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(42-13) Impact of chemical fertilisers on survival and growth of four amphibian species. Saiz, Neli1, Ortiz, Manuel1, Marco, Adolfo*,2, Lizana, Miguel1, 1 University of Salamanca, Salamanca, Spain2 Doņana Biological Station, CSIC, Sevilla, Spain ABSTRACT- An excess of chemical fertilisers can negatively affect aquatic ecosystems. Many aquatic species, including amphibian larvae, are sensitive to levels of ammonium nitrate found in body waters from agricultural areas. The aim of this study is to analyse the effect of this chemical on embryonic and larval stages of four amphibian species that inhabit agricultural areas. We exposed sharp-ribbed salamanders (Pleurodeles waltl), western spadefoot toads (Pelobates cultripes), common toads (Bufo bufo) and natterjack toads (Bufo calamita) to several ammonium nitrate levels from 0 to 200 mg NO3/L during 15 to 20 days. We conducted static experiments that began at the embryonic stage and finished at the larval stage. Previous studies have shown that hatchlings are the most sensitive age to nitrate. Our study showed a significant effect of ammonium nitrate on survival of the common toad. Lethality was observed mainly at the highest concentration (200 mg/L), and average mortality was a 34 % higher than in controls. Moreover, all species were sensitive to that concentration and showed a lower larval growth compared to controls. Mean final larval size at the highest concentration (200 mg/L) was lower than in control, varying this decrease from the 5.35 on the natterjack toads to the 14.54 % on the spadefoot toad. The growth rate and time and size to metamorphosis are very important factors that can decisively influence the fitness and survival of amphibian larvae. These results indicate that chemical fertilisers could be contributing to the decline of these amphibians. The most sensitive species was the common toad and it has disappeared from many agricultural areas of Spain during the last decades. Key words: fertilisers, amphibians, development, mortality |
