Landscape integration of North Patagonian mountain lakes: a first approach using the characterization of dissolved organic matter

GARCÍA, PE; DIÉGUEZ, MC; QUEIMALIÑOS, CP

LAKES & RESERVOIRS RESEARCH AND MANAGEMENT

Wiley Online Library

Año: 2015 vol. 20 p. 19 - 32

1320-5331

North-western Patagonia has a variety of glacially formed mountain lakes occurring at different positions from the treeline in the Andean Patagonian forest region. We analyzed water chemistry of six North Patagonian lakes located in an altitudinal gradient, above, at and below the treeline (~41°S). We addressed the relative importance of allochthonous to autochthonous carbon inputs along a marked catchment vegetation gradient encompassing altoandino vegetation and Nothofagus forests. Dissolved organic carbon (DOC) varied among lakes; with lakes higher in the landscape presenting lower DOC (2 mg L-1). The analysis of coloured and fluorescent dissolved organic matter (CDOM and FDOM, respectively) followed the DOC pattern, despite their contrasting catchments. The results indicated that the CDOM in all the lakes has low molecular weight and low aromaticity. The Excitation Emission Matrices EEMs showed three distinctive fluorophores in the FDOM: two humic-like (peak A and peak C) revealing the presence of humic terrestrial material, and a protein-like fluorophore (peak T) generally associated to autochthonous DOM. The increase in the intensities of the humic fluorophores in the lakes located below the treeline suggests higher allochthonous carbon inputs from the catchment. Collectively, this evidence suggests that in terms of DOM, mountain lakes show some heterogeneity, likely due to their position in relation to the treeline which determines the contribution of the catchment. As remote lakes are extremely sensitive to changes in the catchment, these North Patagonian mountain lakes may accurately track the impact of climate and anthropogenic changes on the landscape.