RP8 Ecotoxicology of Agrochemicals and Pharmaceuticals
Thursday, 17 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall
(HAN-1117-809367) Field assessment of oxytetracycline exposure to the freshwater macrophytes Egeria densa Planch. and Ceratophyllum demersum L.
Hanson, M1, Knapp, C2, Graham, D2, 1 Department of Environment and Geography, University of Manitoba, Winnipeg, Manitoba, Canada2 Department of Civil, Environmental, and Architectural Engineering, University of Kansas, Lawrence, Kansas, USA
ABSTRACT- Pharmaceuticals, especially antibiotics, are widely distributed environmental contaminants, but there is a paucity of toxicity data to effectively characterize the risk posed to aquatic ecosystems. A microcosm study was conducted to describe the impacts of oxytetracycline on two species of aquatic macrophyte, Egeria densa and Ceratophyllum demersum. Plants were exposed for a period of 6 weeks at nominal concentrations of 0, 5, 20, 50 and 250 
g/L oxytetracycline, plus 20 g/L oxytetracycline amended with additional nitrogen and phosphorus (all n=3), with toxicity assessment at two week intervals. The influence of species density and competition was assessed by planting the macrophytes as individuals, in pairs of the same species and as pairs of two separate species. Both plant species exhibited an overall decline in growth at the highest tested oxytetracycline concentration, and in the nutrient amended microcosms, and some intraspecies interactions were observed (e.g., root development in E. densa). Colouration in the microcosm water column resulting from elevated oxytetracycline levels appears to play the major role in the inhibition of the development of these plants. Based on the toxicity data generated in this study, we estimate that recently monitored concentrations of oxytetracycline in freshwater environments do not pose a direct risk to these two macrophytes.
Key words: pharmaceuticals, microcosm, plant toxicity