Bacterial community shifts in response to arsenic and cadmium contamination in aquatic ecosystems: a microcosm study

Industrialization and urbanization have led to increased levels of heavy metal pollution in aquatic ecosystems. Heavy metals exhibit toxicity even at low concentrations, posing risks to aquatic organisms, human health, and overall ecosystem health. To investigate bacterial community responses to arsenic (As) and cadmium (Cd) contamination, a microcosm experiment was conducted, followed by 16S rRNA gene amplicon sequencing, and indicator species were identified for each metal. Two concentrations (1 mg L^- 1 and 10 mg L^- 1) of As and Cd were applied separately, and their effects were examined. Bacterial communities in water without sediment changed more rapidly than those with sediment. In contrast, the bacterial communities in sediment and in water containing sediment remained relatively stable. Additionally, bacterial communities responded more sensitively to Cd exposure than to As at equivalent concentrations. A total of two (Rhizorhapis and Methylotenera) and six (Polynucleobacter, Aquabacterium, Curvibacter, Ramlibacter, Methylophilus, and Undibacterium) genera were identified as indicator species for As and Cd contamination, respectively, suggesting that shifts in bacterial communities can reflect contamination by specific heavy metals. These findings highlight the potential of microbial community profiling as an effective tool for the early detection and monitoring of heavy metal pollution in aquatic environments.