Abstract

The magnitude and frequency of events leading to changes in turbidity have been studied in a large (61 km(2)), shallow (mean depth 3.4 m) wind-exposed lake basin at the western end of Lake Malaren, Sweden. In this paper we couple changes in suspended particulate inorganic material (SPIM) resulting from wind driven sediment resuspension, and variations in the discharge and sediment load, to spectral variations in subsurface light and estimates of photosynthetically active radiation (PAR). To accomplish this we use a semi-analytical model which predicts the spectral variations in downwelling irradiance (E-d(lambda)) and the attenuation coefficient of downwelling irradiance (K-d(lambda)), as a function of the concentrations of chlorophyll, dissolved yellow substances, and suspended inorganic and organic particulate material. Unusually high river discharge, led to large inputs of yellow substances and large in lake yellow substance concentrations (a(ys)(420)approximate to20 m(-1)), causing variations in yellow substance concentration to have the greatest role in influencing temporal trends in the attenuation of PAR and variations in the depth of the euphotic zone (Z(eup)). In spite of this, variations in SPIM could account for approximately 60% of the variation in Z(eup) attributed to changes in yellow substances alone. Our results show that changes in suspended sediment concentration leads to both long-term and short-term changes in the attenuation of PAR, even in the presence of high concentrations of dissolved yellow substances.

Keywords

PAR; attenuation; suspended sediment; particulate material; SPIM; SPM; yellow substance; CDOM

Published in

Hydrobiologia
2003, Volume: 494, number: 1-3, pages: 299-304
Publisher: KLUWER ACADEMIC PUBL

UKÄ Subject classification

Oceanography, Hydrology, Water Resources


Publication identifier

DOI: https://doi.org/10.1023/A:1025455424972

Permanent link to this page (URI)

https://res.slu.se/id/publ/102709