Last week, we heard about the tale of the Cuyahoga River -- a river in Ohio that caught on fire multiple times because it was so polluted. The river is now doing much better, but beyond the fact that it’s not on currently fire -- how do we actually know it’s healthier today? That’s when being a water detective really comes in handy. You can find out how to become a water detective at

Plus: Our Moment of Um answers the question: "Why do dogs wag their tails?"

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CHILD: You're listening to "Brains On," where we're serious about being curious.

GIRL: "Brains On" is supported in part by a grant from the National Science Foundation.

MOLLY BLOOM: The Brains On Water Detective Project is supported by funding from the HB Fuller Company Foundation, a proud supporter of STEM education initiatives, and by 3M, improving lives through support of education, community, and the environment.


DETECTIVE: There I was, a flat-footed cop so green, my cheeks still had the imprint of a pacifier. I thought I knew it all and walked my beat like I owned the city. One Sunday afternoon as I patrolled the Cuyahoga River, everything changed. The river was a burning wreck and needed my help. That's when I was approached by an elite unit of crime-solvers, they called themselves H2O, the water detectives.

We helped tamp down that river fire, and I began to work on a whole new world of mysteries. All of them had one thing in common, water; solid, gas, or liquid. Now I'm always on the lookout to protect and serve this wonderfully weird substance. My first line of defense is to use my senses. Water might be in trouble if it's missing things like fish and birds. Follow your nose too. If it smells off, you might need to open up an investigation. I'll be back a little later. Right now, I'm late for a date, with a river.


MOLLY BLOOM: You're listening to "Brains On" from American Public Media. I'm Molly Bloom. And my mind is still reeling from our last episode about how the Cuyahoga River in Cleveland caught fire like a dozen times between the late 1800s and mid-1900s.

ANNIE BAXTER: Yeah, that episode was on fire.

MOLLY BLOOM: Reporter Annie Baxter is back again. Hi, Annie.


MOLLY BLOOM: So I know that after the last fire on the Cuyahoga in the 1960s, the government put a lot of rules in place to regulate what factories and cities could release into the river, not just for the Cuyahoga but for bodies of water all over the country.

ANNIE BAXTER: That's right. Factories and cities had to do a much better job of cleaning up their liquid waste before it could go into waterways. And if they accidentally spilled oil or something into a river, they'd have to report it so it could get cleaned up right away.

MOLLY BLOOM: Last week, we heard that the river is doing better than it was back then. But beyond the fact that it's not currently on fire, how do we actually know that it's healthier today?

ANNIE BAXTER: We look for clues.

HEATHER BERENSON: Turn your attention to the Cuyahoga River, keep your feet still, close your eyes, and just listen.

ANNIE BAXTER: That's a park Ranger named Heather Berenson. And we're going to tag along with her on a trip to the Cuyahoga River National Park near Akron, Ohio. That's where she and a bunch of middle schoolers will test the water with test kits from an organization called EarthEcho.

MOLLY BLOOM: And, by the way, we have a number of those test kits available at a discount to "Brains On" listeners at

ANNIE BAXTER: Right. So this park ranger Heather, she asks the kids to use their senses before doing chemical tests to gauge the water's health. One boy, Owen Wright, closes his eyes.

OWEN: It's so relaxing and then just seems clean because of how relaxing it sounds.

ANNIE BAXTER: Next, they sniff the air. Not bad. No nasty smell of dead fish or anything like that. But one girl, Reese Freeman, says she nevertheless gets the sense that this river is polluted.

REESE: And it looks green.

ANNIE BAXTER: They decide to give the river a letter grade of about a C. Not awful, but not water you'd want to drink or anything. Next, they'll see if their hypothesis that it's a sea level river is correct. Roman Aloisi, who's 11, collects a sample of the river using a very sophisticated scientific device.

ROMAN: It's super simple. It's like a-- it's a milk jug tied to a rope.

ANNIE BAXTER: He tosses it into the river and then reels it back.

