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Reinforcement of Knowledge of Some Parameters of Lake Itasy in Order to Establish Its Current State of Health

2020; Volume: 10; Issue: 2 Linguagem: Inglês

2163-2634

Rija I. Rakotonirina, Jerry J. C. F. Randrianiaina, F. Lahatra Razafindramisa,

Aquatic Ecosystems and Biodiversity

The main purpose of this work is to assess the current state of Lake Itasy, the third largest lake in Madagascar. Temperature, pH, electrical conductivity, dissolved oxygen and oxygen saturation are the parameters monitored from October 2017 to October 2019. The temperatures observed are from 18.1°C to 30.3°C with a mean 23.1 3.07°C; the electrical conductivities are from 42.2µS.cm-1 to 76.4µS.cm-1 with a mean 58.94 8.40 µS.cm-1; the pH measured is from 7.16 to 8.31 with a mean 7.76 0.31; the dissolved oxygen contents are from 4.0 mg.L-1 to 9.7 mg.L-1 with a mean 7.8 1.08 mg.L-1, the oxygen saturations are from 51% to 113% with a mean 90 12%. Comparison of these current values with fifty years before shows slight changes in the state of the lake; temperature and pH increase while the electrical conductivity decrease. However, the current values remain largely within the established standards for surface and freshwater in general. The second part of the work is devoted to understanding the seasonal evolution of these five parameters. A multivariate statistical analysis show that different behaviours are observed for this lake depending on whether it is in the rainy season, in the dry and cold season or in the hot season.