Tadpole species have variable roles in litter breakdown, sediment removal, and nutrient cycling in a tropical stream

Quantifying the influence of biodiversity on ecosystem function is an increasingly important goal as biodiversity declines. Tadpoles can be important contributors to ecosystem processes in streams, so amphibian declines over recent decades may have far-reaching ecosystem effects. We, therefore, used artificial channels located near an Australian rainforest stream to assess how the tadpoles of 2 frog species affect leaf litter decay, sediment bioturbation, and nutrient cycling in the presence and absence of invertebrates. Mixophyes coggeri (Myobatrachidae) tadpoles did not increase leaf mass loss, but were important in sediment removal, which benefits smaller consumers. In contrast, high densities of Litoria serrata (Hylidae) tadpoles increased leaf mass loss, possibly because their excretion of nutrients facilitated decomposition, but were not important in sediment removal. However, we found no effect of nutrient excretion by L. serrata tadpoles on the nutrient quality of leaves and sediments, or on biofilm growth, even though L. serrata tadpoles and invertebrates together appeared to remove significant quantities of nutrients from sediment. Our results show that tadpoles of different species can have different functional roles in the ecosystem, which need to be taken into account when assessing the influence of amphibian declines on ecosystem processes