Leaf-litter stoichiometry is affected by streamwater phosphorus concentrations and litter type

The stoichiometric ratios of organisms and their food resources can influence C and nutrient dynamics in aquatic ecosystems. Several investigators have quantified linkages between nutrient enrichment and consumer stoichiometry for stream detritivores, but very few have systematically quantified the effect of P enrichment on leaf-litter stoichiometry. Here, we examine the potential stoichiometric changes of 2 species of leaf litter subjected to varying levels of P enrichment in laboratory microcosms and mixed species across a natural P gradient of streams in the Ozark Highlands Region, Arkansas, USA. Leaf-litter %P content increased and C:P ratios decreased with increasing levels of P enrichment and with increasing lability of the leaf species. In the laboratory study, C:P of maple and oak leaves in the control treatment was ,2500, whereas this ratio decreased to 500 and 1000 in the high-P treatments, respectively. Total P (TP) was inversely related to leaf-litter C:P along the natural P gradient of streams in the Ozarks. Our results add to the growing body of information on the potential bottom-up effects of anthropogenic nutrient loading in streams and the influence of water-column nutrients and leaf quality on this response.