Antidepressant pollution alters crayfish behavior, with impacts to stream ecosystems
Increased foraging and reduced aggression have the potential to alter stream functioning
IMAGE: JUST TWO WEEKS OF CITALOPRAM EXPOSURE CAUSED CHANGES IN CRAYFISH BEHAVIOR. view more
CREDIT: STEFAN, INATURALIST
Pharmaceutical pollution is found in streams and rivers globally, but little is known about its effects on animals and ecosystems. A new study, published in the journal Ecosphere, investigated the effects of antidepressant pollution on crayfish. Just two weeks of citalopram exposure caused changes in crayfish behavior, with the potential to disrupt stream ecosystem processes like nutrient cycling, oxygen levels, and algal growth.
Coauthor Emma Rosi, a freshwater ecologist at Cary Institute of Ecosystem Studies, says, "Animals living in streams and rivers are exposed to a chronic mix of pharmaceutical pollution as a result of wastewater contamination. Our study explored how antidepressant levels commonly found in streams impact crayfish, and how these changes reverberate through stream ecosystems."
Crayfish are a keystone species in streams, where they eat invertebrates, break down leaf litter, and cycle nutrients. They are stress-tolerant and can become abundant in urban waterways. These freshwaters are prone to receiving pharmaceutical pollution from sewer overflows, leaky septic tanks, and treated wastewater effluent that contains pharmaceuticals.
Lead author Alexander Reisinger, an Assistant Professor at University of Florida, Gainesville, says, "Previous research via direct injection found that antidepressants alter serotonin and aggression in crustaceans. Our study found that exposure to low doses of citalopram - at levels currently found in urban streams as a result of pollution - is enough to alter crayfish behaviors like foraging, aggression, and shelter use."
Cary Institute's artificial stream facility was used to test effects of citalopram on crayfish and stream ecosystems. Twenty stream habitats were created with low-nutrient groundwater and quartz rocks and red maple leaf packs that had been colonized with microbes, invertebrates, and algae. Streams were randomly selected to receive one of four treatments: no citalopram + no crayfish, citalopram + no crayfish, crayfish + no citalopram, and citalopram + crayfish. Each treatment was applied to five streams. Three male crayfish were added to each of the 'crayfish' streams.
For two weeks, the team dosed the 10 streams receiving citalopram every other day to mimic low, persistent pharmaceutical pollution found in urban streams. Over the course of the experiment, they monitored indicators that would reveal changes in stream ecosystem functioning, such as dissolved oxygen, temperature, light penetration, and algae. At the end of the two weeks, the behavior of exposed and non-exposed crayfish was tested.
To do this, the team tapped into crayfish's keen sense of smell. They used a tank containing a shelter at one end and a divider down the middle. One side of the tank contained water that had passed by sardine gelatin; the other contained water that had passed by another male crayfish. One at a time, they placed the crayfish in the shelter, then recorded the amount of time it took for each to peek out of the shelter and emerge completely. They also recorded the amount of time spent in the sardine and crayfish signal sides of the tank.
Crayfish exposed to citalopram emerged from the shelter sooner, indicating increased 'boldness'. Exposed crayfish were also more interested in food, lingering in the food-scented area over 3x longer than the crayfish-scented area. Crayfish that were not exposed to citalopram took longer to emerge and divided their time equally between the food and crayfish areas, showing no preference.
Reisinger explains, "Citalopram-exposed crayfish are more attracted to food, and less interested in other crayfish. Less time spent hiding and more time foraging could make crayfish more vulnerable to predators, meaning more get eaten. We would expect increased crayfish foraging to lead to higher rates of leaf litter decomposition and biofilm turnover, altering in-steam nutrient flows. Either of these changes could have cascading effects."
In people, 'metabolism' refers to a collection of chemical processes that regulate bodily functions essential to health like breathing, digestion, and temperature regulation. Stream 'metabolism' includes a variety of indicators like oxygen levels, light penetration, and nutrient cycling, which together shape stream health.
The team used their two-week record of stream indicators to assess changes in the metabolism of each stream. They found that crayfish presence versus absence significantly affects stream metabolism. Effects of citalopram alone were not significant, but results suggest that changes in stream functioning would likely occur over time due to citalopram's effects on crayfish behavior.
Reisinger explains, "With just two weeks of citalopram exposure, we saw marked changes in crayfish behavior. Over months to years, we would expect these changes to magnify. Fewer crayfish could reduce populations of the fish that eat them like trout, bass, and catfish. Changes in algal growth or turnover would alter oxygen levels and nutrient dynamics - key aspects of stream functioning that could cause harmful imbalances in the system."
Rosi concludes, "Toxicity assessments of pharmaceuticals often focus on lethal effects, but it is clear that these drugs can affect non-target organisms without killing them and behavioral changes can have ecological consequences. More work is needed to understand how pharmaceutical pollution impacts stream life at chronic, sublethal levels, and what these changes mean for freshwater quality, ecosystem health, and foodwebs - in streams and beyond."
CAPTION
Three months before the experiment, the team placed packets of dried maple leaves and quartz rocks in a local creek and left them to gather communities of algae, bacteria, fungi, and invertebrates. The colonized leaf packs and rocks were then placed in Cary Institute's artificial streams to mimic a natural stream ecosystem.
