Linking landscape heterogeneity with lake dissolved organic matter properties assessed through absorbance and fluorescence spectroscopy: Spatial and seasonal patterns in temperate lakes of Southern Andes (Patagonia, Argentina)

QUEIMALIÑOS, CLAUDIA; REISSIG, MARIANA; PÉREZ, GONZALO L.; SOTO CÁRDENAS, CAROLINA; GEREA, MARINA; GARCIA, PATRICIA E.; GARCÍA, DANIEL; DIÉGUEZ, MARÍA C.

THE SCIENCE OF TOTAL ENVIRONMENT

Elsevier Science BV

Año: 2019 vol. 686 p. 223 - 235

0048-9697

Hydrological connectivity between terrestrial and aquatic systems is influenced by landscape features. Topography, vegetation cover and type, lake morphometry and climate (seasonality, precipitation) drive the timing, con-centration and quality of allochthonous dissolved organic matter (DOM) inputs to lakes, influencing lakemetabolism. The impact of climate changes on terrestrial-aquatic linkages depends on regional trends and eco-systems properties. We examined how landscape heterogeneity affects lake DOM in pristine temperate headwa-ter lakes located in sharp bioclimatic gradients at the leeward side of the southern Andes (Patagonia, Argentina),and predicted their potentialresponsesto forecasted changes in regional climate. Weassessed DOM properties ofdeep and shallow lakes spotted along precipitation and altitudinal gradients which reflect on vegetation hetero-geneity. Lake DOM (concentration, and chromophoric andfluorescent properties) was related to terrestrial bio-climatic conditions, addressing also DOM bio- and photodegradation processes. Co-effects of climate andvegetation determined the quantity and quality of allochthonous DOM inputs. Higher terrestrial signs showedup at the wettest extreme of the gradient and during the rainy season, being attributable to higher hydrological land-water connectivity, and dense vegetation cover. Under drier conditions, DOM displayed higherphotobleaching signs at spatial and temporal scales. The ratio between non-humic and terrestrial humic sub-stances indicated that DOM biodegradation dominates in shallow forested lakes and photodegradation prevailsin deep ones, whereas coupled photo- and biological processing shaped the DOM pool of high altitude lakes.Overall, DOM optical metrics captured landscape heterogeneity. Under the forecasted climate changes for Pata-gonia (decreasing precipitation and increasing temperature), piedmont lakes may experience lower hydrologicalconnectivity, lower terrestrial inputs and, enhanced photobleaching usually associated with longer water resi-dence time. In high altitude lakes, terrestrial DOM inputs are expected to increase due to the upward expansionof native deciduous forests, thus becoming more similar to lakes located lower in the landscape.