HEATHER BERENSON: Beautiful. What does that water look like?

ROMAN: It looks good. There's no silt in there.

HEATHER BERENSON: OK, great. All right, clean sample.

ANNIE BAXTER: So not a lot of sand or clay. But now comes the hard part, screwing off the lid of the handy dandy water testing kit, with rubber gloves on.

ROMAN: The struggle's real right now.

ANNIE BAXTER: One of the tests requires pouring the river water into a vial and then dissolving a little tablet into it.

REESE: Then shake it.


Back and forth until the tablets dissolve.

MOLLY BLOOM: So what exactly are they testing for?

ANNIE BAXTER: Oh, you know, the usual; dissolved oxygen, pH, turbidity, these are all clues to figuring out the health of the river.


DETECTIVE: Ah, clues, the peanut butter to my jelly, the macaroni to my cheese, the ketchup to my mustard. Say, I think I might need some lunch. Well, before I hit the diner, I've got to follow the leads in this river case I'm working. There's nothing like going straight to the source to see if there's a real problem. First thing I check, turbidity, how cloudy is the water.


The cloudier the water, the more there is to hide. Of course, I've got to look at the pH too. The pH scale tells me how acidic the water might be. A pH of 7 is neutral, which means right in the middle. But once it starts creeping towards 0, more acid enters the scene. Too much acid could send this river to the big sleep.

One last clue I've got to check out, dissolved oxygen. Low amounts of dissolved oxygen and water could mean a watery grave for animals that live here. I'm no hater, but I know that farmers need water and nutrient-rich fertilizer to grow their crops, but fertilizer runoff can be bad news for water.


You get a couple of dark and stormy nights where the rain washes the nutrients into a river and, boy, oh, boy, a whole bunch of bad stuff starts to happen. Algae starts to grow, and the next thing you know, the dissolved oxygen levels in the water go down. Fish need dissolved oxygen to breathe, and without it, the outcome could be curtains. Those nutrients that algae like to gorge on, they can also come from water treated at wastewater plants and even from the fertilizer we use on our own lawns. Next order of business, cookies and milk. Time for lunch. I'll hand this off to you, junior water detectives.

MOLLY BLOOM: So, Annie, what did your junior water detectives find?

ANNIE BAXTER: Let's see. They've got to let the water sit for a couple of minutes before they read the results.

GROUP: 5, 4, 3, 2, 1.

ANNIE BAXTER: Each group gets its result, then they assign letter grades. PH turns out looking the best with a letter grade of B. But the other grades are not so hot. Dissolved oxygen gets a low D, almost enough. The kids have a hard time stomaching these numbers, especially Roman.

ROMAN: What I don't get is an F badder is it good?

HEATHER BERENSON: We're going to talk a little bit about what that means, but an F is never a good thing.

WOMAN: You were hoping it. You were hoping it meant the opposite, huh?


ANNIE BAXTER: But overall, the picture is not horrible. They average all the grades and find the river gets about a C.

MOLLY BLOOM: Right along the lines of what the kids hypothesized in the first place.

ANNIE BAXTER: Totally. Ranger Heather says, even though everyone wished the grade were higher, the thing to remember is that the results can change a lot week to week, or even at different parts of the day. If it rains tonight and you get a ton of phosphorus and nitrogen washing down into the river, the tests could turn out really differently.

HEATHER BERENSON: So where dissolved oxygen can go from an A to an F overnight, the population of animals in this river are not going to be able to do that. They don't have the ability to be like, OK, it's raining, let's move 20 miles down river to the better home.

ANNIE BAXTER: In other words, the true test of the water's quality is the kind of critters that decide to call it home. The water has to be decent enough over long enough a period of time for them to stay there. There aren't hotels for fish, birds, and other critters to go to if the water has a bad day.

MOLLY BLOOM: Annie, before we try to track down the critters of the Cuyahoga, I have another mystery for you. It's time for the mystery sound.


