Editorial: The role of gut microbiota in mediating the physiological and pathological effects of pollutant exposure in aquatic animals

gastrointestinal tract and disturb intestinal homeostasis. In zebrafish, polystyrene microplastic exposure induced intestinal inflammation and oxidative stress and was accompanied by marked changes in both gut microbiota and metabolomic profiles [3]. Long-term dietary exposure to microplastics similarly triggered oxidative damage and pro-inflammatory responses in the gut of gilthead seabream, indicating that plastic particles may directly impair intestinal health in marine fish [4]. A recent meta-analysis further suggested that microplastics predominantly affect aquatic animal gut microbiota by reshaping community structure rather than simply changing richness or diversity, highlighting the need to move beyond alpha-diversity indices when interpreting microbiome toxicity [5]. Pesticides and other emerging pollutants may also alter microbiota-linked host functions. A recent review focusing on freshwater animals emphasized that microplastics and pesticides can affect gut microbial communities and may contribute to behavioral and physiological impairments through microbiota-related pathways [6].Heavy metals and antibiotics provide additional mechanistic evidence for microbiota-mediated toxicity. Cadmium exposure has been shown to disrupt the gut microbiota and aggravate neurotoxicity in zebrafish larvae through a V-ATPase-related mechanism, with germ-free zebrafish models supporting a causal role of microbiota in modulating Cd-induced neurotoxicity [7].Environmental antibiotics, even at sub-lethal and environmentally relevant concentrations, may induce dysbiosis and impair physiological homeostasis, development, and reproduction in fish and aquatic invertebrates, suggesting that microbiota disturbance is an overlooked component of ecological risk assessment for antibiotic pollution [8]. Together, these studies indicate that pollutant-induced toxicity cannot be fully understood without considering host-microbiota The studies in this collection illustrate three important advances. First, pollutant-induced gut dysbiosis is evident across multiple aquatic taxa, including amphibians, crustaceans, fish, and mollusk-associated microbial systems. Second, microbiota changes are increasingly being linked with host phenotypes such as development, growth, metabolism, mercury accumulation, and environmental adaptation rather than being treated as isolated community shifts. Third, the field is expanding from conventional pollutants to emerging materials such as MXenes and nanoparticles, reflecting the need to evaluate novel contaminants before their ecological impacts become widespread. Despite these advances, important challenges remain. Many studies still rely primarily on 16S rRNA sequencing and correlation-based interpretation, which limits causal inference. Future research should incorporate germ-free models, antibiotic-mediated microbiota depletion, fecal microbiota transplantation, probiotic supplementation, and microbial metabolite rescue experiments. Multi-omics strategies integrating metagenomics, metatranscriptomics, metabolomics, host transcriptomics, and immune or neuroendocrine endpoints will be essential for identifying functional mechanisms. More attention should also be paid to chronic low-dose exposure, pollutant mixtures, field validation, sex-and population-specific responses, and microbiota-based biomarkers for ecological risk assessment.Overall, this Research Topic demonstrates that gut microbiota research is becoming a key frontier in aquatic toxicology. By moving from descriptive dysbiosis toward mechanistic and causal models, future studies will improve our understanding of how aquatic animals respond to pollutant stress and may provide new strategies for environmental monitoring, aquaculture health management, and pollution mitigation.