On a sunny afternoon in mid-April, Professor Eric Sanford crouched in a tide pool off Bodega Bay and turned over algae-covered rocks in search of a chocolate porcelain crab, a dime-size crustacean with blue speckles.

The creature has been spotted in small numbers around Bodega Bay for decades. But five years ago a severe marine heat wave, dubbed “the blob,” caused a sharp increase in its numbers north of the Golden Gate, says Sanford, a marine ecologist who researches climate change and coastal ecosystems at UC Davis’ Bodega Marine Lab.

“I look at how organisms adapt to climate change,” says Sanford, who regularly publishes articles in scientific journals on how life between the Northern California tides is changing. “We’re now seeing chocolate porcelain crabs and dozens of other species migrating north.”

Northern California’s rugged coast, thick fog and nutrient-rich waters have created one of the most diverse ecosystems on the planet. The state’s intertidal zone — the 9-foot-wide band of coast between the highest of high tides and the lowest of low tides — is home to an intricate web of marine life that evolved over millions of years but remained largely static since that last Ice Age — until recently.

From the southern tip of Baja California to southeast Alaska, the range of sea creatures has pushed northward as water has warmed. Some creatures are expanding their range as they migrate north by holding on to their southern frontier. Others are disappearing from their historical homes.

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