GIRL: (WHISPERING) Mystery sound.

MOLLY BLOOM: Here it is.


OK, Annie, what is your guess?

ANNIE BAXTER: Gosh, that-- I heard some insects in there. I once visited an apiary where they kept bees, and it sounded like some bees to me, maybe.

MOLLY BLOOM: OK, some bees. Excellent guess. We'll be back with the answer in just a little bit.


"Brains On" is working on a brand new show all about the history of things around you, you know, video games, emojis, umbrellas. With that in mind, we need you to record answers to a question about skateboards. How would you design the skateboard of the future? What would it do? What would it look like? Go to to submit your answer. is also the place you can send us all your cool drawings, mystery sounds, high-fives, and questions, like Luke did.

LUKE: Why do dogs wag their tails when they are happy?

MOLLY BLOOM: We'll hear the answer to that question at the end of the show, along with the latest additions to the Brains Honor Roll. Stick around.

You're listening to "Brains On" from American Public Media. I'm Molly Bloom. And with me today is reporter Annie Baxter.


MOLLY BLOOM: Hi, Annie. Annie had taken us to a park near Akron, Ohio, where a whole bunch of kids were using water test kits to see how healthy the Cuyahoga River is.

ANNIE BAXTER: Remember, one way to check on the health is to look for signs of life in and around the water. The kids pull on some rubber boots before wading into the river.

HEATHER BERENSON: The boots are not meant to look good. They are not meant to be good for walking.

ANNIE BAXTER: Ranger Heather is asking them to kick around the rocks at the bottom of the river that will turn up some of the critters living there. They're using nets to scoop up tiny creatures, mostly invertebrates. Those are critters that don't have backbones. They're the kind of stuff fish would eat. Maya White, who's 11, then compares the critter in front of her to pictures on a guide sheet.

MAYA WHITE: Uh, it looks like the midge larva, but it has legs, and none of them look like it.

HEATHER BERENSON: OK, so then we know it can't be a midge larva. So it has legs. Tell me how many legs it has.

MAYA WHITE: It's either four or six.

ANNIE BAXTER: Turns out it's a young caddis fly. It's still in larva form. And finding a caddis fly is a positive sign. Caddisflies are really sensitive to pollution, so if they're there, that's good. Ditto for the other critters they find; crane flies and mayflies. Ranger Heather says all these critters add up to something important. Because those invertebrates find the water clean enough to live in, many other creatures up the food chain have returned to the Cuyahoga. They have food sources.

HEATHER BERENSON: At one time, there was no oxygen in parts of the water, so there were no mayflies, so there were no fish, and there were no bald eagles hunting fish. How many of you have seen a bald eagle in Cuyahoga Valley National Park?

ANNIE BAXTER: Several kids raise their hands. Another ranger in the park, Josh Bates, says it took almost 50 years to get that wildlife back since the last notorious fire on the Cuyahoga in 1969. But looking at the big picture--

JOSH BATES: This ranger's opinion, that's pretty quick and that's something that we can continue to recognize and celebrate, the return of the Cuyahoga.

MOLLY BLOOM: Well, even though the Cuyahoga isn't totally perfect, it sounds like things are looking up, and that is very good news.

ANNIE BAXTER: That's right.

MOLLY BLOOM: You want to hear some more good news?


MOLLY BLOOM: It's time to go back to that mystery sound. Let's hear it again.


All right, any new thoughts after hearing it again?

ANNIE BAXTER: I'm just thinking back to when I was recording this beekeeper and I had a panic attack because his bees were landing on my microphone, and it freaked me out.

MOLLY BLOOM: Did you get stung?

ANNIE BAXTER: No, but having bees, like, amplified in your microphone is really scary. It makes you think they are in your suit.

MOLLY BLOOM: That sounds-- oh, did you get to wear one of those cool beekeeper suits?

ANNIE BAXTER: I did, yeah, yeah, but I still got very scared.

MOLLY BLOOM: It sounds a little terrifying.


