Oxygen flux as an indicator of physiological stress in fathead minnow (Pimephales promelas) embryos:: A real-time biomonitoring system of water quality

The detection of harmful chemicals and biological agents in real time is a critical need for protecting freshwater ecosystems. We studied the real-time effects of five environmental contaminants with differing modes of action (atrazine, cadmium chloride, pentachlorophenol, malathion, and potassium cyanide) on respiratory oxygen consumption in 2-day postfertilization fathead minnow (Pimephales promelas) eggs. Our objective was to assess the sensitivity of fathead minnow eggs using the self-referencing micro-optrode technique to detect instantaneous changes in oxygen consumption after brief exposures to low concentrations of contaminants. Oxygen consumption data indicated that the technique is indeed sensitive enough to reliably detect physiological alterations induced by four of the five contaminants. After 2 h of exposure, we identified significant increases in oxygen consumption upon exposure to pentachlorophenol (100 and 1000 mu g/L), cadmium chloride (0.0002 and 0.002 mu g/L), and atrazine (150 mu g/L). In contrast, we observed a significant decrease in oxygen flux after exposures to potassium cyanide (44 and 66 mu g/L) and atrazine (1500 mu g/L). No effects were detected after exposures to malathion (200 and 340 mu g/L). Our work is the first step in development of a new technique for physiologically coupled biomonitoring as a sensitive and reliable tool for the detection of environmental toxicants.