The first two-year high-frequency sensor data on the interactive effects of vertical mixing, ultraviolet and visible (PAR) radiation, and phytoplankton fluorescence from Lake Titicaca (Bolivia)

LAZZARO, X.; ROCHA,S.; ACHA, D.; POINT, D.; GROLEAU,A.; RYBARCZYK, H; VILLAFAÑE, V. E.; HELBLING, E. W.

Ginebra

Simposio; 9th Symposium for European Freshwater Sciences; 2015

LakeTiticaca, the world largest tropical high-altitude (3.810 m asl) freshwaterlake is already altered by eutrophication, pollution, and climate change. Surprisingly,it has been poorly studied over the last two decades, and never surveyed. Increasingorganic matter inputs benefit phytoplankton by attenuating the penetration ofsolar radiation, including damaging ultraviolet, and PAR useful forphotosynthesis. Vertical mixing confounds since cells are exposed to fluctuatingradiation regimes. To explore the relationships between solar radiationattenuation and phytoplankton fluorescence (a relative proxy of chlorophyll), weimplemented the first 2-year continuous high-frequency in situ sensor monitoring at Huatajata, shallow polymictic. Toanalyze how vertical mixing interferes, we coupled a vertical profiling at Huatajata,and Chúa, deep monomictic, every 18 days. We found (a) positive relationshipsbetween total fluorescence, daily PAR dose, and wind velocity; (b) lowerfluorescence maxima and higher attenuation coefficient at Huatajata; (c) weaksurface fluorescence attenuation at Huatajata, and 80% attenuation with deepchlorophyll-a maxima at Chúa; (d)strong diurnal fluorescence fluctuation with nocturnal maxima, with highfluorescence periods not clearly related to seasons but intense irradiance. High-frequencydata can be extrapolated to validate models for improving the understanding andprediction of Lake Titicaca processes facing global changes.