First insights into the bioaccumulation, biotransformation and trophic transfer of typical tetrabromobisphenol A (TBBPA) analogues along a simulated aquatic food chain.

Tetrabromobisphenol A (TBBPA) analogues have been investigated for their prevalent occurrence in environments and potential hazardous effects to humans and wildlife; however, there is still limited knowledge regarding their toxicokinetics and trophic transfer in aquatic food chains. Using a developed toxicokinetic model framework, we quantified the bioaccumulation, biotransformation and trophic transfer of tetrabromobisphenol S (TBBPS) and tetrabromobisphenol A di(allyl ether) (TBBPA-DAE) during trophic transfer from brine shrimp (Artemia salina) to zebrafish (Danio rerio). The results showed that the two TBBPA analogues could be readily accumulated by brine shrimp, and the estimated bioconcentration factor (BCF) value of TBBPS (5.68 L kg-1 ww) was higher than that of TBBPA-DAE (1.04 L kg-1 ww). The assimilation efficiency (AE) of TBBPA-DAE in zebrafish fed brine shrimp was calculated to be 16.3%, resulting in a low whole-body biomagnification factor (BMF) in fish (0.684 g g-1 ww). Based on the transformation products screened using ultra-high-performance liquid chromatograph-high resolution mass spectrometry (UPLC-HRMS), oxidative debromination and hydrolysis were identified as the major transformation pathways of TBBPS, while the biotransformation of TBBPA-DAE mainly took place through ether bond breaking and phase-II metabolism. Lower accumulation of TBBPA as a metabolite than its parent chemical was observed in both brine shrimp and zebrafish, with metabolite parent concentration factors (MPCFs) < 1. The investigated BCFs for shrimp of the two TBBPA analogues were only 3.77 × 10-10 - 5.59 × 10-3 times of the theoretical Kshrimp-water based on the polyparameter linear free energy relationships (pp-LFERs) model, and the BMF of TBBPA-DAE for fish was 0.299 times of the predicted Kshrimp-fish. Overall, these results indicated the potential of the trophic transfer in bioaccumulation of specific TBBPA analogues in higher trophic-level aquatic organisms and pointed out biotransformation as an important mechanism in regulating their bioaccumulation processes. ENVIRONMENTAL IMPLICATION: The internal concentration of a pollutant in the body determines its toxicity to organisms, while bioaccumulation and trophic transfer play important roles in elucidating its risks to ecosystems. Tetrabromobisphenol A (TBBPA) analogues have been extensively investigated for their adverse effects on humans and wildlife; however, there is still limited knowledge regarding their toxicokinetics and trophic transfer in aquatic food chains. This study investigated the bioaccumulation, biotransformation and trophic transfer of TBBPS and TBBPA-DAE in a simulated di-trophic food chain. This state-of-art study will provide a reference for further research on this kind of emerging pollutant in aquatic environments.

Strong bacterial stochasticity and fast fungal turnover in Taihu Lake sediments, China.

Understanding the assembly and turnover of microbial communities is crucial for gaining insights into the diversity and functioning of lake ecosystems, a fundamental and central issue in microbial ecology. The ecosystem of Taihu Lake has been significantly jeopardized due to urbanization and industrialization. In this study, we examined the diversity, assembly, and turnover of bacterial and fungal communities in Taihu Lake sediment. The results revealed strong bacterial stochasticity and fast fungal turnover in the sediment. Significant heterogeneity was observed among all sediment samples in terms of environmental factors, especially ORP, TOC, and TN, as well as microbial community composition and alpha diversity. For instance, the fungal richness index exhibited an approximate 3-fold variation. Among the environmental factors, TOC, TN, and pH had a more pronounced influence on the bacterial community composition compared to the fungal community composition. Interestingly, species replacement played a dominant role in microbial beta diversity, with fungi exhibiting a stronger pattern. In contrast, stochastic processes governed the community assembly of both bacteria and fungi, but were more pronounced for bacteria (R2 = 0.7 vs. 0.5). These findings deepen the understanding of microbial assembly and turnover in sediments under environmental stress and provide essential insights for maintaining the multifunctionality of lake ecosystems.