Ammonia is one of the most widespread pollutants in aquatic ecosystems of industrialized countries. It is found in a freshwater solution as two different chemical species, the unionized form (NH3) and the ionized form (NH4+), this chemical equilibrium is controlled principally by pH and water temperature. Toxicity of ammonia is caused princi-pally by the NH3. In spite of its high toxicity, there is little toxicological data available on the NH3 effects on fresh-water invertebrate species. The aim of this work was to assess the toxic effects of NH3 on the survival and move-ment of two species of benthic freshwater invertebrates: the amphipod Echinogammarus echinosetosus and the pla-narian Polycelis felina. The LC50, LC10, LC0.01, EC50, EC10 and EC0.01 values (mg/L NH3-N) at 24, 48, 72 and 96 hours of exposure were calculated for both species. The LC0.01 and EC0.01 values were considered as short-term safe con-centrations to avoid mortality and inmobility in both spe-cies of invertebrates. These concentrations could be used as preliminary safe levels for episodic exposures to union-ized ammonia. Additionally the comparison of our results with other species of freshwater amphipods and planarians show the relatively high sensibility of P. felina to unionized ammonia. This species may be a good indicator of union-ized ammonia pollution.

Junta de Comunidades de Castilla-La Mancha

Ministerio de Ciencia y Tecnología

Universidad de Alcalá

6 p.

INIA