06/18/2021

What Can Crayfish Tell Us About Drugs In Our Waterways?

9:36 minutes

close up photo of a grayish-blueish and bug-like crayfish sitting on a rock, likely underwater
The study used spinycheek crayfish. Credit: Wikimedia Commons

Wastewater is a grab bag of chemicals. There’s industrial run-off, bits of animal and viral DNA, and then there are compounds that trickle out from our households. The medicines we’re flushing down the toilet or releasing through urine are making their way into countless bodies of water.

Antidepressants are one of the drugs that frequently end up in the environment. A team of scientists wanted to study the effects of these antidepressants on streams wending their way through ecosystems. So they looked to none other than the crayfish. They found that crayfish exposed to these drugs were a bit bolder. Their results were published this week in the journal Ecosphere.

Freshwater ecologist Lindsey Reisinger and freshwater biogeochemist A.J. Reisinger, who are both authors on that study, talk about how these drugs affect crayfish and potential downstream effects on waterways and the ecosystem.


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Segment Guests

Lindsey Reisinger

Lindsey Reisinger is a freshwater ecologist.

A.J. Reisinger

A.J. Reisinger is a freshwater biochemist.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow. There’s an old expression, you are what you eat. But sometimes other creatures become what you eat, especially if what you consume are drugs.

How do we know? Check the wastewater, and you’ll find it contains a grab bag of chemicals. There’s industrial runoff, bits of animal and viral DNA, and then there are compounds that trickle out from our households. The medicines we’re flushing down the toilet or releasing through urine are making their way into countless bodies of water.

Because anti-depressants frequently end up in the environment, a team of scientists wanted to study the effects of these antidepressants on streams, wending their way through ecosystems. So they looked to none other than the crayfish. They found that crayfish exposed to these drugs were a bit bolder. The results were published this week in the journal Ecosphere.

Joining me now to fill in this story are two authors on that study. Lindsey Reisinger is an assistant professor in the Fisheries and Aquatic Sciences program at the University of Florida in Gainesville. AJ Reisinger is an assistant professor in the Soil and Water Sciences Department also at the University of Florida. Welcome to Science Friday.

LINDSEY REISINGER: Thanks.

AJ REISINGER: Thanks for having us.

IRA FLATOW: Now before I ask what does bolder mean in a crayfish, I have to apologize to folks who call them crawfish, right? It depends on where you live. AJ, please tell us what happens when you take an antidepressant. Let’s begin right there. How much of the drug ends up in wastewater or streams?

AJ REISINGER: Yeah, so we’re prescribed a certain dose by our doctor. That dose is to ensure that we get enough of the medication into our bodies to have the proper effect. But human bodies aren’t 100% efficient at metabolizing drugs, and so different bodies can break down the medications that they take in at different rates.

And so any body might use 70%, 90% of whatever medication [? that they ?] [? can– ?] I’m not sure of the exact percentages– and it’ll vary by compound and by individual. But some portion of what you take into your body as medication your body won’t break down. And so, therefore, it will be excreted directly into your wastewater when you go to the bathroom.

IRA FLATOW: And Lindsey, so why is crayfish a good candidate to look at?

LINDSEY REISINGER: Yeah, so there were several reasons why we chose crayfish. So one reason is that they just tend to be really abundant, and they’re large. So they make up a large biomass in freshwater ecosystems, so they can have major impacts.

Another reason is that some species are tolerant of polluted conditions. So we might find them in a lot of streams or lakes that are receiving some wastewater. And then the third reason is that crayfish are actually a major model system to look at behavior. And so we know a lot about chemicals like serotonin and its effects on crayfish and how that can translate into behavior. What we didn’t know is whether trace amounts of chemicals in the water could affect crayfish behavior.

IRA FLATOW: And you looked at one antidepressant in particular called the citalopram, the brand name Celexa. You conducted this in a lab, an experimental stream. Lindsey, what did you find?

LINDSEY REISINGER: So we tested them in an aquarium, where we first were looking at how quickly they came out of a shelter into a novel environment. And the ones that had been exposed to the drug came out almost twice as fast as the ones that were not exposed. We were pumping in water into this aquarium.

Some of the water was from bucket with a food source, so that water smelled like food. And then the other water had another crayfish in it, so it smelled like a crayfish. And we looked at how much time the crayfish spent going after one of these two scented waters. And if the crayfish had been exposed to the drug, they spent almost three times more going after the food water compared to the crayfish water whereas the other crayfish spent an equal amount of time in both sections.

