Field and in vitro evaluation of ammonia toxicity on native fish species of the central region of Argentina

HUED, A. C.; CARUSO, M.; WUNDERLIN, D.; BISTONI, M. A

BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY

Lugar: Florida, USA; Año: 2006 vol. 76 p. 984 - 991

0007-4861

Ammonia occurs naturally in unpolluted water bodies at low concentrations. However, high ammonia levels could be an indication of organic pollution such as from domestic sewage, industrial waste and fertilizer run-off. In aqueous solution ammonia assumes equilibrium between ionized (NH4+) and unionized (NH3) chemical species. Its toxicity has been primarily attributed to the un-ionized form, with the ionized form being relatively nontoxic. The effects of environmental ammonia on fish have been widely studied in the North Hemisphere. On the contrary, the knowledge of short-term responses to ammonia in native fish species of South America is still limited. Argentina, as a developing country, has not yet faced severe pollution problems as highly industrialized countries have suffered. However, the faecal and organic pollution in different water bodies of the country are the main problems and accelerate water quality deterioration. The Suquía River Basin, an important lotic system of the central part of Argentina, located in Córdoba Province, has pristine headwaters. On the contrary, the central and lower sections of the basin are characterized by the presence of densely populated urban settlements and an increasing environmental impact due to anthropogenic activities. Pesce and Wunderlin (2000) identified ammonia and nitrite among the main toxicants associated with sewage pollution in the basin. These degraded conditions produce adverse effects on fish, with a marked influence on its abundance and assemblage structure (Bistoni et al. 1999). Reliable data is needed on the sensitivity of native fish species to ammonia and other toxic substances. The main goal of this work was to determine the toxic impact of ammonia on native fish through laboratory experiments. Field assessments were made in order to validate the bioassay results. This paper reports the median lethal concentration of ammonia (24 hr LC50) to three native fish species: Bryconamericus iheringi, Trichomycterus corduvense and Jenynsia multidentata and compares these results with those obtained from field assessments, which were based on changes in natural populations of the three mentioned species.