Variation of Tolerance to Isothiazolinones Among Daphnia pulex Clones

Abstract

Isothiazolinones are a family of broad‐spectrum biocides widely used in industry and consumer products. Chloro‐ and methyl‐isothiazolinones (CMIT and MIT) are documented as strong irritants, yet they are still used in a wide variety of applications, including cosmetics, cleansers, hygienic products, and various industrial applications. The subsequent substantial release of these molecules from urban sources into freshwater environments, and their potential impacts on aquatic species, have nevertheless received little attention so far, with few studies reporting on the toxicity of either CMIT or MIT to nontarget organisms. The present study addresses this current knowledge gap by evaluating the acute toxicity to Daphnia pulex (Cladocera) of CMIT/MIT (3:1) and MIT, the two formulations most commonly used by manufacturers. In addition, genetic diversity is known to be a major component of variability in phenotypic responses, although it is largely overlooked in typical toxicity tests. Thus the potential range of responses inherent to genetic diversity is rarely considered. Therefore, to account for intraspecific variations in sensitivity, our design involved eight clonal lines of D. pulex stemming from distinct natural populations or commercial strains. Clones exhibited strong variation in their responses, with median lethal concentration (LC50) values ranging from 0.10 to 1.84 mg/L for the mixture CMIT/MIT, and from 0.68 to 2.84 mg/L for MIT alone. These intraspecific ranges of LC50 values challenge the use of single clones of daphnids in standard ecotoxicological tests and the predictions based on their results. The present study brings new evidence that assessing ecological risk of chemicals while ignoring genotype diversity is neither ecologically relevant, nor a representative evaluation of the diversity of potential adverse outcomes. Environ Toxicol Chem 2023;42:805–814. © 2023 SETAC

Effect of the Non-Steroidal Anti-Inflammatory Drug Ibuprofen on the Chydorid <i>Alona guttata</i> (Chydoridae: Aloninae) and the Rotifer <i>Lecane papuana</i> (Monogononta: Lecanidae) Fed on Different Algal Densities

“…For IBP, Heckmann et al [19] reported EC50 for immobilization at 108 mg/L and non-effect concentration (NOEC) at 40 mg/L, values that are superior to those found with the chydorid used in this study. On the contrary, Du et al [20] reported that D. magna exhibited LC10 and LC50 at 11.9 and 23.5 mg/L, which could be explained due to interclonal differences in D. magna, both within and among commercial and laboratory strains [21]. In our case, we started the zooplankton cultures from a single female and propagated their progeny to diminish that effect; nevertheless, it is understandable that some variations might arise after several generations, but studying interclonal variation is beyond the aims of this research.…”