Bird’s-eye view of a forest of giant kelp

This aerial view shows California’s Carmel Bay, near Point Lobos State Natural Reserve. The rocky reefs, kelp forests and dramatic granite pinnacles in these protected waters are home to abundant fish and invertebrate species—and offer some of the finest scuba diving in California.

Under the kelp canopy

Blue rockfish swim underneath a healthy forest canopy of giant kelp plants in the North Monastery region of Carmel Bay, just south of Monterey Bay off the coast of California. Kelp forests farther north have been largely denuded by grazing sea urchins. Underwater photographer Brandon Cole, ”My sincere hope is that the tide turns soon to spare the Monterey Peninsula kelp the same widespread devastation experienced farther up the California coast.”

Bull kelp

A blue rockfish swims past the air-filled bladders of bull kelp of the California coast. These air-filled bladders, called pneumatocysts, buoy up the stalks and blades of this fast-growing marine algae.

Red abalone surrounded by purple sea urchins

Red abalone—a highly prized sea snail—and sea urchins eat kelp and algae. In recent years, urchin numbers have soared, and the spiny invertebrates have devoured kelp and algae, causing abalone numbers to plummet.

Giant sunflower sea star

This giant sunflower sea star clings to a colorful rocky reef on the Monterey Peninsula in the early 2000s. Once abundant, this species has been especially hard hit by a sea-star wasting disease. Detected in 2013, the disease caused population losses of more than 90 percent in some areas. Sea stars are the main predator of sea urchins, so the loss of this key species from kelp forests in northern and central California has contributed to the explosion of the spiny invertebrates.

Survey of marine life in a kelp forest in Monterey Bay

Reef Check California’s Maxwell Seale conducts a survey of marine life in a kelp forest on a rocky reef in Monterey Bay. Here, purple sea urchins are feeding on bull kelp, clustered together on the holdfasts, the plant’s base, which anchors kelp to rocks. When urchins wipe out kelp and other algae, they leave behind a denuded substrate called “urchin barrens.” Many kelp forests in central and northern California have been decimated, significantly altering the ecosystem.

Lover's Cove in Monterey Bay

Once home to a thick kelp forest that harbored a diverse population of fish and invertebrates, Lover’s Cove is now an urchin barren. Yet as sea urchins raze giant kelp and bottom algae and create a bleak scene of rock and sand, they too suffer nutritionally. Some urchins die, leaving behind white skeletons called “tests.” Most enter a near-dormant state where they can survive without eating for years.

Dead sea star with wasting disease

This dead sea star, likely a Stimpson’s sun star, has died from wasting disease. This disease has affected more than 20 species of sea stars in the northeast Pacific Ocean, causing significant mortality and impacting entire ecosystems. The exact causes of the disease are still not entirely understood, though a virus appears to be at least partially responsible. The affliction causes lesions to develop and spread through the animal’s body.

Purple sea urchin with wasting disease

Afflicted with wasting disease, the spines of this purple sea urchin are falling off. When urchin populations explode in the absence of abundant predators such as sea stars, they raze kelp and algae, creating urchin barrens where there is little left to consume. The wasting disease is likely tied to stressors that include high urchin densities, poor nutrition, warming waters and poor water quality.