The Role of Bullfrog Tadpoles (Rana catesbeiana) on Stream Ecosystem Dynamics BIOS 35502: Practicum in Environmental Field Biology

Amphibians, widely studied as environmental indicators, facilitate the transfer of nutrients between aquatic and terrestrial habitats. To examine the role of amphibians in nutrient cycling, I studied bullfrog (Rana catesbeiana) tadpoles in an artificial stream environment. I hypothesized that the presence of tadpoles would decrease algal stock biomass and sedimentation but increase chlorophyll a production. To test these predictions, I subjected artificial streams to three treatments: live tadpoles, dead tadpoles, or no tadpoles (control), and monitored their effects on algal biomass, sedimentation and chlorophyll a concentration over time. I found that the streams containing living tadpoles had significantly higher chlorophyll a content when compared to the other treatments. However, neither the sedimentation nor algal hypotheses were supported, partly because nonlinear dynamics affected the analysis and understand of the variables. I discuss multiple scenarios that suggest the environment’s ability to affect the role of tadpoles in stream ecology. Introduction The decline of amphibians in Central America, the United States, and southern Canada may be correlated with increased logging, climate changes involving increases in ultraviolet B radiation, and habitat destruction (Kiffney and Richardson 2001, Green 2003). Amphibians, specifically frogs and toads (anurans), are prime indicators of ecological changes due to their high