The headwaters of the Atlantic and Pacific basins extending on both sides of the Andes in Northern Patagonia TH588 born above the treeline in the high cordillera, draining mountain lakes and/or receiving directly transient streams originated in the snowpack. These systems cross barren or poorly developed soils above the timberline and areas lower in the catchment which are covered by endemic Nothofagus forests ( Paruelo et al., 1998a) to finally reach large and deep piedmont lakes ( Queimali?os et al., 2012 and Garcia et al., 2015). Andean Patagonian catchments comprise some of the most unproductive freshwater systems of the world including mountain lakes and streams. Piedmont lakes and large rivers are motor neurons characterized by limiting nutrient levels ( Pedrozo et al., 1993), extremely low DOC concentrations (< 1 mg/L) and challenging underwater UV levels ( Morris et al., 1995). These factors act concomitantly as strong driving forces for ecosystemic processes ( Marinone et al., 2006, Mladenov et al., 2011 and Queimali?os et al., 2012). For example, the harsh underwater light climate of Andean Patagonian freshwaters boosts photochemical reactions, thus influencing biogeochemical processes and certainly inhibiting the occurrence and production of aquatic organisms ( Pérez et al., 2002, Pérez et al., 2007 and Marinone et al., 2006).