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Temporal dynamics of periphyton exposed to tetracycline in stream mesocosms
QUINLAN, E. L., C. T. NIETCH, K. A. BLOCKSOM, J. M. LAZORCHAK, A. BATT, R. A. GRIFFITHS, AND D. KLEMM. Temporal dynamics of periphyton exposed to tetracycline in stream mesocosms. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 45(11):10684-10690, (2011).
Significant amounts of antibiotics enter the environment via point and non-point sources. We examined the temporal dynamics of tetracycline exposure to stream periphyton and associated organisms across a logarithmically dosed series of experimental mesocosms, designed to mimic natural conditions. Target in-stream tetracycline exposures were based on environmentally-relevant concentrations in aquatic ecosystems throughout the United States. Significant changes in the stream biotic community were observed within 7 days with in-stream tetracycline concentrations as low as 0.5 ug L-1, including significant changes in bacteria abundance and productivity, algae biomass, cyanobacteria, organic biomass, nematodes and macroinvertebrates. These effects were magnified with increased exposure time and dosing concentration. Recovery of the periphyton community after 28 days of exposure was dependent upon the tetracycline dose. At the highest doses, bacteria productivity recovered; however, bacteria, algae and nematode abundance did not recover at the same rate, and remained low even after a 28-day recovery period (of non-dosing). This study is the first to demonstrate that a common antibiotic at currently-detected concentrations in the environment can affect stream periphyton structure with potential consequences for higher trophic levels and stream ecosystem function.
A great deal of uncertainty exists regarding the extent to which humans and wildlife are exposed to chemical stressors in aquatic resources. Scientific literature is replete with studies of xenobiotics in surface waters, including a recent national USGS survey of endocrine disrupting chemicals; however, biological significance of these chemical data is in question since chemical bioavailability is largely unknown and biological events may be induced by undetected chemicals and varying ecological conditions (i.e., total nitrogen and phosphorus). Whole effluent toxicity data exist, but do not answer specific exposure questions that may support detailed ecological risk assessments. Interpretation of data arising from exposure to complex chemical mixtures is even more problematic. A solution to these problems is development of sensitive and specific cellular indicators of exposure in aquatic organisms. The potential for development is enhanced by emergent resources in molecular biology and associated technologies, most notably DNA microarrays consisting of transcriptionally relevant nucleic acid sequences that can be used to detect altered gene expression in cells, tissues and various life stages of organisms exposed to chemical and natural stressors.
Record Details:Record Type: DOCUMENT (JOURNAL/PEER REVIEWED JOURNAL)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL EXPOSURE RESEARCH LAB
ECOLOGICAL EXPOSURE RESEARCH DIVISION
ECOSYSTEMS RESEARCH BRANCH