Toxicity of triphenyl phosphate toward the marine rotifer Brachionus plicatilis: Changes in key life-history traits, rotifer-algae population dynamics and the metabolomic response

Abstract

Triphenyl phosphate (TPhP) is used as a flame retardant that gradually leaks from products into the marine environment and thus may threaten low-trophic-level marine organisms, such as zooplankton. To assess the effect of TPhP on these taxa, we treated the marine rotifer Brachionus plicatilis as a target and examined the changes in key life history parameters and the metabolome after exposure to TPhP at 0.02, 1 and 5 mg/L. Additionally, the rotifer-Phaeocystis population dynamics (a simulation of the prey-predator relationship) were studied under TPhP stress. Our results showed that TPhP at 1 and 5 mg/L reduced the average lifespan and the total offspring number and prolonged the prereproductive time, suggesting damage to survival and fecundity. In the 0.02 mg/L group, no obvious damage occurred in the overall condition of rotifers, but the volume of parental rotifers after the first brood decreased. This implied that rotifers sacrificed somatic growth to reproduction in the initial period of TPhP exposure at the low concentration. All the tested TPhP concentrations altered the rotifer-Phaeocystis population dynamic changes, especially that 1 mg/L TPhP reduced the ability of rotifers to remove this harmful alga, as evidenced by the decrease in the maximum population density of rotifers and the extended time to P. globosa extinction. At the molecular level, metabolomics identified 84 and 206 differentially expressed metabolites, most of which were enriched in glycerophospholipid metabolism, steroid biosynthesis and sphingolipid metabolism. Nile red staining showed a decrease in neutral lipids in rotifers, further indicating a disorder of lipid metabolism induced by TPhP. Moreover, the balance between ROS production and the defense system was disrupted by TPhP, which contributed to its toxicity. This finding will promote the understanding of the ecological risk and mode of action of TPhP in aquatic environments.