Commonly prescribed drugs linked to shrimp population decline

A small shrimp

Reductions in the overall shrimp population would damage the wider food web, with shrimp fed on by fish and wintering birds

Study finds that antidepressants in waste water flowing into rivers and estuaries can make coastal marine shrimps more susceptible to predators

Increasing levels of antidepressants and other pharmaceutical drugs finding their way into the water system pose a threat to coastal shrimp populations, according to marine biologists.

Research from Portsmouth University
has found that when small marine shrimps called amphipods were exposed to the antidepressant fluxetine and two other frequently prescribed drugs they became more susceptible to predators by swimming towards light rather than hiding away in darker areas.

Antidepressants are often designed to increase levels of, or reduce the destruction of, the neurotransmitter serotonin, which in humans is known to influence moods and behaviour.

However, in shrimps, changing serotonin levels can cause animals to alter their natural behaviour and swim towards light, making themselves more vulnerable to be eaten by fish or birds.

Pharmaceutical drugs

Prescriptions for antidepressants have risen rapidly in recent years, with more than 26 million written by doctors in England and Wales in 2002, but the environmental impact of such drugs on marine life through the outflow from sewage treatment works is largely unknown.

Study author Dr Alex Ford said coastal water contaminated by such drugs could make these shrimp 10-20 times more likely to be eaten. He said any reduction in the overall shrimp population would damage the wider food web, with fewer shrimp available to predatory fish and wintering birds at low-tide.

'In the future the pharmaceutical industry will probably be regulated more strongly if the evidence points to the effect their drugs are having - they will need to start looking at the full life-cycle of the drug and not just stop at the consumer,' he said, adding that consumers should be made more aware of the potential damage of increasing levels of drugs found in sewage by throwing unused pills down the sink.

Although the study looked at levels only found close to sewage treatment outflows, Dr Ford said the 'cocktail effect' of lots of these chemicals together in small quantities could have a similar impact on marine shrimps.

Useful links

Study: Anti-depressents make amphipods see light

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