difference: “You’re flying through it rather than walking.”
Purple sea urchins are critical to a healthy kelp forest. The echinoderms use their sensitive tube feet to catch drifting kelp blades and pass them into their mouth (slide 2, below). Messy eaters, urchins break seaweed into smaller pieces, which other creatures consume.
In a thriving habitat, urchins hide from sunflower sea stars, their main predator, in rocky crevices. But a decade ago a perplexing wasting disease obliterated the stars; then historic underwater heat waves weakened cold-loving kelp. With the balance upset, urchins shed their shyness: They “went nuts,” says marine ecologist Mark Carr from the University of California, Santa Cruz. “They came out of cracks and crevices looking for things to eat.” They devoured living kelp, leaving behind desolate “urchin barrens” (slide 4, above), where few other creatures can survive.
The Rescue Effort
Communities up and down the Pacific Coast are working to restore the forests. Volunteers with Reef Check don scuba gear to survey biodiversity and kelp health (below). “Monitoring is key,” says Dan Abbott, who leads the kelp forest program at the California-based nonprofit. Other volunteer divers take a direct approach by smashing urchins with hammers (slide 4, below).
But the creatures shouldn’t be villainized, according to Vylet. “The invisible gears of climate change are shifting the ecosystem,” she says. “Urchins are responding and so is the kelp. Everything’s just trying to survive.”
Facing this reality, researchers in central California are increasingly focused on protecting healthy patches, where sea otters (slide 3, above) help keep urchins in check. Ultimately, Vylet says, saving kelp forests will require reducing carbon emissions as well as hands-on conservation: “Maybe we can help the kelp forest adapt to this new environment.”
This story originally ran in the Summer 2023 issue as “Kelp Forest Adrift.” To receive our print magazine, become a member by making a donation today.