Simulation of water colors in a shallow acidified lake, Lake Onneto, Japan, using colorimetric analysis and bio-optical modeling

• Published in: Limnology Vol. 10; no. 1; pp. 47 - 56
• Main Authors: Oyama, Yoichi, Shibahara, Akihiko
• Format: Journal Article
• Language: English
• Published: Japan Japan : Springer Japan 01.04.2009; Springer Japan; Springer Nature B.V
• Subjects: Biomedical and Life Sciences; Color; Ecology; Environment; Freshwater; Freshwater & Marine Ecology; Lakes; Life Sciences; Limnology; Optical properties; Research Paper; Scattering; Sediments; Japan; Bottom sediments; Absorption; Water color; Scattering
• ISSN: 1439-8621; 1439-863X
• DOI: 10.1007/s10201-009-0260-1

Lake Onneto has unusually brilliant water colors, such as blue-green, green, and greenish yellow. We investigated the coloration mechanism in this lake by measuring the radiometric water color and inherent optical properties (IOPs), such as attenuation, absorption, and scattering coefficients of color-producing agents (CPAs) in the lake. The hue of the water body was determined using colorimetric analysis. In addition, the radiometric water color of the lake was simulated using bio-optical modeling. Results showed that the hues of the water body were different between two sampling stations (blue-green and green at 3.1 and 5.5 m of bottom depth, respectively). However, the total suspended solids (TSS) concentrations were almost identical between the two stations (0.47 and 0.42 mg l⁻¹, respectively). In addition, the attenuation and absorption coefficients showed that the CPAs in the water body were only inorganic suspended solids (ISS) more than 0.7 μm in diameter, and specific CPAs, such as dissolved mineral ions and aqueous colloids, were not observed in the lake. Simulation of the radiometric water color showed that the radiation around 600 nm of wavelength (yellow region) steeply increased with decreasing bottom depth, indicating that the water colors of Lake Onneto are strongly governed by the light reflection from yellowish bottom sediments.