The researchers also collected eggs, or roe strings, from a separate population of perch and exposed them during the first nine days of embryonic development to three different concentrations of Oxazepam. After hatching, a random group of the fry were collected and analysed.
Results showed that mortality rates were high among hatched fry corresponding to mortality rates found among perch fry in natural populations and relatively high among the two-year-old perch, but were significantly reduced by Oxazepam exposure in comparison to the control group of fish who were not exposed.
In the hatched fry, mortality was lower in the high concentration treatment than in the control and low concentration treatments. In the two-year-old perch, mortality was lower in both the low and high concentrations compared to the control.
Co-author of the study Tomas Brodin, who was the ecologist in the research team, said: "A therapeutic effect leading to increased survival of one species may generate a proportional increase in mortality of that species' prey, which may have cascading ecological consequences that need consideration.
"A new, conceptual view of ecotoxicological testing should include the possibility that a substance can improve the health of an organism and make individuals affected by contamination more competitive than non-affected individuals."
"Even though our study focused on one single pharmaceutical contaminant, it is possible that similar effects could be induced by exposure to a whole range of pharmaceuticals that find their way into surface waters, such as antibiotics, painkillers, anti-inflammatory drugs, hormones and antidepressants. Our conceptual view of a pollutant has, up until now, blocked us from testing for similar effects at environmentally relevant concentrations."
|Contact: Michael Bishop|
Institute of Physics