Effects of Triclosan on a Detrital-Based, Aquatic Food Web

The effect of triclosan, a commonly used antimicrobial agent, on various components of a freshwater food web was investigated. A mesocosm experiment was conducted over an 8 week long period, with six treatments comprising a gradient of triclosan concentrations (control, 2.3 μg L-1, 11.5 μg L-1, 23.0 μg L-1, 115.0 μg L-1 and 230.0 μg L-1). These values were based on the maximum environmental concentration detected in a 2000 survey of streams in the United States, which was 2.3 μg L-1. It was found that triclosan had a significantly negative impact on algal growth and leaf decomposition rate. No significant relationship was found between exposure to TCS and microbial metabolism. Similarly, no significant relationship was found between TCS exposure and caddisfly (Lepidostoma unicolor) larval growth and development despite the demonstrated reduction of leaf decomposition by microorganisms. As L. unicolor is a detritivore, the breakdown of organic matter by microbes serves as an important food source. It is possible that any negative effects of TCS on L. unicolor, either directly acting on the larvae or indirectly through their food source, were compensated for by the abundance of food provided. The results from this study suggest that TCS has the potential to influence aquatic ecosystem functions, particularly those involving basic trophic levels, at sufficiently high concentrations. However, there may be subtler effects of TCS not detected here, such as changes in microbial population densities and composition, that may have long-term implications.Science, Faculty ofEarth and Ocean Sciences, Department ofUnreviewedUndergraduat