Results The bacterial population declined in 500 ppm triclosan ( Figure 2 ) .

1. Effect of Triclosan on a Freshwater Ecosystem Figure 5.Triclosan decreased the survival of ciliates and microalgae. Figure 3.Survival rate of Paramecium over one week at different triclosan concentrations. Error bars: S.E. Figure 1. Triclosan (trichloro-bisphenol), an antimicrobial additive found in over 700 household products. Figure 2. Aerobic heterotrophic bacteria decreased after two weeks in 500 ppm triclosan. Figure 4.Survival rate of bacteria is measured by a standard plate count of a 1 g sample of pond sediment. Lyle Rapp Biology Department, Skyline College, San Bruno CA Abstract Triclosan (trichloro-bisphenol) is an antimicrobial additive in over 700 household products. Studies have shown that triclosan discharged with treated sewage persists in waterways resulting in concentrations up to 500 ppt in river. Although less than 500 ppt triclosan has no direct effect on aquatic plants and animals, the effect on microalgae and protozoa has not been determined. The purpose of this study was to determine the effect of sublethal concentrations of triclosan on the productivity of a freshwater ecosystem. Paramecium and Chlorella were grown in triclosan (5 ppm to 0.0013 ppt) in pond water. The minimum lethal concentration for Paramecium is 1.6 ppb; Chlorella is able to grow in 5 ppm triclosan. The effect of triclosan on an ecosystem is being determined. Triclosan (0.5 to 5000 ppb ) was added to 99 ml pond water and sediments in 150-mL beakers. Beakers were incubated at 25°C in natural light. Population changes for smaller organisms are being determined using an inverted microscope. Metabolic activity is being measured with Vernier CO2 and O2 sensors. The standard plate count will be used to count aerobic heterotrophic bacteria in the sediments. The results of this experiment will help determine differential sensitivities to and effect of triclosan on an ecosystem. • Methods • Triclosan • Serial dilutions (5  10-4 – 5  10-10) of stock 1% Triclosan were made. • Spring water and sediment was collected from a natural spring located on Skyline College campus. It contained many small ciliates and microalgae. Paramecium (Carolina Biologicals, 13-1554) was added for easier counting. • Ecosystems: • Three 150-mL beakers were prepared with 20 mL sediment and 75 mL spring water. • Three 150-mL beakers were prepared with 95 mL spring water. One 150-mL beaker was prepared with 20 mL sediment and 76 mL spring water. • 4 mL Paramecium was added to each beaker • 1mL of a triclosan dilution was added to each spring water ecosystem and water + sediment ecosystem. Controls had no triclosan. • Beakers were incubated in a water bath, exposed to indirect natural light, at room temperature (~27°C) for four weeks. • Bacteria Count • Heterotrophic plate counts were performed weekly for four weeks to count bacteria in the sediment. Nutrient Agar plates were incubated at 35°C. • Metabolism (O2 and CO2 Outputs) • O2 and CO2 Outputs were measured for three minutes once a week for four weeks. A 20 mL pond water sample was measured using a Vernier O2 sensor and CO2 sensor. • Results • The bacterial population declined in 500 ppm triclosan (Figure 2) . • Paramecium and smaller ciliates were killed within 1 week in 1 ppm triclosan (Figure 3). • The bacterial population in the sediment decreased in the highest concentration (Figure 4), 500 ppm, but increased in 5 ppt and 50 ppb. • Microalgae died in the presence of triclosan (Figure 5). • Rotifers were killed within the first week in 50 ppb beakers and decreased by 66.66% in 5 ppt. • The O2 and CO2 content of the water remained constant. Discussion & Conclusion The highest concentration of triclosan, 500 ppm, has a significant effect on population of rotifers, ciliates, and bacteria. Microalgae are affected in all concentrations. O2 and CO2 concentrations did not change over four weeks. Perhaps due to lack of metabolic activity. Data indicate a potential ecological danger if environmental triclosan concentrations increase. However, it is unclear whether death of producers and consumers is due to the death of bacteria. Hypothesis The antibacterial agent triclosan will disrupt an aquatic food chain by killing bacteria. Literature Cited 1. Ciba Specialty Chemical. 1998. Irgasan DP 300, Irgacare MP. Toxicological and Ecological Data. Official Registrations. Technical Brochure 2521. Basel, Switzerland. 2. Coogan, M. A, R. E. Edziyie, T. W. La Point, and B. J. Venables. 2007. “Algal bioaccumulation of triclocarbon, triclosan, and methyl-triclosan in a North Texas wastewater treatment plant receiving stream.” Chemosphere 67(10): 1911-1918. 3. Levy, C. W., A. Roujeinikovai, S. Sedelnikova, P. J. Baker, et al. 1999. “Molecular Basis of Triclosan Activity.” Nature 398: 383-384. 4. Levy, S. B. 2001. “Antibacterial household products: cause for concern.” Emerg Infect Dis 7 (3 Suppl):512-515. 5. Naidenko, O., and R. Sutton. “EPA’s Decision to Support Re-registration of Triclosan.” Letter to the U.S. Environmental Protection Agency. 19 Dec. 2008. Environmental Working Group. <www.ewg.org/files/triclosan_EWGcomments_EPA_121908.pdf> (Downloaded 19 May 2009). 6. Suszkiw, J. “New Test To Detect Triclosan in Water.” Agricultural Research Jan. 2009: 13. 7. Tixier, C., H. P. Singer, S. Canonica, and S. R. Muller. 2002. “Phototransformation of triclosan in surface waters: A relevant elimination process for this widely used biocides—Laboratory studies, field measurements, and modeling.” Enviro. Sci Technol 36: 3482-3489. 8. U. S. Dept. of Health and Human Services. 1998. “Toxicological profile for chlorinated dibenzo-p dioxins.” Public Health Service, Agency for Toxic Substances and Disease Registry; U.S. EPA. Estimating exposure to dioxin-like compounds, Vol. II: Properties, sources, occurrence and background exposures. Office of Research and Development. Review draft. Washington DC. • Background • More than 700 over-the-counter products are being made with the antimicrobial agent triclosan (Figure 1). These products include soaps, deodorants, toothpastes, cosmetics, clothing, and children’s toys (4). • Triclosan blocks the active site of the enoyl-acyl carrier protein reductase enzyme, an essential enzyme for fatty acid synthesis in bacteria (3). • Most (96%) of triclosan is disposed via domestic sewage (1), and because the half-life of triclosan is between 2 and 2000 days, the rate of accumulation is faster than the rate of decomposition (7). • Currently triclosan levels are somewhere below 500 ppt in sewage effluent (6). • Triclosan is a possible threat to public health because accumulation in the aquatic food chain could select resistant bacteria (2,4). • As a broad-spectrum bacteriocide, triclosan could kill large and diverse populations of bacteria thereby permanently disrupting food chains. • Spring water and sediment, gathered from a natural spring located on Skyline College campus, was used to examine the effect of triclosan on a freshwater ecosystem. Acknowledgements •Dr. Christine Case, Skyline College Professor of Biology •Patricia Carter, Skyline College Biology Lab Technician •Stephen Fredricks, Skyline College MESA Director