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Spectral distribution characteristics in downwelling irradiance and optical properties within the euphotic layer in the north basin of lake biwa japan

Tsuda, R.; Nakanishi, M.

Archiv fur Hydrobiologie 119(3): 279-292

1990


ISSN/ISBN: 0003-9136
Accession: 007811085

Measurements of downwelling spectral irradiance at various depths were performed during one year (May 1983-May 1984) at the fixed station in the north basin of Lake Biwa. The patterns of spectral distribution could be classified into three types, which were related to the chlorophyll-a (chl-a) concentration within the euphotic layer. The classification in each type was also examined from the spectral values of the diffuse attenuation coefficient Kd (.lambda.) m-1. The shape of the spectral Kd (.lambda.) curve depends not only on chl-a concentration within the euphotic layer but also on the algal species dominating. Euphotic depth Z(1%) could be determined as a function of light attenuation coefficients, and the relationship between chl-a amounts within the euphotic layer and the euphotic depth was linear in the presence of a high chl-a amounts exceeding about 50 mg m-2. The relationship between the light attenuation coefficient and the averaged chl-a concentration within the euphotic layer was also discussed from the aspects of the optical properties in the water.

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