SPECTRAL COMPOSITION OF THE AQUATIC LIGHTFIELD OF THE LAKES RINIHUE, TODOS-LOS-SANTOS, LAGUNA-NEGRA AND EL-YESO RESERVOIR

Measurements of the spectral attenuation of underwater light in four c hilean lakes using a submersible spectroradiometer are reported. For a ll waterbodies, the attenuation of light in the red region (600-700 nm waveband) is much more important than that in the blue region as know n for waterbodies with low yellow substances. Apart from the El Yeso R eservoir, where an important input of gypsum takes place, this attenua tion is mainly due to the water itself. For the three more transparent lakes, below 10m depth, more light is available for the wavelength ra nge measured with the sensor ''670nm'' than expected for pure water. F or these deeper layer, extinction coefficients for 670nm between 0.2m- 1 and 0.3m-1 were found. Comparison with pure water (a(water) = 0.43m- 1) suggests that natural fluorescence of chlorophyll is involved. The possible participation of chlorophyll natural fluorescence in the abov e described phenomenon is discussed.