IRA FLATOW: Is that a bad thing for a crayfish to do?

LINDSEY REISINGER: Well, it’s not necessarily a bad thing. Particularly the fact that the crayfish came out of the shelter more quickly and are bolder suggests that they might be more vulnerable to predators. And if they are spending more time going after food, they could have different impacts on the ecosystem.

IRA FLATOW: Hmm, and AJ, you also looked at possible downstream effects, talking, as we are, about the ecosystem. How could the ecosystem be affected by having these antidepressants in the crayfish and the water?

AJ REISINGER: Within the stream, ecosystems themselves, these artificial stream ecosystems, we found that the crayfish increase the amount of algae in the water column and they also increase the amount of organic matter at the bottom of the stream. But we found that it didn’t matter if the crayfish had been exposed to the antidepressant or not. The antidepressant had a major effect on the crayfish behavior that Lindsey talked about earlier, but that change in behavior didn’t seem to change their impact in our artificial stream ecosystem.

However, we think that might be because our study was fairly short. It was only a two-week study. And so the crayfish– it takes a while for that crayfish behavioral response to show up. This is all hypothetical because we didn’t run the experiment for longer, but a bolder crayfish that’s spending more time foraging for food might be moving around where the nutrients are available and might be changing the bacteria, microbes, and bugs that are in the system and so, therefore, reducing the overall cycling rates in the streams themselves.

IRA FLATOW: Lindsey, any idea what might happen to the animals that eat the crayfish that have eaten the chemicals?

LINDSEY REISINGER: Yeah, that’s a really great question. So one interesting thing that our collaborators have looked into in another study is that some of these compounds in the antidepressants can accumulate in animals. So specifically, they were looking at aquatic insects. And so it might be that the concentration of the antidepressant in the crayfish and in these other aquatic organisms is much higher than it would be in the background stream water.

If a predator is eating a bunch of crayfish or a bunch of these aquatic insects that do accumulate the antidepressant, you could get a higher dose. And so we don’t know exactly what that dose would be. But this is something to think about, for sure.

IRA FLATOW: You know, I’m thinking of a study a few years ago– I think it’s probably a famous study by now– about birth control and wastewater and the feminizing of fish, AJ. Are you familiar with that one? This sounds a little bit in the same ballpark.

AJ REISINGER: Yeah, absolutely, that term is called an endocrine-disrupting compound, so it changes the endocrine system of these organisms. And these endocrine-disrupting compounds, they don’t kill the fish, but they change their behavior. They change their reproduction. They change their life history.

In a previous study that I was a co-author on, we actually argue that pharmaceuticals have a similar effect on the ecosystem. We coined the term ecologically disrupting compounds for pharmaceuticals because, typically, these pharmaceuticals are not at high-enough concentrations to kill organisms, to kill animals in the environment. But a large breadth of studies are now showing that they do have sublethal effects, changing things like crayfish behavior, fish feeding rates, or algal photosynthetic rates, that sort of thing. So despite not having a toxic effect, not killing any animals, they are changing the overall interactions among various parts of aquatic ecosystems.

IRA FLATOW: My last question is, so is there anything we can do to limit the amount of drugs that get into the water, AJ?

AJ REISINGER: The first thing that I tell people, when they ask me that question, is, first off, I’m not telling you– I’m not asking people to stop taking their medications. So do not stop taking any medications because you want to protect the water quality. However, there are proper ways to dispose of your medications.

Often, local pharmacies or drugstores will have medication take-back locations, so drop boxes, cabinets, or daily event– one-day events, where they will take any unwanted medications, no questions asked. Local police departments and sheriff’s office often have unwanted medication drop boxes as well.

But first and foremost, I’d say make sure that you don’t ever flush any medications down the drain. If that’s your last option, it’s much better to put your medications in the solid waste in your trash can. Mix it with some type of unedible trash as well, something like coffee grounds, so that you don’t get unintentional ingestion by another animal. And then have it be taken out with the solid trash because that will allow more opportunity for the compounds to break down in the environment.

IRA FLATOW: Great suggestions. I’m sorry. That’s about all the time we have. I want to thank both of you for taking time to be with us today.

LINDSEY REISINGER: Thank you. It was great to be on.

AJ REISINGER: Yeah. Thanks a lot, Ira.

IRA FLATOW: Lindsay Reisinger, assistant professor in the Fisheries and Aquatic Sciences program at the University of Florida in Gainesville, and AJ Reisinger, assistant professor in the Soil and Water Science Department also at the University of Florida.

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