Global declines of amphibian populations are well-documented, yet long-term ecosystem-level effects of these losses are poorly understood.  Grazing amphibian larvae have the potential to alter stream algal communities and seston, particularly in the tropics where amphibian abundance and diversity are high. As part of the Tropical Amphibian Declines in Streams (TADS) Project, we examined changes of algal periphyton and seston quality and quantity in two upland Panamanian streams in response to a disease related catastrophic die-off of stream-breeding frogs.  One stream had no tadpoles as a result of a decline 10 years prior to the start of the study, and the other stream had a healthy population of amphibians at the start, although suffered a widespread amphibian extirpation 18 months into the study.  

Results/Conclusions

Monthly sampling of natural stream substrate at the previously "healthy" stream showed significantly increased levels of chlorophyll a (+180%), ash-free dry mass (+210%), and inorganic sediments (+160%) during the 36 month post-extirpation period relative to pre-extirpation (18 months).  Periphyton δ15N decreased post-extirpation, suggesting a change in the source of N for uptake by algae.  Algal %P decreased and C/P increased after the decline at the "healthy" stream.  Seston quality decreased, as evidenced by a higher C/N ratio.  Our data indicate that stream-dwelling tadpoles  decrease the quantity yet increase the quality of periphyton, and increase both quantity and quality of seston.  Results also show that effects of tadpole losses on stream ecosystems may persist for years.