Not only does water pollution contaminate the source of a vital life element, but it appears to have more surprising effects: changing the sexual classification of male fish.
Over the past few years, an increasing number of fish living in Spanish waters are becoming feminized. These fish, which were originally identified as male, seem to have been affected by chemical pollutants in the Basque Country water. According to research done by a group in Cell Biology in Environmental Toxicology, endocrine-disrupting chemicals acting as estrogens are slowly affecting the waters and creating both reproductive and developmental disturbances. Because of the estrogen behavior of the chemicals, male fish in the estuaries of Basque Country are developing female features.
Such changes were first detected in the Urdaibai estuary in 2007 and 2008. Now, researchers at the University of the Basque Country in northern Spain have found feminized fish in seven other area estuaries. In three of the six estuaries studied, male thick-lipped grey mullet appeared to be intersex, meaning that they had a combination of male and female sex characteristics; in this case, the specimens had testicles that contained immature ova. Additionally, most of the male fish had vitellogenin, a protein that is normally only expressed in females.
Pesticides, contraceptive pills and detergents are thought to have caused the sex change. The increase in estrogen was detected not only in the gonads of the specimens analyzed, but also in different molecular markers. Miren P. Cajaraville of the Cell Biology in Environmental Toxicology group suggests that endocrine disruption has spread all over the estuaries. This prevalence suggests a serious problem with pollutants. Cajaraville thinks he knows the most significant source: The highest amount of polluting hormones can be traced to a single water treatment plant.
By collaborating with the Spanish National Scientific Research Council, the chemical analysis team confirmed the positive correlation between the presence of the pollutants and the observed feminization of male fish.
The results of the studies have been published in two papers, one in the journal of Science of the Total Environment and the other in the journal of Marine Environmental Research.