Tiny quantities of anti-depressants are affecting the fertility of aquatic wildlife such as crustaceans and molluscs, a new study has shown.

Scientists say they are becoming increasingly aware that drugs like Prozac and Sertraline, the most commonly prescribed antidepressants, are having an impact on aquatic life.

The new research has shown that lower than expected concentrations of the drugs in the water will affect the behaviour and biological make-up of these creatures, including their changing colour, growing bigger and reproducing more.

Dr Alex Ford, a marine biologist from Portsmouth University who has led the research which is published in the journal Aquatic Toxicology, said: "There is a staggering list of prescription drugs passed from humans to wastewater treatment plants and into receiving streams, estuaries, or oceans by direct consumption, metabolism, and excretion or by toilet flushing of old prescriptions."