IP01 Ecotoxicity of Pharmaceuticals
B113 & B114
8:00 AM - 12:00 PM, Monday

(IP009) Structural and functional responses to a mixture of four tetracyclines in aquatic microcosms.

Wilson, C1, Brain, R1, Sanderson, H1, Johnson, D1, Bestari, K1, Sibley, P1, Solomon, K1, 1 Centre for Toxicology, Department of Environmental Biology, University of Guelph, Guelph, Ontario, Canada

ABSTRACT- Pharmaceuticals are routinely detected at low concentrations in surface waters but their subtle effects on non-target organisms are not well understood. Microcosms were used to assess ecological responses in freshwater ecosystems to a mixture of four tetracyclines commonly used in veterinary and human medicine. Triplicate microcosms were treated with tetracycline, oxytetracycline, doxycycline, and chlortetracycline, each at nominal concentrations 0, 10, 30, 100, and 300 g/L for a period of 35 days, resulting in measured time-weighted average total mixture concentrations of 0, 0.080, 0.218, 0.662, 2.29 M. Responses were assessed in terms of structure and function based on measurements on zooplankton and phytoplankton communities, ecosystem productivity, and water quality parameters. Effects were seen in some microcosm endpoints down to the 0.218 M treatment. The largest responses observed were concentration dependent reductions in total phytoplankton abundance and species richness. Zooplankton showed periodic peaks in abundance but were generally unaffected by the tetracycline mixture. Recovery was observed in phytoplankton abundance in all microcosms after treatment was terminated, and resilience (the time to return to normal operating range during stress) was observed in phytoplankton species richness and zooplankton abundance. Responses also included decreased water clarity, and lower oxygen concentration and water temperature. Functional endpoints showed varying sensitivity. Based on dissolved oxygen concentrations, community respiration (R) increased and primary productivity (P) was maintained with increased treatment concentration, despite the decline in phytoplankton. Little is known of the toxicity of metabolites and breakdown products of these antibiotics and their possible contribution to the observed responses. The effects observed occurred at considerably greater concentrations than are currently measured in the environment, indicating minimal risk to aquatic organisms.

Key words: pharmaceuticals, microcosms, tetracyclines, ecosystem function

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