Sensitivity Study Comparing Daphnia obtusa (Kurz 1874) and Daphnia magna (Straus 1820) Exposure to Treated Kraft Mill Effluents, Diethylstilbestrol, and Androstenedione

Abstract

Kraft mill effluents treated by activated sludge show a reduction in acute toxicity. However, their discharges produce hormonal effects in an aquatic ecosystem, due to the sterols metabolites as androstenedione contained in the effluents. Daphnids bioassays are a powerful approach for determining toxicity. However, there are relative sensitivities depending on the species. The main objective of this study is to determine the sensitivity of D. magna and D. obtusa when exposed to kraft mill effluents, diethylstilboestrol (DES), and androstenedione (AED). The sensitivities were tested using acute bioassay exposed to kraft pulp mill. Moreover, the allometric growth rate of both daphnids affected by DES and AED regarding time were also evaluated for a period of nine days. Variation in the ratio between body length and body width – at the abdominal cavity – over time (k index) was evaluated. Results indicated that AED and DES compounds affected the allometric growth rate of daphnids. Specifically D. magna exhibited more sensitivity when it was exposed to kraft pulp mill.