Stable isotope analysis of trophic structure, energy flow and spatial variability in a large ultraoligotrophic lake in Northwest Patagonia

ARCAGNI MARINA; RIZZO, ANDREA; CAMPBELL LINDA M.; ARRIBÉRE MARÍA; JUNCOS, ROMINA; REISSIG, MARIANA; KYSER, KURT; BARRIGA JUAN PABLO; BATTINI, MIGUEL; RIBEIRO GUEVARA SERGIO

JOURNAL OF GREAT LAKES RESEARCH

ELSEVIER SCI LTD

Año: 2015 vol. 41 p. 916 - 925

0380-1330

The food web structure of the largest lake in northwest Patagonia, Lake Nahuel Huapi, was investigated. Fish, benthic macroinvertebrates, biofilm, plankton, and terrestrial material were analyzed for stable nitrogen (δ15N) and carbon (δ1335 C) isotopes in three sites with contrasting morphometry and environmental characteristics. The δ1536 N values indicated that introduced salmonids and native creole perch share the highest trophic level in the three sites, while potential prey such as macroinvertebrates and smaller fish species are in a lower trophic level. As expected, primary producers (e.g. phytoplankton and biofilm) had the lowest δ1539 N values. SIAR (Stable Isotope Analysis in R) mixing model was used to study potential food sources (benthic or pelagic) for adult fish, and the results were compared with published gut content analysis. According to the model, in two sites (Brazo Rincón and Bahía López) of Lake Nahuel Huapi, pelagic sources, represented by the native small fish Galaxias maculatus, were more important for the consumer?s diet than benthic sources (crayfish Samastacus spinifrons). On the contrary, in the third site (Dina Huapi), the trend was the opposite. An ontogenetic shift in the carbon source and trophic level was observed in some of the fish species, revealing a coupling between the pelagic and bentho-littoral habitats of the lake.