Spatio-temporal analysis of chlorophyll in six Araucanian lakes of Central-South Chile from Landsat imagery

Chlorophyll-a (Chl-a) is an optically active compound commonly used as a proxy for phytoplankton biomass and trophic state in an aquatic system. This work aimed to analyze the spatiotemporal variation of Chl-a values in six Araucanian lakes in Central-South Chile. Here we combined in-situ Chl-a measurements and thirteen Landsat 8 satellite images to build a set of the linear and non-linear models to estimate Chl-a values in the lakes. Through the Taylor diagram, r Pearson, standard deviation, and other statistical indicators (R2, RMSE, IA, and MBE) the Chl-a models were validated. A qualitative/quantitative analysis to identify the species of microalgae present in the lacustrine systems was used. Next, Chl-a estimation maps were created to understand the spatial and seasonal behavior of this variable in each aquatic ecosystem. We observed that during the Summer months the Chl-a values are higher than in the Spring months for all lakes, except in Pirehueico lake. Moreover, the Chl-a models created predict with high accuracy, the results of statistical indicators are R2 ≥ 0.94, IA ≥ 0.80, RMSE ≤0.214 μg/L, and MBE ≤ −0.123 μg/L. In the lake systems were found two invasive species, C. hirundinella, and Didymosphenia geminata, species recognized as bloom-forming in other aquatic systems. Finally, the Chl-a maps provided information on the monitoring of areas sensitive to Chl-a changes. This study is very important to conserve the water quality and early alert to forming phenomena like algal blooms which contributes to providing useful data for managers and policy-makers in Chilean lakes.