But the range of differentiation of their concentrations far exceeds that normally recorded in the open waters of the Baltic and other seas. A very much more precise definition of how each of these groups of

substances modifies the reflectance spectra Rrs(λ) is possible from a study of these lake waters than of sea waters. The aim of the present work was therefore to define this influence, i.e. to interpret the shapes of the reflectance spectra Rrs(λ) and to establish correlations between the spectral reflectance band ratio and the chlorophyll a concentration, the SPM concentration CSPM, and the index of CDOM concentration in the water, i.e. the coefficient selleck screening library of light absorption aCDOM in the blue waveband (440 nm). For comparison the reflectance spectra of the Baltic Sea are also presented. The reflectance was calculated as the ratio of the water-leaving upward radiance Lu(0+, λ) and the downward irradiance Ed(0+, λ) just above the water surface: Rrs(λ) = Lu(0+, λ)/Ed(0+, λ). The downward

irradiance Ed(0+, λ) was measured above the water; the upward radiance in the water was measured every 10 cm depth from 0.1–2 m, extrapolated to the water surface Lu(0−, λ) and to the water-leaving radiance buy Dabrafenib as Lu(0+, λ) = 0.544 Lu(0−, λ) (see Mueller & Austin 1995, Darecki et al. 2005). The irradiance and radiance were measured with a Satlantic Hyper Spectral Radiometer HyperPro in 136 channels in the 350–800 nm spectral range. The absorption spectra aCDOM(λ) and the chlorophyll a concentrations Ca were estimated from spectrophotometric measurements using

a Hitachi U 2810 UV-VIS Spectrophotometer. Phytoplankton pigment concentrations were estimated using high performance liquid chromatography (HPLC). SPM concentrations (CSPM) were determined as the particulate dry mass collected on Whatman GF/F glass filters from known volumes of water. Optical measurements were carried out in situ and water samples were collected for analysis from boats adapted for such purposes, usually once a month, Hydroxychloroquine except when the lakes were covered with ice. The measurement stations were located over the deepest point in the main basin of each lake, as far distant as possible from sources that could accidentally alter the water’s properties, i.e. far from river mouths, canals joining the lake with the sea, etc. The results given below refer to the euphotic zones of the largest, representative parts of each of the investigated lakes. 235 sets of empirical data points obtained from the simultaneous measurement of the reflectance spectra Rrs(λ), chlorophyll concentrations Ca, suspended particulate matter concentrations CSPM and absorption spectra aCDOM(λ) were collected for the analysis and interpretation of the remote sensing reflectance spectra Rrs(λ).