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Ecological consequences of antibiotic exposure to periphyton in naturally colonizing stream mesocosms
Citation:
QUINLAN, E. L., C. T. NIETCH, AND J. M. LAZORCHAK. Ecological consequences of antibiotic exposure to periphyton in naturally colonizing stream mesocosms. Presented at North American Benthological Society, Salt Lake City, UT, May 25 - 30, 2008.
Impact/Purpose:
Molecular biological approaches allow for the development of the first diagnostic indicators which (1) can be measured immediately (within hours) after exposure, (2) can diagnose exposure to stressors such as estrogen mimics in an integrated fashion even within mixtures and (3) can measure bioavailability to extremely low levels of stressors. The technology being developed has the potential to be noninvasive to the sample organism and field methods have been piloted which will allow for regional characterization of stressors never before measured in the field. The technology used in these molecular analyses is readily transferable to other Regions, Federal and state agencies, and grass roots (regional/neighborhood) environmental groups.
Description:
Tetracycline and its derivatives are extensively used human and animal antibiotics, and enter stream ecosystems via point and non-point sources. Laboratory studies indicate that microbial organisms are more sensitive to antibiotics than invertebrates or fish, and may indicate the presence of antibiotics in aquatic ecosystems. We examined the consequences of tetracycline exposure to a periphyton community across a logarithmically dosed-series of experimental mesocosms receiving water from the East Fork of the Little Miami River in Milford, OH. Mesocosms were colonized naturally, dosed, and then allowed to recover, each period lasting 30 days. Target in-stream tetracycline exposures were based upon previously reported concentrations in streams and rivers throughout the United States (<1 – 100 µg L-1), and included a control. Our results indicated significant changes in the periphyton community with in-stream tetracycline concentrations as low as 0.5 µg L-1, and effects magnified in proportion with increased dosing rate, including decreases in abundance of bacteria and algae, decreased bacteria productivity, and algal compositional shifts. Recovery of the periphyton community ranged from days to several weeks depending on the organism and dosing concentration. These results suggest the potential for shifts in the trophic structure of streams after sustained (days) exposure to antibiotics.