Influences of Catastrophic Amphibian Declines on Storage and Export of Fine Particulate Organic Matter in Neotropical Headwater Streams

Larval amphibians can be important in tropical streams because their feeding and egestion can enhance food availability to other consumers. As part of the Tropical Amphibian Declines in Streams (TADS) project, we are examining the long-term ecological consequences of stream-breeding amphibian extirpations in the Panamanian Highlands. We sampled fine (<1mm,>250 μm) and very fine (250μm) benthic organic matter and organic seston (,754 μm) for multiple years in streams at El Cope, where a recent amphibian decline occurred, and Fortuna, which declined over a decade ago. In El Cope streams, post-decline benthic organic matter standing stocks remained similar to pre-decline (74.5 and 73.4 gAFDM/m2, respectively). Organic seston C/N in Fortuna streams averaged 10.4, while El Cope increased from 9.0 (pre-decline) to 10.6 (post-decline). At El Cope, base flow organic seston concentrations decreased from 2.7mg L-1 (predecline) to 1.4mg L-1 (post-decline). Increased C/N and lower concentrations of seston indicate that amphibian declines alter the quantity and quality of organic materials exported from tropical headwater streams, but may not affect benthic organic matter standing stocks, at least within the time frames we examined.