Mequon Nature Preserve's Fairy Shrimp: Will They Survive?

May 11, 2018

Have you ever heard of fairy shrimp? Until recently, I hadn’t. Mequon Nature Preserve, located at the southern edge of Ozaukee County, is home to the teeny, tiny crustacean.

Picture the kind of shrimp some people love to eat, just way smaller – an inch long, tops. Jason Nickels, the preserve's education and research director, explains: “They’re anywhere from a pink, to a brown, to a green – I think it depends on what they’re feeding on."

And fellow pond dwellers feed on them, he says - including everything from ducks and beetles, to dragonfly and damsel fly larva, to crayfish. “This is just a feast for them.”

Fairy shrimp found in Pat's Pond within Mequon Nature Preserve.
Credit Susan Bence

In search of this tiny piece of a delicate food web, we hike to a small parcel within the 450-acre preserve called Pat’s Pond. Nickels says don’t let its unassuming name or diminutive size deceive you.

“This is by far our best woods, we know they never tried to farm...," Nickels explains. Farmers started tilling everything around as far back as the 1870s, but this area remained untouched – maybe because it was so soggy during the critical growing season.

“It’s only a six-acre wood but it has over 140 native species of plants,” he adds.

Bloodroot in bloom.
Credit Susan Bence

We enter a sea of towering trees. Below, sprinklings of mayapples and graceful white bloodroot blossoms pop out of the earth.

Our destination - the pond where fairy shrimp thrive - swallows the lower trunks of yet more trees.

Nickels gives one simple instruction: ‘Don’t fall in.” Then the gentle bear of a man deftly wades in, net in hand, on the watch for an unsuspecting fairy shrimp.

Within seconds, he scoops the dainty creature into his net. “So here’s your little fairy shrimp. They really are pretty."

I was lucky to see one in the flesh on my visit last week. Fairy shrimp season is short – starting late winter at the earliest and stretching into just about this time of year.

Nickels says when the pond’s water temperatures reach 65 degrees, “the fairy shrimp come to the end of their life cycle... and then water daphnia – another crustacean - kind of take their place in the food chain.”

But the shrimp are not really “gone.” Tens of thousands of their eggs lay at the bottom of Pat’s Pond. “When we get a little influx of melting snow or rain, it perks them up, they’re up there breeding, laying eggs,” he says. 

Jason Nickels scooping up fairy shrimp.
Credit Susan Bence

But such a delicate ecosystem can’t be that simple, right?

Nickels says one key reason fairy shrimp thrive here is because this pond has historically been ephemeral – by late summer, it dries up.

But for the last two years that hasn’t happened. “That’s because all of the trees that you see in the water are ash trees," which have fallen victim to the invasive emerald ash borer.

When the trees were alive and well, they soaked up a lot of pond water, "They collectively soaked up and transpired (out of their leaves) thousands of gallons of pond and groundwater every day," Nickels explains.

But now, he says, there's 100-200 dead and dying trees, and this is resulting in changes in the vegetation.

To add to his worries, Nickels says a wetland about a quarter mile from here contains fish. So, if Pat’s Pond becomes a pond year-round - rather than remaining ephemeral – fish could take up residence here.

“Now it’s a ways from there from here, but if they were to get in here that would drastically alter the food web inside this tiny, little pond,” Nickels explains.

The slow-swimming fairy shrimp would be no match to hungry fish. Work is underway to try to prevent the ecosystem standoff. Crews have strategically removed dead ash trees and other species will take their place. And, Nickels hopes this will fill in the canopy quickly enough to preserve this place for all of its creatures.

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