Accelerated eutrophication in Lake Titicaca: Historical evolution, mechanisms, monitoring, and observatory approach

X. LAZZARO; H. RYBARCZYK; T. MEZIANE; C. HUBAS; D. LAMY; D. POINT; J.M. MARTINEZ; S. GUÉDRON; C. DUWIG; A. GROLEAU; S. ROCHA LUPA; M.P. ALCOREZA ORTIZ; W.G. LANZA AGUIAR; A.J. FLORES; E.Z. LOYZA TORRICO; C. IBAÑEZ LUNA; J. NUÑEZ VILLALBA; C. GAMARRA PERALTA; C. VILLANUEVA QUISPE; L. LA CRUZ; V.E. VILLAFAÑE; E.W. HELBLING; A. LEBOURGES-DHAUSSY; J. GUILLARD; I. DOMAIZON; C. KRUK; N. MAZZEO; M. MEERHOFF; M. PEREIRA SANDOVAL; J. DELEGIDO; A. RUIZ; J. MORENO; C. MOLINA ARZABE; D. ACHÁ CORDERO

La Paz

Conferencia; Coloquio Internacional sobre la contaminación actual y histórica en los ecosistemas acuáticos Andinos; 2016

During 1970-1990s, deep Lago Mayor and most of shallow Lago Menor were oligotrophic with highwater transparency and strong nitrogen limitation. Greens and cyanobacteria (Anabaena) dominatedthe phytoplankton, except diatoms during the dry season, with low biomass and primary production.Windy and rainy periods drove nutrient enrichment seasonality. Discharges from Puno-Juliaca, themost populated urban center (< 350,000 inhab. in 2007) made Puno bay the most eutrophicated area,with floating Lemna proliferation. Currently, the deep pelagic areas of Lago Mayor remain oligotrophic. However, shallow littoral areas of Lago Mayor and Lago Menor are becoming meso- to eutrophic. In Lago Menor, northern littoral villages generate diffuse and point sources of human contamination, while El Alto is responsible for the overwhelming uncontrolled contamination of Cohana bay. The 2015 extended rainy season provoked the first major phytoplankton bloom event, spreading harmless green Carteria unicell over Lago Menor northern part in March-April. Anoxy killed tons of Orestias fish, giant frogs Telmatobius, and aquatic birds. Blooms have been spotted since the 2000s on images from LANDSAT satellites and NASA International Earth Observatory Orbital Station. Yet, blooms cannot be predicted because they are not studied, nor their emerging conditions. Dinoflagellate Ceratium, an invasive species in South American freshwaters favored by climate warming, and a problem for water treatment, is increasing in outer Puno bay, Lago Mayor and Lago Menor, occasionally forming blooms. Cyanobacteria Limnoraphis (syn. Lyngbya) predominate in Puno bay. Regime shifts occur between phytoplankton and macrophytes as typical in shallow lakes. Controlling accelerated eutrophication requires studying Lake Titicaca biogeochemical and ecological functioning, food web topology between plankton, fish, and macrophytes, and the drivers of regime shifts. Facing the urgency, the e-TTKK consortium is implementing a comprehensive program combining high-frequency in situ monitoring, biannual whole-lake campaigns, innovative state-of-the-art highprecision Sentinel satellite imaging, GIS GeoVisor IIGEO/UMSA, and Lake Titicaca Binational Observatory. This will improve our knowledge on Lake Titicaca eutrophication, anticipate extreme events, and advise decision makers, scientists, and the general public to take the best-coordinated actions for resources management and restoration of degraded areas, in response to global change.