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.

Chronic toxicity of sediment-bound triclosan on freshwater walking catfish Clarias magur: Organ level accumulation and selected enzyme biomarker responses.

Triclosan (TCS) is a biocide widely used in personal care and medicinal products. TCS persists in sediments and has been detected worldwide, making sediments a vital route of TCS exposure to aquatic organisms. This experiment explored the bioaccumulation and toxicological effects of TCS-contaminated sediment. The study revealed that the half-life of TCS in the sediment-water system was 21.52 days. Exposure of Clarias magur juveniles to 0.4 and 0.8 mg kg-1 TCS-spiked sediment resulted in high Biota-Sediment Accumulation Factor (BSAF) with the highest bioaccumulation in the liver (29.62-73.61 mg kg-1), followed by gill (9.22-17.57 mg kg-1), kidney (5.04-9.76 mg kg-1), muscle (2.63-4.87 mg kg-1) and brain (1.53-3.20 mg kg-1). Furthermore, a concentration-dependent increase in oxidative stress biomarkers such as superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST) was documented during 45 days of exposure in gill, liver, kidney, muscle, and brain tissues of exposed fish. A similar increasing trend was also recorded for liver transaminase enzymes such as glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) during the experimental period compared to control. Serum biochemical analysis revealed a significant time and concentration-dependent increase in serum glucose, serum GOT, and serum GPT, while serum total protein and albumin decreased significantly during exposure. These findings demonstrate high bioaccumulative and toxic nature of TCS in fish, promoting multiple physiological and biochemical dysfunctions through sediment exposure. The study underscores the urgent need for strengthened regulations and robust monitoring of triclosan across various environmental matrices, including sediment, to mitigate the detrimental impacts of TCS effectively.