Direct and interactive effects of ecologically relevant concentrations of organic wastewater contaminants on Rana pipiens tadpoles

Organic wastewater contaminants (OWCs) have recently been documented in several aquatic ecosystems. We examined the effects of three OWCs (caffeine, acetaminophen, and triclosan) on the activity level, startle response, survivorship, and growth of northern leopard frog (Rana pipiens) tadpoles. We conducted two experiments: one on the effects of acetaminophen and triclosan alone and in combination, and the other on the effects of caffeine and acetaminophen alone and in combination. In both experiments acetaminophen had no effect on activity, startle response, survivorship, or final mass. In experiment 1, tadpoles exposed to triclosan were less active than controls. Tadpoles exposed to the highest triclosan concentration had lower startle response and survivorship than in the other concentrations and in the control. Tadpoles exposed to the intermediate triclosan concentrations were heavier than in other treatments, but not in the control. In experiment 2, tadpoles exposed to the highest caffeine concentration were the most active. Acetaminophen increased the effect of caffeine on activity. More tadpoles exposed to caffeine exhibited a startle response than did control tadpoles. Survivorship was 100% for all caffeine treatments. There was a tendency (P = 0.06) for tadpoles exposed to higher concentrations of caffeine to be smaller. In general, the interactive effects were not important. Our results show that ecologically relevant levels of some OWCs can have both behavioral and physiological effects on R. pipiens tadpoles. Thus, amphibians may be affected by exposure to levels of OWCs that appear to be widespread in aquatic ecosystems. (C) 2004 Wiley Periodicals, Inc.