PALEOLIMNOLOGICAL RESPONSE OF LAGUNA FONDOCOCHA (CAJAS NATIONAL PARK, ECUADOR) AND LAGUNA DE PIÑAN (COTACACHI CAYAPAS RESERVE, ECUADOR) TO LOCAL AND REGIONAL STRESSORS

Tropical Andean páramos are wet alpine grassland and shrub ecosystems that lie above the tree line and the below the permanent snowline (~2,800 to 4,700 m asl). They are concentrated in the northern Andes of Venezuela, Bolivia, and Ecuador where they are important regulators of the hydrologic cycle, and supply nearly all drinking water, irrigation, and hydroelectricity. These ecosystems are highly susceptible to changes in climate (e.g. temperature, wind speed) and human impacts (e.g. agriculture, grazing, mining, tourism). Ecuadorian páramos contain a relatively high density of high mountain lakes, which have been the subject of recent paleolimnological analysis. These analyses are limited by their spatial extent (restricted to southern Ecuador mainly) and their temporal extent (spanning only the last ~150 years) making broad scale conclusions difficult. Here, we analyzed two short sediment cores spanning the last 1,000 years from lakes in the northern (Piñan) and southern (Fondococha) Ecuadorian Andes with the aim of providing a longer term-perspective on ecological response to external stressors. We used diatom species relative abundance and geochemical variables (TN, TC, and δ¹³C_org) to observe changes in ecology in the sediment record. Piñan contains a dominantly benthic assemblage with shifts in dominance between Achnanthidium minutissimum sensu lato, Brachysira neoexilis, Encyonopsis c.f. krammeroides, Navicula members, Nitzschia c.f. clandestina, and Nitzschia oberheimiana. Fondococha experiences shifts in dominance between Aulacoseira distans var. septentrionalis and Aulacoseria alpigena. The lakes appear to be responding to local factors, as opposed to regional factors, highlighting that paleolimnological interpretations are context dependent.