AILSA CHANG, HOST:
Something unusual was bubbling underneath the surface of northwest Montana's Flathead Lake this summer - submarines. The sub's pilots were helping cash-strapped researchers - helping them explore the depths of Flathead Lake for free and study the lake's ecosystem. Aaron Bolton with Montana Public Radio explains.
AARON BOLTON, BYLINE: It can be hard for research divers to see what's at the bottom of deep bodies of water, like Flathead Lake, unless, of course, they have a submarine.
UNIDENTIFIED PERSON: You're not claustrophobic, are you?
BOLTON: Well, this will be a good test, right?
UNIDENTIFIED PERSON: That's right. Hank, we have a screamer.
BOLTON: This summer, a group of submarine hobbyists - guys who build subs themselves - spent a week on Flathead Lake as volunteers. One of them is Hank Pronk, who lives in nearby British Columbia. On a recent Tuesday morning, we get into his two-man submarine, smaller than a compact car, already bobbing on the lake's crystal-clear surface.
HANK PRONK: That's bang on 40 feet there. You want me to go down? OK. All right. We're going to dive.
BOLTON: Pronk came to northwest Montana to help researchers explore the bottom of Flathead Lake, which is 380 feet at its deepest point.
PRONK: So we're 14 feet from the bottom right now. We're on a slope, I see.
BOLTON: Pronk's sub is capable of going much deeper than the bio station's research divers' limit of 100 feet. One of the station's research scientists is Jim Craft. He says deep-water research is expensive.
JIM CRAFT: Unless you're going to do a lot with them, to put out, you know, $20,000 or so for a rover or - shoot. I don't know how much a submarine costs.
BOLTON: But he does know they don't do enough research that deep to justify the cost. But the sediment and algae samples collected on this expedition might lead to more deep-water research. Video will also help researchers examine invasive mysis shrimp.
CRAFT: So understanding their habits and what they're doing is really nice.
BOLTON: This scientific reconnaissance wouldn't have been financially feasible for the bio station without Pronk. The sub hobbyists are members of Innerspace Science, a collective that connects researchers with private submarine owners.
ALEC SMYTH: I mean, we started it two years ago.
BOLTON: Alec Smyth is the site's founder.
SMYTH: And it seems to be working out.
BOLTON: The group's seven members solicit expedition ideas from researchers through their website. And because they're not commercial operators, no money exchanges hands. They're just in it for the experience.
SMYTH: It's much more rewarding to use your sub that way than to just putter around and (laughter) - and then just come home with a family video or something.
BOLTON: Smyth hopes the resulting research will bring in more expedition requests.
PRONK: Now, I don't know what is all this stuff in the water.
BOLTON: Back on the bottom of Flathead Lake, sub owner Hank Pronk and a fellow Innerspace Science member have found some of those invasive mysis shrimp beginning their daily migration to feed on the surface.
UNIDENTIFIED PERSON: If there's a current, that thing's moving.
PRONK: Yep. So there they are.
UNIDENTIFIED PERSON: They're so tiny.
BOLTON: The mysis population has fueled an explosion of invasive lake trout since the 1980s, significantly reducing numbers of native trout species. The resulting data from the partnership between the hobbyist sub owners and researchers could help lake managers understand what's happening with trout populations and how they might restore the ecosystem.
For NPR News, I'm Aaron Bolton at Flathead Lake in Montana.
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