Vernal pools are home to spectacular residents such as fairy shrimp, but these unusual natural wonders are under threat.
This Fleeting Ecosystem Is Magical, and You Have Probably Never Heard of It or Even Noticed It
This is Episode One of a four-part Fascination. You can listen to Episode Two here.
Christopher Intagliata: Earlier this year I kept hearing that one of California’s most unusual natural wonders was sitting right outside San Diego. But when I pulled my car off the road next to a metal fence behind a landfill and recycling center, I started to have some doubts.
Intagliata (tape): Hey, Chuck.
Chuck Black: Yes?
Intagliata (tape): How’s it going?
Black: Good, Chris.
The entrance to the landfill is not the most impressive entrance to a national natural monument, but it protects it a little bit.
Intagliata (tape): So is this the main entrance?
Black: Yeah, this is the only entrance.
Intagliata: This is Scientific American’s Science, Quickly. I’m Christopher Intagliata.
I’ve always been obsessed with visiting the more extreme corners of my home state, California.
Back before Google Maps and Instagram and all that made it easy to see what stuff looked like before you get there, I’d stare at a big paper AAA map of the state, find some place that looked interesting and drive there in my old Honda Accord.
Those trips took me to the floor of a pitch black lava tube near the Oregon border, so dark inside I couldn’t see two inches in front of my face, and all the way up to the crest of the White Mountains, wandering the bristlecone pines.
But here was a place just a little over an hour from where I grew up that I’d never even heard of: the Miramar Mounds National Natural Landmark.
In a state full of superlatives—the lowest basin and the highest peak in the lower 48, the tallest waterfall in North America, the largest trees in the world—this place protects one of the tiniest wonders.
It’s way less iconic, for sure, but it’s much more special to see—and it’s almost on the verge of disappearing.
A wildlife biologist named Chuck Black had offered to show me around. He’s a caretaker of sorts here. So I hop into his truck, and we drive down a muddy road. It’s pretty flooded in places, too.
Intagliata (tape): Oh, wow, we’re driving through water.
Black: Yeah, it’s fairly deep. But it’s—as long as you stay on the gravel part, you’re okay.
Intagliata: It rained a lot here in California this winter—it’s the wettest winter I can remember in a long time. And all that rain’s been a really good thing for what I came to see: vernal pools.
Vernal pools are a type of seasonal wetland—they’re these dried up muddy spots that, when the water hits them, they transform into shallow little ponds exploding with life.
Chuck hops out of the truck and leads me to an overlook for a better view. It’s a rolling, marshy landscape dotted with scrubby bushes and shrubs.
Black: Vernal pools occur on these mesa tops, which were once at the bottom of an ocean. And when this was a level ocean floor, the shells of clams and crustaceans and things settled down over the millennia and formed a cemented layer, which is called a hard-pan layer.
Intagliata: It’s kinda like the bottom of a swimming pool.
Black: And so if you dig down a couple of feet, you’d swear it was cement that somebody had put out at some time, and that’s why the vernal pools exist.
Intagliata: Right now, you can see the pools everywhere. At first glance, they’re not all that much to look at. But if you zoom in a little closer, you’ll see an abundance of life—dozens of little invertebrates and plants, and they’ve all adapted to take advantage of the opportunity these pools provide.
Chuck stoops down next to one, our boots sinking into the mud, and he drags a little green aquarium net through the water.
[CLIP: Sound of crouching next to the pool]
On the first pass, he pulls up one of the most iconic residents of these pools: the fairy shrimp.
Black: So there we go. You see the fairy shrimp, those are really nice, nice large ones.
Intagliata (tape): And they have two tiny little beady eyes.
Black: Yes, two little beady eyes. They, uh… [trails off]
Intagliata: If you ever raised sea monkeys as a kid, these fairy shrimp are related. They’re tiny, delicate little crustaceans.
And if vernal pools had a mascot, it would probably be these fairy shrimp.
In fact, since this natural landmark is on land owned by the Marines—officially, it is Marine Corps Air Station Miramar—the fairy shrimp actually have become somewhat of a mascot here. They actually make these little patches with them on it.
Black: We have a fighting fairy shrimp medallion that people really laugh at. It’s a fairy shrimp holding a machine gun. And every year, soon after the fairy shrimp show up, I take an aquarium full of shrimp into the commanding officer's headquarters.
Intagliata: I’ll add that because Chuck is the resident wildlife biologist on this base, it probably fits within his job description to drop an aquarium full of fairy shrimp at the commanding officer’s desk.
Black: It's always fun to get that reaction when you take an aquarium full of shrimp and people see them for the first time.
Intagliata (tape): I mean, they’re quite delightful to watch swim.
Black: Yeah, yeah.
Intagliata: He takes me farther down the muddy trail to look at a smaller pool.
Black: Let’s see. Here are some deer tracks. Deer came along, got stuck in the mud.
Intagliata: He crouches down and grabs a little sprig of something….
Black: So this is San Diego mesa mint. If you pinch that and smell it…
Intagliata: Oh, wow.
Black: …oh yeah, it smells just like a mint.
So that’s San Diego mesa mint. And this one is San Diego button celery. That’s Eryngium aristulatum….
Intagliata: Both of those plants are endangered species. Several of the fairy shrimp species that live here are endangered, too.
They’re endangered because a lot of their habitat has been paved over or turned into supermarkets and farmland. Statewide, it’s estimated 90 percent of the pools that once existed have been destroyed.
And maybe that’s why I’d never even heard of this place or vernal pools at all. Most of them are gone. But the ones that are left harbor a disproportionate number of California’s native species, compared with surrounding areas.
Marie Simovich: So there’s branchiopods, ostracods, copepods, cladocerans.... And besides the crustaceans, there’s a lot more.
Intagliata: Truly—a lot more.
Simovich: There’s worms, lots of kinds of insects. If you wanna get small, there’s rotifers and other kinds of ... protozoans. There’s bacteria, there’s algae..., vascular plants. It’s minestrone.
In the next episode, we’ll talk with biologist Marie Simovich and other scientists about the suite of different plants and animals—beyond fairy shrimp—that call these pools home and the one thing that unites a lot of them: a gift for living on the edge.
Science Quickly is produced by Jeff DelViscio, Tulika Bose and Kelso Harper. Music by Dominic Smith.
Don’t forget to subscribe to Science, Quickly wherever you get your podcasts. Head over to Scientificamerican.com for in-depth science news.
For Science, Quickly—I’m Christopher Intagliata.