Comparative reflectance properties of algal cultures with manipulated densities |
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Authors: | Anatoly A Gitelson John F Schalles Donald C Rundquist Frank R Schiebe Yosef Z Yacobi |
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Institution: | (1) Department of Energy and Environmental Physics, J. Blaustein Institute for Desert Research and Department of Geological and Environmental Sciences, Ben-Gurion University of the Negev, Sede Boker, 84990, Israel;(2) Department of Biology, Creighton University, Omaha, NE 68178-0103, USA;(3) Center for Advanced Land Management Information Technologies, School of Natural Resource Sciences, University of Nebraska-Lincoln, Lincoln, NE 68588-0517, USA;(4) SST Development Group, Inc., Stillwater, OK 74075-0918, USA;(5) Israel Oceanographic and Limnological Research, Kinneret Limnological Laboratory, P.O. Box 345, Tiberias, 1402, Israel |
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Abstract: | A comparative study was conducted with representatives of four ecologically important freshwater algal phyla (Chlorophyta,
Cyanophyta, Bacillariophyta and Pyrrophyta) in order to (1) analyze the relationship between reflectance spectral features
and algal density, and (2) to elucidate and characterize possible diagnostic spectral reflectance features for identification
of dominant groups in algal bloom states. Algae (two chlorophytes, a cyanophyte and a bacillariophyte) were cultured in mesocosm
tanks and then their densities were reduced through dilution with clear water in four experiments. In a fifth experiment,
use was made of the pyrrophyte Peridinium gatunense, which bloomed in Lake Kinneret, Israel, practically forming a unialgal
‘culture’. The basic quantitative procedures for spectroradiometeric measurements and support data collection (pigment concentrations)
were consistent among the experiments. Several spectral reflectance characteristics were found to be common to all the species
examined in the study: a depression between 440 and 500 nm, a salient trough around 670 nm, and prominent peaks centered around
570 nm and 700 nm. The increase in magnitude of a near infra-red peak and shift of its position towards longer wavelengths
with increased chlorophyll- a concentration was found to be a common trait for all the species studied. Other specific spectral
reflectance features were also found and are discussed here. Quantitatively different relationships of magnitude and position
of spectral reflectance features with chlorophyll- a concentration reflect different optical properties of algae (their scattering
and absorption). This may be useful for taxonomic characterization by remote sensing.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | algae absorption pigments reflectance spectral features |
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