Fossil pigments and environmental conditions in the oligotrophic Laja Lake in the Chilean Andes
Résumé
Interactions among climate change, ozone depletion, and ultraviolet radiation affect aquatic ecosystems.
Meteorological and biological monitoring is often too brief, however, to record the magnitudes of past changes in
ultraviolet fluxes and their effects. This study presents an analysis of fossil pigments and environmental conditions
in the oligotrophic Laja Lake in the Chilean Andes over a 60-year period. The age of the sediment core was
determined using high-efficiency gamma spectrometry and dated with lead-210 (210Pb). Analysis of the total and
specific fossil pigments from a sediment core utilized a combination of analytical methods, spectrophotometry,
and high-performance liquid chromatography. Environmental variables, such as stratospheric ozone concentration,
temperature, precipitation, and ultraviolet radiation explained changes in the fossil pigment scytonemin..
Results showed that low cloud cover over the high mountain lake predominated, with high ultraviolet radiation
and temperature values during summer months. The most abundant group was Bacillariophyceae (diatoms). The
highest concentrations of the pigments (canthaxanthin echinenone, myxoxanthophyll, aphanizophyll zeaxanthin and
scytonemin) that represent the cyanobacteria groups were found in the upper part of the core (cm 0–15). The
trend analysis further suggested that the influence of environmental features enabled generation of ultraviolet
radiation-shielding pigment in the algae communities in the high mountain lake.This study advances understanding
of the interactive effects of climate change, ozone depletion, and ultraviolet radiation on aquatic
ecosystems. Fossil pigments proved to be good indicators of lake-ecosystem response to climate/environmental
changes, which are necessary for predicting possible effects of future climate change.