RODRIGUES CAPITULO Alberto
Global pressures, specific responses: effects of nutrient enrichment in streams from different biomes
ARTIGAS, J.; EMILI GARCÍA-BERTHOU ; BAUER; MARIA I. CASTRO; UNIVERSIDAD DE GIRONA / INSTITUTO DE ECOLOGIA ACUATICA; JOAQUÍN COCHERO; DR. ALBERTO RODRIGUES CAPITULO; CORTELESSI, A.; GOMEZ, N; SABATER, S.
ENVIRONMENTAL RESEARCH LETTERS
IOP PUBLISHING LTD
Lugar: Londres; Año: 2012 vol. 8 p. 1 - 13
Abstract We assessed the effects of nutrient enrichment on three stream ecosystems running through distinct biomes (Mediterranean, Pampean and Andean). We increased concentrations of N and P in stream water 1.6 to 4-fold following a Before-After Control-Impact Paired Series (BACIPS) design in each 31 stream, and evaluated changes in the biomass of bacteria, primary producers, invertebrates, and fish 32 in the enriched (E) versus control (C) reaches after nutrient addition through a predictive BACIPS 33 approach. The treatment produced variable biomass responses (2-77 % of explained variance) 34 among biological communities and streams. The greatest biomass response was observed for algae 35 in the Andean stream (77 % of the variance), although fish also showed important biomass 36 responses (ca. 9-48 %). The strongest biomass response to enrichment (77 % in all biological 37 compartments) was found in the Andean stream. The magnitude and seasonality of biomass 38 responses to enrichment were highly site-specific, often depending on the basal nutrient 39 concentration and on windows of ecological opportunity (periods when environmental constraints 40 other than nutrients do not limit biomass growth). The Pampean stream, with high basal nutrient 41 concentrations, showed a weak response to enrichment (except for invertebrates), whereas the 42 greater responses of Andean stream communities were presumably favored by wider windows of 43 ecological opportunity in comparison to those from the Mediterranean stream. Despite variation 44 among sites, enrichment globally stimulated the algal-based food webs (algae and invertebrate 45 grazers) but not the detritus-based food webs (bacteria and invertebrate shredders). The present 46 study shows that nutrient enrichment tends to globally enhance the biomass of stream biological 47 assemblages, but that its magnitude and extent within the food web is complex and strongly 48 determined by environmental factors and ecosystem structure.