Discriminating the pH toxicity to Poecilia reticulata Peters, 1859 in the Dunas Lake (Camaçari, BA, Brazil)

Abstract

Toxic potential of the pH reduction to fingerlings of Poecilia reticulata, through acute tox­icity bioassays, as well as the influence of increased pH on the tox­icity were assessed. Acid lake samples (Dunas Lake) were collected during 19 months, and assessed with following treatments: water at local pH (±3.0) and samples with modified pH to 3.5, 3.8, 4.0, 4.3, 4.6, 5.0, 5.5, 6.0, and 6.5. Culture water samples with pH reduced to 3.0 were also assessed. Newborn P. reticulata were exposed during 96 h, and dead/immobile organisms were counted at various time intervals during exposure (short intervals in the beginning and long towards the end). Mean results of LT50 and confi­dence intervals from the Dunas Lake and control water with reduced pH were 1.36 (±0.48) h, and 1.03 (±0.50) h, respectively, with no statistical difference. Samples with increased pH showed a significant reduction in tox­icity, with no tox­icity detected at pH 6.0 and higher. Relationship between pH and lethal tox­icity for fingerlings of P. reticulata demonstrated that pH exerted a strong effect on the survival of this species at the Dunas Lake, explaining about 80% of the tox­icity observed.