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

Año: 2019 vol. 686 p. 223 - 235

0048-9697

Hydrological connectivity between terrestrial and aquaticsystems is influenced by landscape features. Topography, vegetation coverand type, lake morphometry and climate (seasonality, precipitation) drivethe timing, concentration and quality of allochthonous dissolved organicmatter (DOM) inputs to lakes, influencing lake metabolism. The impact ofclimate changes on terrestrial-aquatic linkages depends on regionaltrends and ecosystems properties. We examined how landscape heterogeneityaffects lake DOM in pristine temperate headwater lakes located in sharpbioclimatic gradients at the leeward side of the southern Andes(Patagonia, Argentina), and predicted their potential responses toforecasted changes in regional climate. We assessed DOM properties ofdeep and shallow lakes spotted along precipitation and altitudinalgradients which reflect on vegetation heterogeneity. Lake DOM(concentration, and chromophoric and fluorescent properties) was relatedto terrestrial bioclimatic conditions, addressing also DOM bio- andphotodegradation processes. Co-effects of climate and vegetationdetermined the quantity and quality of allochthonous DOM inputs. Higherterrestrial signs showed up at the wettest extreme of the gradient andduring the rainy season, being attributable to higher hydrological landwaterconnectivity, and dense vegetation cover. Under drier conditions,DOM displayed higher photobleaching signs at spatial and temporal scales.The ratio between non-humic and terrestrial humic substances indicatedthat DOM biodegradation dominates in shallow forested lakes andphotodegradation prevails in deep ones, whereas coupled photo- andbiological processing shaped the DOM pool of high altitude lakes.Overall, DOM optical metrics captured landscape heterogeneity. Under theforecasted climate changes for Patagonia (decreasing precipitation andincreasing temperature), piedmont lakes may experience lower hydrologicalconnectivity, lower terrestrial inputs and, enhanced photobleachingusually associated with longer water residence time. In high altitudelakes, terrestrial DOM inputs are expected to increase due to the upwardexpansion of native deciduous forests, thus becoming more similar tolakes located lower in the landscape.