Nutrient effects on stoichiometry in streams: an interbiome experiment

MUÑOZ, I.; CASTRO, M.; DONATO, J.; ELOSEGUI, A.; FEIJOO, C.; GARCÍA-BERTHOU, E.; GIORGI, A.; GÓMEZ, N; LEGGERI, L.; OCON, C.; RODRIGUES CAPÍTULO, A.; ROMANÍ, A.; SABATER, S.

Ciudad del Cabo

Congreso; XXXI SIL Congress; 2010

Sociedad Internacional de Limnología (SIL)

Increase of nutrient concentration is a global pressure for freshwater ecosystems impaired by the accelerated land use changes. Nutrients cause changes in elemental composition of basal resources that can extend to the whole aquatic food web. We analyzed C, N and P content of basal food resources and invertebrate and fish consumers, after experimental enhancement of N and P concentrations during 10-15 months in three streams under different biomes (a Mediterranean stream in NE Spain, a Pampean stream in Argentina, and an Andean stream in N Colombia). This whole-system experiment followed a BACI design with a control and enriched reaches studied before and after the nutrient addition. Biofilm growing on cobbles, suspended particulate organic matter and macrophytes were the basal resources with highest enrichment, particularly in P (between 35 and >100% of enrichment). The Mediterranean and the Andean streams showed the highest response due to the strong nutrient limitation in these systems. Predators and scrapers were the trophic strategies with significantly higher N and/or P content after nutrient addition in the three streams. We found large elemental imbalances (differences of elemental molar ratios) between consumers and food resources that were reduced, in some cases, after enrichment.