Nutrient effects on stoichiometry in streams: an interbiome experiment

MUÑOZ ISABEL; CASTRO MARÍA; DONATO JOHN; FEIJOÓ CLAUDIA SILVINA; GARCÍA-BERTHOU EMILI; GIORGI ADONIS DAVID NAZARENO; GÓMEZ NORA; LEGGIERI LEONARDO RAMÓN; OCÓN CAROLINA; RODRIGUES-CAPÍTULO ALBERTO; ROMANÍ ANNA; SABATER SERGI

Ciudad del Cabo

Congreso; XXXI Congress of the International Limnology Society (SIL); 2010

Increase of nutrient concentration is a global pressure for freshwater ecosystems impaired by the accelerated land use changes. Ecological Stoichiometry considers the relative balance of key elements (CNP) in trophic interactions. Changes in nutrient inputs can cause changes in elemental composition of basal resources that can extend to the whole aquatic food web. The amplitude of the response will depend on site-specific environmental conditions (light, temperature, hydrology, nutrient condition, food web structure).The objectives of this study were: a) to contrast the effects of nutrient enrichment on elemental composition of basal sources, and how this enrichment affected the elemental composition of higher trophic levels and b) to test these effects in streams from different bioclimatic regions. Three streams under different biomes (a Mediterranean stream in NE Spain, a Pampean stream in Argentina, and an Andean stream in N Colombia). The systems had the same stream order but had specific temperature, background nutrient levels, light and discharge. Basal food resources in the studied streams had very low nutrient content. C:P and N:P ratios were high compared with other food webs (terrestrial, planktonic). There was an important imbalance between resources and consumers in the three streams. Nutrient inputs contribute to diminished it but not in all the compartments. The highest reduction was observed in C:P ratios.