Tuesday, May 21, 2013
While low levels of pharmaceuticals have been found in lots of other fish, no one, until recently, had looked for them in sharks. Now, bull sharks in Florida join the growing list of species known to be impacted by pharmaceuticals in the environment.
To learn if sharks living in Florida rivers were showing similar drug accumulation rates as other fish, researchers sampled blood plasma from animals living in a river receiving up to 44 million gallons of treated wastewater a day and those living in a river minimally impacted by wastewater. Sharks were collected during the summer with a longline fishing method, which uses many baited hooks on a fishing line laid at the bottom of the river. Blood samples were taken from the sharks, which were then released, and samples were analyzed in the lab for synthetic estrogen, antidepressants, a cholesterol reducer, and an impotence treatment.
Low levels of at least one pharmaceutical were found in the plasma of sharks in the sewage-impacted river, while plasma from only one of the sharks from the reference river contained measurable levels of medicine. The researchers point to these finding as evidence that pharmaceuticals can bioaccumulate in sharks, but, thus far, haven't been measured at levels that would hurt sharks. Since this was a small study, broad conclusions about pharmaceuticals in shark populations can't be made, but their findings do generate some interesting questions about the impact of human waste on organisms that life in both fresh and salt water during their life cycles.
Gelsleichter, J. and N.J. Szabo. 2013. Uptake of human pharmaceuticals in bull sharks (Carcharhinus leucas) inhibiting a wastewater-impacted river. Science of the Total Environment. 456-457: 196-201. http://dx.doi.org/10.1016/j.scitotenv.2013.03.078
Written by Corrie Layfield