San Francisco Chronicle - (Sunday)
TIDEPOOLS ARE LENS INTO OCEAN’S LARGER CHANGES.
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 dimesize 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 the 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 onto their southern frontier. Others are disappearing from their historical homes.
For instance, intertidal zones in Monterey Bay are starting to reflect what was once seen only around Morro Bay, and Bodega Bay’s ecosystems are looking more like Monterey’s — with creatures like the small chocolate porcelain crab and sunburst anemone increasing in number or taking up permanent residence.
In March, Sanford published a paper in Nature’s Scientific Reports detailing a northward shift of 67 species, including bottlenose dolphins and olive ridley sea turtles, during the marine heat wave that occurred between 2014 and 2016. It is the most extreme shift of its kind on record, he says. The paper confirmed speculations that changing global temperatures, including short-term spikes, are reshaping the marine environment.
“The intertidal zone is a barometer of change for what’s going on out in our oceans,” Sanford said. “These communities are changing dramatically, not over the scale of centuries but over the scale of the 14 years I’ve been here.”
And what’s going on in the ocean off the California coast is deeply concerning: Gray whales are washing up dead on California shores in concerning numbers this year — 37 as of June 6, according to the National Oceanic and Atmospheric Administration. More than 80 Guadalupe fur seals have also washed up dead or are barely hanging on to life on California beaches in the first five months of this year, five years into already alarming mortality rates for the species. Domoic acid produced by harmful algal blooms has shut down the commercial Dungeness crab fishery numerous times in the past five years, and fisherman have not been allowed to harvest sardines since 2015, after the population of the small schooling fish collapsed.
And while tide pools might seem quaint in comparison, Sanford keeps a close eye on the intertidal zone, which provides a clear lens into how climate change is affecting the ocean, he says.
“Rocky intertidal zones and tide pools have contributed disproportionately to our understanding of ecology,” he says. “They’ve been used for decades as a model system for studying general ecological ideas.”
A swell rolled in and filled Sanford’s rubber boots with seawater. He didn’t find a chocolate porcelain crab, but squeezed between two rocks just above the low-tide line was a small red abalone, another species with an uncertain future.
Earlier that day, inside the Bodega Bay Marine Lab, Sanford showed off tanks of marine migrants that have recently taken up residence just outside the facility. His collection includes chocolate porcelain crabs, pelagic red crabs, scarlet sea cucumbers and sea butterflies — all species once rare but now common to the Sonoma coast.
Determining which specific species will arrive and which will migrate northward is tricky, Sanford says. What’s certain is that the environment is changing permanently.
“It’s not possible to make dramatic predictions, but the striking change we’ve seen is amazing and indicative of rapid changes in the ocean,” Sanford says. “The great thing about tide pools is you can just walk right out and see what’s happening for yourself.”