Impact of Triclosan on Bacterial Biodiversity and Sediment Enzymes - A Microcosm Study

Triclosan (TCS), a widely used antimicrobial biocide, has raised serious concern among the scientific community in recent years owing to its ubiquitous presence around the globe and toxicity to aquatic organisms. The current study investigated the alterations in bacterial diversity, nutrients, and sediment enzyme activity in TCS-exposed sediment. TCS concentrations of 3 mg/L (T1) and 6 mg/L (T2) were applied in a microcosm setup for 28 days to sediment collected from Versova Creek, Mumbai. Among sediment enzymes, dehydrogenase activity exhibited the greatest degree of variability in 3 mg/L exposed sediment. Nitrite, total nitrogen and urease exhibited higher concentrations in 6 mg/L TCS exposed sediment. The concentration of ammonia was observed to be decreasing in treatments exposed to 6 mg/L TCS. Total heterotrophic bacteria exhibited an increase in count in T1 and a decrease in T2. Metagenomics data showed a higher relative abundance of bacteria in T1 compared to T2 on the 28th day of sampling. Proteobacteria was found to be the most abundant phylum in all samples, and their relative abundance was reduced by 0.14% in T₁ and 5.48% in T₂. The results confirm the alterations in the composition of sediment bacterial communities and their enzymatic activities due to TCS exposure.