“My intake is out there somewhere,” Ali Martinez says as we clomp through red mud to the edge of the pond at the Arboretum to check on her experiment.
A week of heavy winter rains in Flagstaff have changed the terrain of the ‘Arb,’ creeks rushing in ravines usually felted with snow.
“It’s completely inaccessible to me now unless I’m in a kayak.”
We look for the thing a little longer, then give up.
“I don’t even see it,” she says, “but I hear it,” and points to the hose that runs from the bank and is sucking up 40 liters per minute into the contraption she and colleagues built this winter.
In her gaiters, Martinez climbs up to the pump platform. Her movements are sure, efficient, a tell of her background as a long-distance runner and former flight nurse. Martinez is a graduate student in Jane Marks’ lab at NAU’s Center for Ecosystem Science and Society, and she is studying where carbon and nitrogen will go in freshwater food chains in a warmer world.
That’s where the contraption comes in.
“The Kraken,” as Martinez has dubbed it, is a temperature-controlled freshwater experiment housed inside a WeatherPort at the Arboretum south of Flagstaff, a 200-acre expanse that used to be a cattle ranch. The greenhouse structure sits on a raised platform a long stone’s throw from the old ranch foreman’s house. A tarp keeps the pump dry, and we shake a half-barrel’s worth of water from it before going in.
The kraken is a mythic sea-monster, something between a crab and giant squid, and it first appears in the Norse and Icelandic sagas, skulking around the shipping channels of the northern seas and making life miserable for sailors. The kraken’s hold on both the Western scientific and literary imagination is long. Carl Linnaeus, the Swedish naturalist credited with inventing modern scientific nomenclature, includes ‘Kraken’ in his 1735 Systema Naturae. It shows up in Jules Verne’s 20,000 Leagues Under the Sea, and in Herman Melville’s Moby Dick. In 1830, Alfred Lord Tennyson publishes a sonnet called “The Kraken,” one I didn’t know before, and which contains these lines: “There hath he lain for ages, and will lie/Battening upon huge seaworms in his sleep,/Until the latter fire shall heat the deep.”
Inside the WeatherPort, 48 cylindrical chambers—miniature self-contained creeks—burble and hum. It’s warm and humid compared to the bone-dry air outside, and the afternoon light through the PVC walls is translucent, tent-like. An orderly tangle of tubes feed and filter pondwater into each, and crouched on its riser, the contraption does seem cephalopodic: sentient and patient, if a little ominous, too, like something out of some future Bladerunner reboot. Martinez is already busy checking pipe fittings, tanks. The name is fitting, I tell her.
“I named it the Kraken because it’s got so many legs, pipes and tubes,” she says, “and also, at one point, I thought it was going to pull me under. I couldn’t get anything else done.”
To study how nutrients will move in the food chain of warming streams, Martinez and a team of ecologists including her advisor Marks, Ecoss researchers Ben Koch and Zasha Welsh, Alex Flecker (Cornell University) and Steve Thomas (University of Nebraska) constructed this system of miniature streams whose temperatures Martinez can manipulate. The mini-streams have been randomized at three different temperatures: ambient, 2.5 degrees C above ambient, and 5 degrees C above ambient.
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Into each chamber Martinez has dropped either a fast-decomposing leaf—cottonwood—or a slow-decomposing one—oak—and caddisflies to mimic stream foodwebs native to Northern Arizona. A fine-mesh bag containing leaf litter offers food that only the microbes can access. She circles the table, rapping on the waterlines with an old toothbrush to loosen sediment the rains have churned up.
These leaves aren’t just any leaves. Martinez grew the trees in sealed chambers over the summer in the NAU greenhouse. Into these chambers, she pumped 13C, carbon heavier than “normal” carbon—the kind in CO2—by one neutron, and fertilized them with a heavy nitrogen (15N). Her trees used these elements to make their leaves and wood as they would with regular carbon and nitrogen. But like tagging whales or writing in sharpie on a dollar bill, the special heavy isotopes will allow her to trace exactly where in the food chain these nutrients end up.
“We know that temperature speeds up decomposition,” Martinez says, using a red pipe-cleaner (an item I’ve only seen used in craft projects) to clean sediment out of the plastic tubes. “So what we think we’ll see is that the microbes will actually get more carbon and nitrogen than the caddisflies. That has ramifications up the food chain, because fish and bigger aquatic bugs that eat the caddisflies won’t get the elements they need.”
If her hypothesis is right, I ask, does that mean the microbes in the warmer streams are flourishing?
“The microbes are already living large,” she says, “and they’ll respire most of the carbon back into the atmosphere as CO2, which is something we don’t need more of.”
After six weeks of letting the leaves decompose, Martinez will begin to test her hypothesis and see who ate what. She will remove the caddisflies, dry them, grind them up and send them the Colorado Plateau Stable Isotope Laboratory at NAU, which will analyze how much of that specially-labeled carbon and nitrogen from the leaves ended up in their tissue. And using a DNA technique called qPCR, she’ll see which microbes were there, and which ones absorbed the leaf nutrients.
Earlier, I’d taken containers of fake permafrost I’d made in my freezer to a sixth-grade classroom at Sinagua Middle School. I’d explained that as permafrost thaws, microbes are releasing more CO2 into the atmosphere, contributing to warmer temperatures that speed the thaw. One of the students asked, “Does that mean the world is going to end?” I wasn’t prepared for this question, and I confess this to Martinez. Writing down temperatures, she laughs. “Yeah, I sometimes feel like that. I say: ‘well, it’s not going to end, but it’s going to change.’”
Beside us, the Kraken keeps mumbling to itself in its warm and warmer voices.
“I just feel really lucky that this is my project because it’s translatable across a lot of aquatic ecosystems,” Martinez says as we head back to campus.
I roll my window down to hear the improbable winter creek running, rehearsing its testimony on some future season.
“Lots of things are going to warm up,” she says, “so we better find out how that’s going to go down.”