Stream invertebrate consumer-resource stoichiometry along an urbanization gradient

Elemental imbalances between consumers and food resources have been shown to affect consumer growth and the structure and function of food web in many ecosystems.  In this study, the carbon, nitrogen, and phosphorus content of dominate stream invertebrate taxa and basal food resources (leaf litter, FBOM, periphyton, seston, filamentous algae) were determined from six streams ranging from 0-48% total watershed impervious surface area to determine the degree of imbalance between invertebrate consumers and food resources along this gradient.   There was no significant difference in the elemental composition of individual invertebrate taxa between the six streams.  However, marked differences in the elemental composition of different taxa were observed, and these differences were generally more pronounced when comparing taxa of greater taxonomic divergence.  There was considerably more variation in the elemental composition of basal food resources than in invertebrate consumers.   C: nutrient ratios in basal food resources typically increased with increasing watershed impervious surface area, resulting in increased elemental imbalances between invertebrates and food resources with increasing urbanization.  Observed increases in stoichiometric imbalances along this urbanization gradient could limit consumer growth and production in increasingly urbanized streams.