W8 PM Ecotoxicology of Agrochemicals and Pharmaceuticals
Wednesday, 16 November 2005: 1:50 PM - 5:30 PM in 337-338

(MAU-1117-725488) Effect of the fluoroquinolone antibiotic ciprofloxacin on stream microbial communities and detritivorous macroinvertebrates.

Maul, J.¹, Schuler, L.¹, Belden, J.¹, Whiles, M.¹, Lydy, M.¹, ¹ Southern Illinois University, Carbondale, IL, 62901

ABSTRACT- Microbial communities play an important role in stream ecosystem processes such as decomposition of senescent leaf litter and as a primary nutritional source for detritivorous macroinvertebrates or acting as symbionts for energy acquisition. Antibiotics may potentially affect stream microbial communities and associated ecosystem processes; especially since recent stream and river monitoring has indicated the presence of some antibiotics downstream of wastewater treatment plants and animal production facilities. In this study, effects of chronic exposure to the fluoroquinolone antibiotic ciprofloxacin (cipro) were examined on microbial community level physiological profiles (CLPP) and growth indices of stream detritivores (Gammarus spp. and Lepidostoma liba). Microcosm experiments were conducted using stream sediments and water, senesced labile leaf material (Acer saccharum), and organisms. Function of microbial communities (based on carbon source utilization) associated with leaf material varied among control, 1, 10, and 100 g/L cipro exposures after 12 d. Although the most dramatic shift in leaf-associated CLPP from controls was observed with exposure to 100 g/L cipro, variation of CLPP relative to controls was minimal at more environmentally relevant concentrations (1 g/L). For detritivorous macroinvertebrates, condition indices (i.e., mass adjusted for structural size) of Gammarus spp. did not differ among controls and experimental groups receiving 0.1 and 1.0 g/L cipro (p > 0.05). Similarly, mass of L. liba after 30 d exposures did not vary among controls, 10, and 100 g/L cipro treatments (p > 0.05). These results suggest that there may be some effect of cipro on leaf-associated microbial communities. However, the degree to which detritivorous macroinvertebrates or associated ecosystem processes may be influenced is not apparent from these experiments. Future work should focus on identifying specific changes in stream microbial communities as a result of cipro exposure.

Key words: ciprofloxacin, detritivores, ecosystem processes, microbial communities