Chronic effects of the organoarsenicals adamsite and triphenylarsine on the intestinal microbiota of Danio rerio.

Organoarsenicals, including the chemical warfare-related adamsite and triphenylarsine (TPA), are contaminants of emerging concern in aquatic environments. While the chronic effects of these compounds on zebrafish (Danio rerio) survival, growth, and other toxicological endpoints have been characterized, the role of gut microbiota in host responses remains unclear. Here, we investigated the effects of 28-day sublethal exposure to adamsite (0.05, 0.15, 0.20, 0.25 μg/L) and TPA (0.73, 0.17, 1.88, 3.00, 4.80 μg/L) on the intestinal microbiota of zebrafish. Microbiota composition and predicted function were assessed using 16S rDNA sequencing and PICRUSt2. Adamsite caused concentration-dependent microbial diversity loss and substantial shifts in community composition, as well as predicted function, consistent with its high toxicity. In contrast, TPA induced only minor changes, with microbial diversity maintained and functional potential retained, reflecting the comparatively lower toxicity. These findings highlight the gut microbiota as a responsive target of organoarsenical toxicity, supporting microbiome-aware ecotoxicological risk assessment.