Pulse-Exposure Toxicity of Ammonia and Propoxur to the Tropical Copepod Acartia sinjiensis
- Publisher:
- Wiley
- Publication Type:
- Journal Article
- Citation:
- Environ Toxicol Chem, 2022, 41, (1), pp. 208-218
- Issue Date:
- 2022-01-01
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Toxicity risk assessments of short term discharges of contaminated waters to the aquatic environment have shown that receptor organisms can tolerate higher pulse exposure than continuous exposure concentrations of some contaminants However these observations are influenced by the mode of toxicity of the contaminants present and the concentration time profile of the exposure For common metal contaminants the time weighted average concentration TAC of the exposure has been useful for predicting risk of toxicity to multiple species including the tropical euryhaline copepod Acartia sinjiensis To increase our understanding of the application and limitations of the TAC approach the present study examined how varied pulse exposure durations affect the toxicity of fast acting contaminants ammonia and the common pesticide propoxur to this copepod species Copepod larvae were exposed under continuous exposure conditions all life stages from eggs to nauplii to copepodites exposed and as 6 and 18 h pulse exposures applied during the most sensitive life stage only 24 h old nauplii within 78 h tests Larval development ratio and population size were assessed as test endpoints Generally increased exposure duration resulted in increased toxicity Trends observed for ammonia and propoxur were slightly different for larval development and population size Larvae tolerated greater concentrations of contaminants in a 6 h pulse higher 10 effect concentration than in an 18 h pulse or a continuous 78 h exposure whereas toxicity responses converged for the 18 and 78 h exposures Continuous toxicity thresholds were always protective of pulse exposures providing a conservative toxicity threshold for all durations of pulse exposures Although generalizations for predictions of risk based on TACs are frequently effective for common metal contaminants the TAC approach was not effective for ammonia and propoxur Environ Toxicol Chem 2022 41 208 218 2021 SETAC 2021 SETAC
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