Food web structure in a double-basin ultra-oligotrophic lake in Northwest Patagonia, Argentina, using carbon and nitrogen stable isotopes.

ARCAGNI M.; CAMPBELL L.; ARRIBERE M.; KYSER K.; KLASSEN K.; CASAUX R.; MISERENDINO L.; RIBEIRO GUEVARA S.

LIMNOLOGICA

ELSEVIER GMBH

Año: 2012 vol. 32 p. 131 - 142

0075-9511

a b s t r a c tFish, benthic macroinvertebrates, macrophytes, biofilm, plankton, and terrestrial material were analyzedfor stable nitrogen (15N) and carbon isotopes (13C) to study the food web structure of a double-basined,ultra-oligotrophic lake in northwest Patagonia. The 15N values of all biota were consistently higher inMoreno East basin, probably caused by a higher anthropogenic impact; however, the estimated trophicpositions of fish showed no differences between basins, indicating that fish are feeding from food chainswith different 15N baselines. Fish 13C values were higher in Moreno West basin but no pattern wasobserved for the rest of the organisms analyzed. The different hydrogeomorphic characteristics betweenthe basins could lead to these differences in the C signatures of fish. SIAR (Stable Isotope Analysis in R)mixing model was used to study possible food sources for adult fish and the results were contrasted withpublished gut content analysis. According to the model, in both basins small size fish such as Small Puyen(Galaxias maculatus) and juvenile fish, had the highest relative isotopic contribution to introduced RainbowTrout (Oncorhynchus mykiss) and Brook Trout (Salvelinus fontinalis), which had lower contributionsfrom other sources such as insect larvae, decapods, and snails. On the contrary, decapods and insect larvaewere isotopically more important for the native Creole Perch (Percichthys trucha) than small fish inboth basins. An ontogenetic shift in the carbon source and trophic level was observed in Puyen Chico andRainbow Trout from the West basin.