Monday, May 26, 2008 - 5:00 PM
112

Landscape variation in stream phosphorus alters consumer-resource stoichiometry in lowland neotropical streams

Gaston E. Small IV and Catherine M. Pringle. Odum School of Ecology, University of Georgia, Athens, GA 30602-2202

Nutrient enrichment in stream ecosystems has the potential to affect trophic relationships by altering the balance in elemental composition between consumers and their food resources.  Ecological stoichiometry predicts that elemental ratios of consumer species are relatively fixed (homeostatic), while elemental composition of basal food resources may vary with nutrient availability.  We measured stoichiometric flexibility in basal food resources by analyzing carbon (C), nitrogen (N), and phosphorus (P) content of leaf litter and epilithon from a series of streams in lowland Costa Rica that range widely in P-levels (2-135 µg/L soluble reactive phosphorus) due to natural inputs of solute-rich groundwater.  We also compared stoichiometric relationships between basal food resources and invertebrate consumers in two streams on opposite ends of this P-gradient.  Leaf litter and epilithon P-content increased linearly with stream P-levels, exceeding published values from other nutrient-enriched streams.  Invertebrate consumers in the P-rich stream increased on average two-fold in P-content, across multiple taxonomic and functional feeding groups.  Highly P-enriched basal food resources potentially alleviate P-limited growth by benthic consumers.  Elevated P-content in consumers may result in more P reaching higher trophic levels and a greater flux of P exported to the terrestrial food web through insect emergence.


Web Page: Ecological Stoichiometry, phosphorus

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