How CA got its unique coastline, what cool creatures live there

Written by Danielle Chiriguayo, produced by Sarah Sweeney

Surfgrass (Phyllospadix) drapes over the rocky intertidal zone in Laguna Beach. Credit: University of Washington Press.

The California coast spans 840 miles and boasts all kinds of flora and fauna, including gooseneck barnacles that resemble miniature geese, water birds with names like bufflehead, and a fluorescent-colored sea slug called Spanish shawl. For decades, marine biologist Patrick Krug has explored the vastly biodiverse state. He’s a professor of biological sciences at Cal State LA and now co-author of Between the Tides in California: Exploring Beaches and Tidepools. The book explains why these creatures live where they do, and offers tips on how you can spot them. 

Plate tectonics and earthquakes have influenced the formation of California’s coastline and the diverse ecosystems along it. “These plates sliding past each other have moved whole islands along the coast really slowly, but also shaped our coastline in ways that are really different from what you would find, say along the East Coast or the Gulf Coast,” Krug tells KCRW. 

California also features multiple biogeographic zones, which have different water temperatures and currents. Much of the area is home to what Krug describes as a super productive ecosystem, where winds move nutrient-rich water from the bottom of the ocean to the surface. 

“That's like fertilizer. It fuels the kelp forests and the plankton that live in the water itself, and that sustains all of the life that we find along the beaches. And it just makes for a hugely diverse and really thriving and productive ecosystem.” 

An oystercatcher searches for food on the low tide near Estero Bluffs State Park. Credit: University of Washington Press.

In Between the Tides, Krug splits California into six regions based partly on oceanography, climatology, and geology. “Sometimes it's very local. It might be the proximity to a river. It might be something historical: ‘Why is there black sand here versus white sand there?’ And then sometimes it's regional, so it could be where the major currents are hitting. It could be the local water temperature. It could be something in the circulation, an eddy that recirculates the water off the coast.” 

Point Conception, just north of Santa Barbara, is the distinguishable marine border between the Northern and Southern California regions. When you cross that border, Krug says closely-related species will take each other’s places. 

No ecosystem stays the same forever, Krug points out, and species die off. But some do return, like the sea star, which was almost wiped out over a decade ago due to sea star wasting syndrome. 

In other cases, species live stable lives, like the Hopkins rose, a sea slug. “I went back to the tide pool where I used to collect them 32 years ago in San Diego, and they were still there. And so it was amazing that despite all of the dynamic nature of the ocean, and how much things can change, there are also ways where when you know where something lives, and you know where they hang out, you could reliably find them 30 years later in the exact same spot.”

Like butterflies and poison dart frogs, the bright Hopkins rose uses color to keep away predators like fish and octopus. The invertebrae uses a chemical defense, and as Krug can attest to, tastes “gnarly.” 

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Diverse seaweeds cover the intertidal of Andrew Molera State Park. Credit: University of Washington Press.

Abalone Cove in Rancho Palos Verdes is home to the black sea hare, the world’s largest slug species. When the slugs emerge from their eggs, they are microscopic. But within six months, Krug says the velvety creatures grow to the size of basketballs.

“I've never been to Abalone Cove and not found these giant black sea slugs. … They're always in the same pool. … They're absolutely enormous. And there's usually four of them, and they're usually having a good time, if you catch my drift,” Krug says. “They're just so huge and happy, and they're just sitting there, grazing on brown algae. And if you bother them too much, they'll ink on you.”

Two sea otters float together in Morro Bay. Credit: University of Washington Press.

While writing Between the Tides, Krug also encountered the two-spot octopus at Laguna Beach. The large creature emerged from a deep pool filled with a school of fish. “The fish started swimming around it in this crazy, frenzied circle. And it was like watching a flash mob. … It was amazing and then it went on for 30 seconds. Then, they all just scattered and it was over and no one else saw it but me.”

He continues, “That's the beauty of it. You never know quite what you're gonna see, but if you just allow it to happen, amazing things will unfold for you if you go out and let California's beaches tell you their story.”

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Golden sandstone bluffs back the intertidal in northern San Diego County. Credit: University of Washington Press.

A kelp crab (Pugettia producta) forages on similarly colored seaweed. Credit: University of Washington Press.

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A thumb-sized crab shows off its impressive claws at the Stornetta Lands near Point Arena. Credit: University of Washington Press.

Female elephant seals haul out near San Simeon. Credit: University of Washington Press.

A bat star (Patiria miniata) is exposed on the low tide near Point Lobos State Park. Credit: University of Washington Press.

A kaleidoscope of colorful organisms call a tidepool at Partington Cove home, including sea anemones, purple urchins, California mussels, and orange sponges. Credit: University of Washington Press.



  • Patrick Krug - marine biologist at California State University, Los Angeles