DOES THE STOICHIOMETRIC CARBON:PHOSPHORUS KNIFE EDGE APPLY FOR PREDACEOUS COPEPODS?

CECILIA LASPOUMADERES; BEATRIZ MODENUTTI; JAMES ELSER; ESTEBAN BALSEIRO

Granada

Congreso; ASLO 2015 - Aquatic Sciences Meeting; 2015

ASLO (Asociation for the Sciences of Limnology and Oceanography)

Stoichiometric food quality in terms of carbon:phosphorus (C:P) ratios affects consumers whether the imbalance involves a deficit or an excess of nutrients; hence, organisms exist on a ?stoichiometric knife edge?. While studies have focused primarily on autotroph-herbivore trophic transfer, nutritional imbalances might also affect species interactions at higher trophic levels. Since carnivores? foods are normally stoichiometrically similar to their own body composition, they may be more severely affected than herbivores if imbalances become pronounced. We analysed the response of a predatory copepod to monospecific diet treatments consisting of high and low C:P prey items. These dietary treatments strongly affected the predators? elemental composition and growth, although prey selection, excretion, egestion, and respiration rates were not affected. We suggest that, due to their low threshold elemental ratio and a narrow C:P stoichiometric knife edge, these predators are highly vulnerable to stoichiometric imbalances, whether an excess or a deficit of nutrients is involved. Our results thus show that the stoichiometric knife edge applies not only to herbivores but also to higher trophic levels.