Larval salamander growth responds to enrichment of a nutrient poor headwater stream

While many studies have measured effects of nutrient enrichment on higher trophic levels in grazing food webs, few such studies exist for detritus-based systems. We measured effects of nitrogen and phosphorus addition on growth of larval Eurycea wilderae in a heterotrophic headwater stream using a repeated mark-recapture design. Growth estimates for 208 recaptured larvae (control stream n = 92; treatment stream n = 116) resulted in a growth rate of 0.0027 d⁻¹ in each stream prior to enrichment, whereas during enrichment treatment growth rates (g = 0.0069 d⁻¹ [±0.0019, 95% C.I.]) were significantly higher than control (g = 0.0043 d⁻¹ [±0.0007, 95% C.I.]). Results indicate that E. wilderae growth is tightly linked to the detrital resource and that growth may be indirectly affected by both quantity and quality of detritus. This study provides some of the first evidence that nutrient enrichment of detritus-based systems can influence multiple trophic levels in ways similar to autotrophic systems.