Ecological Risk Assessment of Urban Streams Using Fish Biomarkers of DNA Damage and Physiological Responses

Ecological risk assessment was carried out in two urban streams, viz. Gap Stream (GS) and Miho Stream (MS), in the Geum River Watershed during July 2013-October 2014. The techniques used in this study included multi-level fish biomarkers of DNA damage based on single-cell gel electrophoresis (SCGE) coupled with the study of physiological responses based on 7-ethoxyresorufin-O-deethylase (EROD) and acetylcholinesterase (AChE) activities in fish species. Biomarker values of tail DNA (tDNA), tail length (T-L), and tail extent moment (TEM) in impacted zone (I-z) were 2.0-3.6-fold greater than in controls (C-z). Nucleus image analysis showed that the nucleus had circular particle forms in the C-z as compared with a longitudinal oval form with broken particles from the nucleus in the I-z. Physiological response analysis of EROD and AchE activities indicated that their levels were higher in the I-z than in the C-z. Such DNA damages and greater physiological responses in the I-z were attributed to chemical contaminants discharged from the wastewater disposal plants and industrial complex. This combination of DNA damage and physiological responses approach can be used as a key tool for early-warning detection of chemical contaminants and concomitant risks to the ecological health of urban streams.