MOLLY BLOOM: Here is the answer.

PEARCY: My name is Pearcy Joy.

HARLAN: My name is Harlan.

LIESL: My name is Liesl.

HARLAN: We live in Austin, Texas.

PEARCY: And that was the sound of our honeybees in our apiary.

MOLLY BLOOM: Annie, you got it exactly right.

ANNIE BAXTER: Wow. Well, you know, when you think bees are swarming around you, the sound of it kind of sticks with you.

MOLLY BLOOM: [LAUGHS] So, yes, you have been in an apiary. You're very familiar with that sound. That's awesome. Yeah, those kids actually live and work on an apiary themselves.


HARLAN: Our apiary is where we keep our seven beehives.

LIESL: That's a lot of bees.

HARLAN: I like to help out by using the smoke or to keep the bees calm.

LIESL: I always wear my bee suit so I don't get stung.

PEARCY: The summer is really hot in Austin. The eggs and the larva in the hive will die if they get too hot.

HARLAN: One of my jobs is to make sure the bees have water. They use that water to keep the hive cool.

PEARCY: My favorite part about being a beekeeper is that we get to send honey to our friends.

HARLAN: I like watching the bees up close so I can see what color pollen they're bringing in.

LIESL: Be nice to bees. They're important.

PEARCY: This is the Honey Brown Farm--

ALL: Signing out.


MOLLY BLOOM: OK, Annie, the Cuyahoga River has been slowly getting stronger. Are there things that kids can do to help keep a river, a stream, or lake near their house healthy and happy?

ANNIE BAXTER: Absolutely. There's one last spot I want to take you to in a suburb of Akron, Ohio. There are some kids at Coventry Middle School who've adopted a little area around a stream, helping to bring it back to life. Here's 16-year-old Maddie Harpster describing what it looked like before they started working on it.

MADDIE: We came out and it was barren. There wasn't really much here except for grass. And it was littered with trash. There wasn't much water here.

ANNIE BAXTER: About 50 years earlier, officials in this town decided to force a stream here underground. They figured it wasn't serving any great purpose, so they put in some baseball fields, a parking lot, and a basketball court. It was a win for pickup basketball games. But the loser, the lake down the hill. All that pavement replaced grasses, flowers, and trees, which had helped soak up pollutants before they reached the lake. Maddie's science teacher, Jim Trogdon, says the pollutants came from a lot of places.

JIM: Yeah, anything, changing your oil in your car and emptying your ashtray out in that parking lot, and then we have that big rain event, and where does it end up?

ANNIE BAXTER: But then in 2015, the town decided to bulldoze some of the pavement and restore the stream and area around it to a more natural state. Jim and his students used EarthEcho water kits to start testing both the stream and the lake it feeds into, and then they went a step further. They planted tons of stuff, including about 1,000 trees. We walk through a big field filled with plants and critters. A minty fresh smell fills the air.

WOMAN: Tell me what we're looking at right now.

MADDIE: Now there is a lot of tall grass, and there's so many different species of plants. There's daisies, other flowers. There's multiple types of trees we've planted. And there's stuff in the water. There's animals living out here. And you could just hear the buzz of the different bugs that have now come to make this their home.

ANNIE BAXTER: All the vegetation does a lot of important work. The roots of the trees and plants help to slow the flow of water heading into the lake down hill, preventing flooding. They filter pollutants. And trees are super duper important for helping to fight climate change. They use up carbon dioxide, that's a greenhouse gas that traps heat in the atmosphere and causes the Earth to warm. Jim Trogdon says the quality of the water in the stream itself has just kept improving over time. He and another one of his students, Colby Ragland, tested it recently and got good results, especially for pH.

COLBY RAGLAND: That looks just about perfect. Maybe 7.1 or 2.

JIM: That's the range we want.

ANNIE BAXTER: Doing all this has shaped what Maddie wants to do when she's older. She wants to be a scientist. But she says kids should know they don't have to wait to be grownups to do something big.

