Newswise — In recent years, amphibian populations around the world have been declining. For example, the Iberian newt has become rare in Spain and Portugal. Simultaneously, human populations have increased, and along with them agricultural demand and the use of chemical fertilizers have increased. Runoff from fields brings chemical compounds such as ammonium nitrate into ponds and streams where they can be toxic to amphibians.
A study published in the March 2011 issue of the journal Herpetologica finds that while embryos of the Iberian newt are not directly killed by these toxins, they do suffer a reduction in growth rate when exposed to the toxins. This can compromise the animals’ ability to deal with other stressors including natural stressors, thereby reducing their probability of survival.
Fields are fertilized in the spring as many amphibians are breeding and laying their eggs. Adult amphibians have a permeable skin, and their eggs have a surrounding gelatinous envelope. These features make amphibians highly sensitive to water pollution.
In the current study, researchers raised embryos of wild Iberian newts in laboratory conditions with varying experimental levels of ammonium nitrate in the water. At the lowest level, the maximum concentration of nitrate legally allowed for drinking water in Europe was used. At the highest level, embryos were exposed to the highest nitrogen concentrations that have been detected in amphibian-inhabited ponds in central Spain affected by agricultural runoff.
At the time of hatching, the exposed embryos were 9.6% smaller than those in control groups, a result that was consistent across nitrate exposure levels. Compared to larger hatchlings, smaller hatchlings may be unable to survive in the larval stage, may face increased risks from predators, and may be less effective in their search for food.
Researchers theorize that organisms are being forced to expend more energy fighting toxins, thus reducing their growth and development.
Full text of the article “Realistic Levels of a Fertilizer Impair Iberian Newt Embryonic Development,” Herpetologica, Volume 67, Issue 1, March 2011, is available at http://www.hljournals.org/doi/full/10.1655/HERPETOLOGICA-D-10-0001.1
HerpetologicaHerpetologica is a quarterly journal of The Herpetologists' League, containing original research articles on the biology of amphibians and reptiles. The journal serves herpetologists, biologists, ecologists, conservationists, researchers, and others interested in furthering knowledge of the biology of amphibians and reptiles. To learn more about the society, please visit http://www.herpetologistsleague.org/en/index.php.
RSS