Toxicity of ciprofloxacin and ofloxacin to Moina macrocopa and investigation of p-value adjustments for (eco)toxicological studies

Multigenerational testing reveals delayed chronic toxicity of bisphenol A to Daphnia magna: A common characteristic of endocrine-disrupting chemicals?

Bisphenol A (BPA) poses longstanding environmental concerns due to its widespread presence and recognized toxicity; however, its multigenerational ecotoxicity, in aquatic models such as water fleas, remains incompletely understood. This study examined the impact of sublethal BPA exposure on Daphnia magna across six generations, tracking changes in both life-history and population traits. Over the first five generations, BPA exposure produced minor and inconsistent effects on age at first oogenesis, age at first offspring production, growth rate, and fertility. The sixth generation exhibited prolonged oogenesis, delayed first offspring production, reduced body size, and decreased fertility, indicating delayed adverse effects. These multigenerational effects did not significantly alter population size or dynamics. Furthermore, BPA exposure did not affect feeding behavior in D. magna over six days, suggesting that food consumption-mediated mechanisms were unlikely a contributing factor. Our findings reveal BPA's delayed adverse effects on D. magna fitness, underscoring potential vulnerabilities for D. magna and other species under additional environmental stressors. These results support literature indicating that endocrine-disrupting chemicals can cause delayed and cumulative adverse effects on zooplankton descendants. Broadening multigenerational research to include a wider range of species, alongside sub-organismal analyses, is crucial to advancing regulatory frameworks and understanding underlying mechanisms.

Multigenerational ecotoxicity of tris(2-butoxyethyl) phosphate to the tropical water flea Ceriodaphnia cornuta and probabilistic ecological risk assessment in freshwater environments

The widespread use of the organophosphorus flame retardant tris(2-butoxyethyl) phosphate (TBOEP) and its presence in aquatic environments pose a hazard to wildlife. This study investigates the chronic ecotoxicity of TBOEP at environmentally relevant concentrations (6 ± 0.7 µg L-1) in the tropical water flea Ceriodaphnia cornuta over seven generations. Delayed toxicity emerged from the second generation (F1) to the fourth generation (F3), affecting survival, body length, and fertility. Recovery occurred in F4, followed by complete inhibition in F5 and F6, where no organisms survived beyond day 10. Population dynamics revealed minimal growth in F5, leading to extinction by F6. This is the first study to demonstrate the multigenerational lethal effects of TBOEP at environmentally relevant concentrations, highlighting ecological threats to C. cornuta and other sensitive species. The mechanisms underlying these effects remain unclear and require sub-organismal investigation. The chronic predicted no-effect concentration, estimated at 8.64 µg L-1, exceeds the tested concentration and therefore may not adequately protect vulnerable species. Ecological risk assessments based on TBOEP concentrations detected in surface waters since 2014 suggest potential risks at elevated levels in specific locations across multiple countries. Additional research is essential to validate TBOEP's toxicity across species under chronic and multigenerational exposure. Current ecological risk assessments likely underestimate TBOEP's threat to aquatic ecosystems, emphasizing the need for reassessment to better safeguard biodiversity.

Ecotoxicity of the fluoroquinolone antibiotic delafloxacin to the water flea Simocephalus vetulus and its offspring under the influence of calcium modulation

Delafloxacin (DFX), one of the latest additions to the fluoroquinolone antibiotics, is gaining heightened recognition in human therapy due to its potential antibacterial efficacy in a wide range of applications. Concerns have arisen regarding its presence in the environment and its potential interactions with multivalent metals, such as calcium (Ca). The present study investigated the trans- and multigenerational effects of environmentally projected concentrations of DFX (100-400 μg DFX L-1) on individual- and population-level responses of parental S. vetulus (F0) and its descendants (F1) under normal (26 mg L-1) and high (78 mg L-1) Ca conditions. Exposure of the F0 generation to DFX under the normal Ca condition resulted in reduced juvenile body length (JBL), increased age-specific survival rate (lx), indicating prolonged developmental time, reduced age-specific fecundity rate (mx), and decreased population growth rate (rm). Under the high Ca condition, JBL, mx, and rm were adversely affected. Transgenerational effects of DFX existed, as F1 individuals exhibited persistent suppressions in at least one endpoint under both Ca conditions even after being transferred to a clear medium. Continuous exposure of the F1 generation to DFX had negative impacts on JBL, mx, and rm under the normal Ca condition, and on JBL and rm under the high Ca condition. However, cumulative effects were not observed, suggesting the potential development of tolerance to DFX in the F1 organisms. These findings suggest that DFX is a harmful compound for the non-target model organism S. vetulus and reveal a potential antagonism between DFX and Ca. Nevertheless, the interaction between other (fluoro)quinolones and Ca remains unclear, necessitating further research to establish this phenomenon more comprehensively, including understanding the interaction mechanism in ecotoxicological contexts.