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Consumer-mediated nutrient recycling is influenced by interactions between nutrient enrichment and the antimicrobial agent triclosan
- Taylor, Jason M., Back, Jeffrey A., Brooks, Bryan W., King, Ryan S.
- Freshwater science 2016 v.35 no.3 pp. 856-872
- anti-infective agents, anti-infective properties, aquatic ecosystems, biogeochemical cycles, ecotoxicology, methanol, nitrogen, periphyton, personal care products, phenol, phosphorus, snails, streams, surface water, urbanization
- The fate and transport of triclosan (5-chloro-2-[2,4-dichlorophenoxy]phenol), a widely used antimicrobial agent in personal care products, in aquatic ecosystems is a growing environmental concern. At ecosystem scales, triclosan potentially interacts with co-occurring nutrient stressors to affect overall biogeochemical cycling through consumer-mediated nutrient recycling pathways. We examined N- and P-excretion rates of snails (Physella spp.) in 12 outdoor experimental stream mesocosms dosed with 3 P treatments crossed with 3 triclosan treatments and a methanol carrier control. Snail N- and P-excretion rates increased with decreasing periphyton C ∶ N and C ∶ P ratios across the P-enrichment gradient. N- and P-excretion rates were significantly higher in the high-triclosan than in the methanol control treatments on day 14, but only in high-P-enrichment streams. However, methanol had positive effects on N- and P-excretion rates in low- and high-P-enrichment treatments compared to nonsolvent controls, but no effect at background P concentrations. Multiple inferences can be drawn from our study. First, whereas many investigators have confirmed that using methanol as a carrier below established regulatory levels does not influence laboratory and mesocosm ecotoxicology responses, our results suggest that low-level methanol concentrations can influence measures of ecosystem function. Second, higher use of triclosan and other antimicrobial agents in commercial products coupled with predicted urbanization and surface-water shortages in the future have the potential to increase triclosan concentrations and shift patterns in consumer-mediated nutrient cycling in aquatic systems because of interactive effects of antimicrobial agents and nutrient enrichment.