One might think that they no longer seem so diluted – but now a study shows that the low concentrations of psychotropic drugs in the environment can also change the behavior of aquatic animals: the influence of antidepressants makes crayfish more risk-taking, which makes them potentially a risk makes easier prey for predators, report biologists.
People not only treat themselves with medication: residues of the substances end up in the wastewater and thus ultimately in the environment as a result of excretions during therapy or improper disposal. As studies have shown, the pollution of water bodies in many regions of the world has risen sharply in the last few decades. Studies have already shown that some substances can have a critical effect on living beings. In the current study, the researchers led by Alexander Reisinger from the University of Florida in Gainesville have now targeted a special group of active ingredients: the antidepressants, which are used in large quantities to treat mood disorders.
Crayfish in sight
“Traces of these substances are found in many bodies of water,” says Reisinger. “We now wanted to find out to what extent these quantities can affect typical inhabitants of inland waterways: We have investigated how crayfish react when they are exposed to antidepressants in the quantities that can be found in streams and ponds today,” says Reisinger. The researchers carried out their investigations on the crayfish species Faxonius limosus, which is widespread in North America and Europe. These omnivores play an important role in aquatic ecosystems, explain the biologists.
For their study, they built artificial streams in the laboratory that were largely similar to the natural habitat of the crabs. Some of the test animals were exposed to realistic amounts of the antidepressant citalopram for two weeks. It is a widely used drug from the group of selective serotonin reuptake inhibitors that increases the amount of an important neurotransmitter in the nervous system. In the experiments, crabs that lived in artificial streams with clean water served as controls. To test whether exposure to the antidepressant changed the animals’ behavior, the researchers used a so-called Y-maze. This system has a short entrance area that branches into two corridors, like the letter Y.
At the beginning of the experiment, the scientists placed each crayfish in a container that served as a shelter and was located at the entrance to the maze. After opening this shelter, the researchers recorded how long it took for the crabs to venture out. At the fork in the Y-maze, they then had the choice between a corridor from which the smell of food emanated, while the other emitted odorous substances that signaled the presence of another crayfish. The researchers recorded which direction the crabs chose and how long they stayed outside the shelter.
Potentially easier prey
The evaluations showed: Compared to the control group, the cancers that were given antidepressants came out of the shelter earlier – so they were more courageous. They were then comparatively little interested in the path to conspecifics – they preferred to search for food. These changes in behavior could have critical consequences, emphasize the scientists: The increased risk appetite due to the effects of the drug could make the crabs easier prey for predators, thereby changing their populations. In addition, increased foraging could lead to higher rates of decomposition of organic matter, thereby changing the nutrient flows in water bodies. “Both effects could in turn have cascading effects,” says Reisinger.
Says senior writer Emma Rosi of the Cary Institute of Ecosystem Studies in Millbrook, “Pharmaceutical toxicity assessments often focus on lethal effects, but it is mostly unclear how drugs can affect non-target organisms without killing them by changing behavior which in turn can have ecological consequences. More work is needed to understand how pharmaceutical pollution affects life in aquatic environments at a chronic, sub-lethal level, ”says Rosi.
Improved wastewater treatment processes could help contain the problem – but everyone can also make a contribution, the researchers conclude: “Of course, people must continue to take their medication. But one way you can prevent drug residues from getting into our waters is through proper disposal, ”says Reisinger. Above all, the following applies: Do not pour residual medication down the drain.
Source: University of Florida, Cary Institute of Ecosystem Studies, article: Ecosphere, doi: 10.1002 / ecs2.3527