MADDIE: You think you plant a tree and it's just one tree, but that one tree can bring seven different trees, like, from its seeds throughout the years and it pulls in carbon and brings out oxygen. So one small thing does make a difference, and I think kids do need to remember that when helping out the environment.


ANNIE BAXTER: To check on the health of rivers, lakes, or streams, use your powers of observation.

MOLLY BLOOM: Simple water tests can give you clues too, like turbidity, pH, and dissolved oxygen levels.

ANNIE BAXTER: Planting trees and other kinds of vegetation not only looks great but can help revitalize the world around you.

MOLLY BLOOM: Yeah, and anybody can do it.

That's it for this episode of "Brains On." If you're interested in looking at the health of water near you, we've partnered with the citizen science group EarthEcho who helped distribute water testing kits.

ANNIE BAXTER: Go to and find out how to get your hands on your very own EarthEcho water testing kit.

MOLLY BLOOM: Brains On is produced by Marc Sanchez, Sanden Totten, and me.

ANNIE BAXTER: Molly Bloom. Production help from Jon Lambert, Lauren Dee, Lauren Humpert, and BD Zhang.

MOLLY BLOOM: Veronica Rodriguez mixed the show. "Brains On" is supported in part by a grant from the National Science Foundation. And the Brains On Water Detective project is supported by funding from the HB Fuller Company Foundation, a proud supporter of STEM education initiatives, and by 3M, improving lives through support of education, community, and the environment.

ANNIE BAXTER: And before we go, let's get back to the Moment of Um.


LUKE: My Name is Luke. And I live in Ladera Ranch, California. And my question is, why do dogs wag their tails when they are happy?


BETSY ABRAMS RICH: My name is Betsy Abrams Rich. I'm a biological anthropologist. Anthropologists study what it means to be human, and biological anthropologists focus on the biological piece of that puzzle, investigating questions like why our bodies work and look the way they do.

Tail wagging is an instinct, that's a type of behavior that an animal does without even thinking about it. Humans have instincts too. Like, if you touched a hot stove, you would pull your hand away right away. The second thing to know about wagging is it's a kind of communication. Humans tend to talk to each other to communicate, but we also have other ways of communicating. I can wave to you and you'll know what I'm saying hi to you. A dog, however, can't talk except for maybe in the movie "Up", but they can communicate in other ways. And tail wagging is one of the ways they use to communicate.

One problem, however, is that scientists have recently discovered that tail wagging doesn't always mean that dogs are happy. In fact, the way a dog wags its tail tells us a little bit more about what it means. Scientists have found that dogs that wag their tail to the right are actually telling us that they're pretty satisfied, maybe happy, whereas dogs that are wagging their tail to the left of their body are actually a little more anxious or nervous. Dogs, however, that are wagging their tail like crazy are pretty much happy.

Humans don't actually notice very often whether or not dogs are wagging their tails to the left or the right, but other dogs do. Veterinarians say that tail wagging is probably best interpreted as a sign that dogs are interested in interacting. You shouldn't automatically look at a dog that's wagging its tail and assume it's friendly. You should look for the other clues it's giving you in its behavior. For example, if the dog's growling, you know what that means. If the dog's showing you its teeth, you know what that means. Don't approach a dog and assume it's happy just because it's wagging its tail.

MOLLY BLOOM: Now that we're all here together at the tail end of the show, it's time to give a shout out to all the kids who sent in questions, mystery sounds, high fives, and drawings. Our walls are full of your amazing mail. Keep sending it in to Or, if you want to send us snail mail, you can find our mailing address at

Without further ado, here are the latest additions to the Brains Honor Roll.


(SINGING) Brains Honor Roll. Bye-bye.

MOLLY BLOOM: We'll be back next week with more answers to your questions.

ANNIE BAXTER: Thanks for listening.


DETECTIVE: Thanks, Brains On. You're the pepperoni to my pizza.

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