Mariz_2023_Zebrafish__

Un-ionized ammonia (NH(3)) is a prevalent contaminant found in aquatic ecosystems, frequently associated with complex mixtures of other toxic contaminants. Early embryo-larval stages of zebrafish Danio rerio became an important model for water quality monitoring, and it is necessary to characterize its susceptibility to NH(3) exposure. Fertilized eggs were exposed to NH(3) concentrations ranging from 0.02 to 5.23 mg NH(3) L(-1) until 168 h postfertilization (hpf). The lethal concentration to 50% of exposed zebrafish during 96 h was 2.07 mg NH(3) L(-1), 25% above the median value reported values for early developmental stages of fishes. Sublethal toxicity endpoints indicated the lowest observed effect concentrations for slow blood circulation at 24 hpf, decreased heart ventricular contractions at 72 hpf, incomplete yolk sac absorption at 96 hpf, failure in swim bladder inflation at 96 hpf, developmental retardation at 96 hpf, decreased total length, decreased swimming speed, altered trajectories, and acetylcholinesterase inhibition at 168 hpf of 0.85, 0.06, 0.15, 0.06, 0.15, 0.61, 1.35, 0.35, and 0.85 mg NH(3) L(-1), respectively. Environmentally relevant NH(3) concentrations can affect zebrafish's early development and larval viability, and our results help discriminate NH(3) contribution to the toxicity of complex environmental mixtures when zebrafish is used in water quality monitoring.