Stoichiometry and estimates of nutrient standing stocks of larval salamanders in Appalachian headwater streams

Abstract

Summary Because of their longevity and skeletal phosphorus demand, vertebrates can have distinct influences on the uptake, storage and recycling of nutrients in ecosystems. Quantification of body stoichiometry, combined with estimates of abundance or biomass, can provide insights into the effect of vertebrates on nutrient cycling. We measured the nutrient content and estimated the abundance and biomass of the larvae of three salamander species to characterise the factors that influence larval salamander stoichiometry and estimate the contribution of larval salamanders to nutrient standing stock and recycling in five southern Appalachian headwaters. The proportion and ratios of carbon (C), nitrogen (N), phosphorus (P) and calcium (Ca) in larval salamanders varied with size within and among species. We found negative relationships between body size and whole‐body %N, C : P and N : P and positive relationships between body size and whole‐body %P and C : N. Mean estimated larval salamander density was 58 m−2 and mean estimated dry biomass was 2813 mg m−2. Estimated standing stock of N, P and Ca were 332, 81 and 103 mg m−2, respectively, which was 1.1 × and 4.6 × greater than estimated amounts of N and P reported for macroinvertebrate taxa in similar streams within the region and was higher than in many other consumers in freshwater habitats. Using data from previous studies, we estimate that the mean ingestion rate of N and P by plethodontids is 0.000001 and 0.00001 g−1 day−1, respectively, while excretion rates of both are <0.00001 g day−1. Salamanders are the only abundant vertebrates within headwater Appalachian streams, and our results show that larval salamanders represent a large standing stock of N, P and Ca in these streams. These findings complement other recent research demonstrating the effects of larval stream salamanders on macroinvertebrate abundance and seasonal nutrient supply in Appalachian headwaters and stress the importance of plethodontid salamanders to headwater stream processes.