Antidepressants in rivers bring crayfish too far out of their shell
Drugs polluting waterways causes the crustaceans to put themselves in danger as they search for food
ANTIDEPRESSANTS are putting crayfish at increased risk of predation as drugs seeping into ponds and streams cause them to behave more boldly, a study has suggested.
Crustaceans were found to spend more time searching for food, thereby putting themselves at danger, when water is polluted by medication.
Rising prescriptions of medication to help cope with depression and anxiety have resulted in the increased presence of antidepressants in rivers and oceans, studies have shown.
Researchers placed crayfish in a tank to examine their behaviour. Experts found that when the water was contaminated, the fish were more brazen.
“Crayfish exposed to the antidepressant came out into the open, emerging from their shelter, more quickly than crayfish not exposed,” said Dr Lindsey Reisinger, a co-author of the study from the University of Florida.
“This change in behaviour could put them at greater risk of being eaten by a predator.
“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.”
The team wanted to understand how fish respond to trace levels of antidepressants. They recreated the natural environment of crayfish, controlling the amount of antidepressant in the water and observing their behaviour.
Some were exposed to environmentally realistic levels of antidepressant for a few weeks, while a control group was left in clean water.
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 aggression.
‘Crayfish exposed to the antidepressant came out into the open, emerging from shelter, more quickly than those not exposed, putting them at risk of being eaten’
More than half of people with depression benefit from pharmaceuticals, and the most common is a class of drugs called selective serotonin reuptake inhibitors, or SSRIS.
These work by boosting serotonin levels, a chemical which creates feelings of happiness and lifts one’s mood, in the brain. Eight such treatments are approved for use in the UK, including Prozac.
But ponds and rivers are known to be polluted with trace levels of SSRIS which reach the waterways through improper disposal of medication, such as down the sink or toilet.
Another route which enables the drugs to invade the habitat of fish is via the urine of people taking the medication, which reenters the water system despite being filtered and treated. The research is published in the journal Ecosphere.