CREDIT
AJ Reisinger
Investigators
Alexander Reisinger - University of Florida, Soil and Water Sciences Department
Lindsey Reisinger - University of Florida, Fisheries and Aquatic Sciences Program
Erinn Richmond - Monash University, Water Studies Center, School of Chemistry
Emma Rosi - Cary Institute of Ecosystem Studies
Cary Institute of Ecosystem Studies is an independent nonprofit center for environmental research. Since 1983, our scientists have been investigating the complex interactions that govern the natural world and the impacts of climate change on these systems. Our findings lead to more effective management and policy actions and increased environmental literacy. Staff are global experts in the ecology of: cities, disease, forests, and freshwater.
CAPTION
The spinycheek crayfish used in the study were collected from a local stream.
CREDIT
AJ Reisinger
Not acting like themselves: Antidepressants in environment alter crayfish behavior
Crayfish exposed to low levels of antidepressant medication behaved in ways that could make them more vulnerable to predators
WITH MUSIC
VIDEO: CRAYFISH IN LINDSEY REISINGER'S LAB AT THE UNIVERSITY OF FLORIDA. view more
CREDIT: BRIANNE LEHAN/UNIVERSITY OF FLORIDA
Antidepressants can help humans emerge from the darkness of depression. Expose crayfish to antidepressants, and they too become more outgoing -- but that might not be such a positive thing for these freshwater crustaceans, according to a new study led by scientists with the University of Florida.
"Low levels of antidepressants are found in many water bodies," said A.J. Reisinger, lead author of the study and an assistant professor in the UF/IFAS soil and water sciences department. "Because they live in the water, animals like crayfish are regularly exposed to trace amounts of these drugs. We wanted to know how that might be affecting them," he said.
Antidepressants can get into the environment through improper disposal of medications, Reisinger said. In addition, people taking antidepressants excrete trace amounts when they use the bathroom, and those traces can get into the environment through reclaimed water or leaky septic systems.
The researchers found that crayfish exposed to low levels of antidepressant medication behaved more "boldly," emerging from hiding more quickly and spending more time searching for food.
"Crayfish exposed to the antidepressant came out into the open, emerging from their shelter, more quickly than crayfish not exposed to the antidepressant. This change in behavior could put them at greater risk of being eaten by a predator," said Lindsey Reisinger, a co-author of the study and an assistant professor in the UF/IFAS fisheries and aquatic sciences program.
"Crayfish eat algae, dead plants and really anything else at the bottom of streams and ponds. They play an important role in these aquatic environments. If they are getting eaten more often, that can have a ripple effect in those ecosystems," Lindsey Reisinger added.
In their study, conducted while A.J. Reisinger was a postdoctoral researcher at the Cary Institute of Ecosystem Studies, the scientists wanted to understand how crayfish respond to low levels of antidepressants in aquatic environments.
"Our study is the first to look at how crayfish respond when exposed to antidepressants at levels typically found in the streams and ponds where they live," A.J. Reisinger said.
The researchers achieved this by recreating crayfish's natural environment in the lab, where they could control the amount of antidepressant in the water and easily observe crayfish behavior.
Crayfish were placed in artificial streams that simulated their natural environment. Some crayfish were exposed to environmentally realistic levels of antidepressant in the water for a few weeks, while a control group was not exposed. The researchers used a common type of antidepressant called a selective serotonin reuptake inhibitor, or SSRI.
To test how antidepressant exposure changed crayfish behavior, researchers used something called a Y-maze. This maze has a short entrance that branches into two lanes, like the letter Y.
At the start of the experiment, the researchers placed each crayfish in a container that acted as a shelter, and that shelter was placed at the entrance to the maze.
When researchers opened the shelter, they timed how long it took for the crayfish to emerge. If the crayfish emerged, they had the choice of the two lanes in the Y-maze. One lane emitted chemical cues for food, while the other emitted cues that signaled the presence of another crayfish. The researchers recorded which direction the crayfish chose and how long they spent out of the shelter.
Compared to the control group, crayfish exposed to antidepressants emerged from their shelters earlier and spent more time in pursuit of food. They tended to avoid the crayfish side of the maze, a sign that the levels of antidepressants used in study didn't increase their aggression.
"The study also found that crayfish altered levels of algae and organic matter within the artificial streams, with potential effects on energy and nutrient cycling in those ecosystems," A.J. Reisinger said. "It is likely that the altered crayfish behavior would lead to further impacts on stream ecosystem functions over a longer time period as crayfish continue to behave differently due to the SSRIs. This is something we'd like to explore in future studies."
The study, co-authored with Erinn Richmond of Monash University and Emma Rosi of the Cary Institute of Ecosystem Studies, is published in the journal Ecosphere.
Wondering how you can reduce the levels of antidepressants and other pharmaceuticals in water bodies? There are steps people can take, A.J. Reisinger said.
"The answer is not for people to stop using medications prescribed by their doctor. One big way consumers can prevent pharmaceuticals from entering our water bodies is to dispose of medications properly," he said.
A.J. Reisinger has authored an Extension publication and infographic on how to dispose of unwanted medications properly and keep them out of water bodies.
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