Heavy Winter Rain a Bounty for Bay Area's Vernal Pools

The shimmering blue ponds of water laid out between the San Francisco Bay and Fremont’s Auto Mall Parkway looked as if they’d been permanently etched into the landscape.

Geese stepped along the edge of one pond as ducks glided across the tranquil waters of another.

But U.S. Fish and Wildlife Service biologist Aidona Kakouros knew better.

She’d been there plenty of times in the late spring and summer, long after the pools had evaporated, revealing some of these watery fields as cow pastures.

“In fact if you come here in summer,” Kakouros said, “you will not recognize the landscape — it’s so dry.”

After a winter of heavy rains, the Bay Area’s systems of vernal pools are glorious — putting on an impressive display of these seasonal bodies of water that appear temporarily each year, while hosting their own eco-systems.

The Fremont pools are part of the federally protected Don Edwards San Francisco Bay National Wildlife Refuge. Kakouros said these ephemeral pools have returned for thousands of years — minus recent years when California was gripped by a historic drought.

“For one year,” Kakouros said, “there were no pools at all.”

On a recent day, Kakouros lead a team armed with nets to scour the pools for their native wildlife. The pools are home to some of nature’s most tenuous creatures, including endangered Vernal pool tadpole shrimp, threatened fairy shrimp and federally threatened California tiger salamanders.

Kakouros said the continued winter deluges have most likely given a boost to the struggling species after years of choking drought.

“You become nervous because many of these species, they can not breed during these years,” Kakouros said.

Heavy Winter Rain a Bounty for Bay Area's Vernal Pools

Kakouros and her team waded waist-high into the pools, twisting nets into the water as one would churn butter. With each burst of frenetic spinning, they would inspect the nets for any sign of the tiny creatures. A group of nearby cows munched grass and took in the scene.

The nets emerged with tiny salamanders and tadpoles, which make their homes in the pools during the winter, and lay eggs and retreat into the land when the water dries up. Kakouros said many of the species look exactly as they did during the age of dinosaurs.

“Every single species living here has adapted to live in this extreme conditions,” Kakouros said, emptying a fairy shrimp into a plastic container where she measured it and then poured it back into the pool.

Kakouros said in normal years the fields are dotted with numerous independent pools. But with this year's heavy rainfall, the pools have merged, forming long strands of rippling water.

“It’s a good year,” Kakouros said. “We like this year.”

Kakouros said later in the spring the spectacular pools will give way to their second act as they dry up and are filled in by wildflowers. She said that although the federal lands are restricted to visitors, the U.S. Fish and Wildlife Service schedules occasional public tours.

Kakouros treaded through the water — her hip-high rubber waders generating a wake as she dipped her net into the water and spun it like a propeller.

“It’s a unique place,” she said. "It’s a place you can discover things every single day.”

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