Optical and biological properties of Lake Ülemiste, a water reservoir of the city of Tallinn I: Water transparency and optically active substances in the water
Optical and biological properties of Lake Ülemiste, a water reservoir of the city of Tallinn I: Water transparency and optically active substances in the water
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塔林市水库乌勒米斯特湖的光学和生物特性 I：水的透明度和水中的光学活性物质
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
M. Hussainov
中科院分区：
文献类型：
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作者：
A. Erm;H. Arst;T. Trei;A. Reinart;M. Hussainov
Optical and biological measurements were performed in Lake Ulemiste in the summer of 1997 (four measurement days), and from May to October in 1998 (12 measurement days). This kind of data, describing the type and amount of optically active substances in the water, phytoplankton characteristics, the underwater light field, and temperature–oxygen situation in the lake are necessary when estimating the ecological state of the lake. Lake Ulemiste is the main drinking water reservoir of Tallinn, the capital of Estonia. Phytoplankton abundance and biomass, chlorophyll a and suspended matter were determined from collected Lake Ulemiste water samples in the laboratory. Spectrophotometrical processing of the filtered and unfiltered water was carried out to describe the beam attenuation coefficient spectra and optical influence of yellow substance in the water. Vertical profiles of downwelling irradiance of the PAR (400–700 m) region of the spectrum (and from these data the averaged over depth diffuse attenuation coefficient) were determined. The relative transparency of the water was estimated by using a Secchi disk. Passive optical remote measurements were episodically made from aboard a boat. Results obtained confirmed that Lake Ulemiste is turbid (almost hypertrophic), comparable with most turbid lakes in Estonia (e.g. Lake Vortsjarv) and Finland (Lake Tuusulanjarvi). Its chlorophyll a content varied within the range 13–121 mg m–3, phytoplankton biomass 3–107 mg L–1, phytoplankton abundance 65 000–999 000 mL–1, suspended matter 8–34 mg L–1, effective concentration of the yellow substance 6–30 mg L–1, diffuse attenuation coefficient of light in the PAR region 1.0–3.3 m–1 and a Secchi disk depth of 0.5–1.75 m. The temporal variation of the spatial averages of these parameters during 1998 was analysed. Almost all characteristics showed an increase from May to midsummer with a maximum in late July or in August (correspondingly the Secchi depth values were minimal in late summer). The amount of yellow substance was an exception, which was nearly constant during the observation period. The maximum level of chlorophyll a content in July and August 1998 markedly exceeded that in 1997, despite the fact that the summer of 1997 was sunny, but the summer of 1998 was cold and rainy. The correlative relationships between the different parameters were investigated together with the respective data for other lakes. They show that the data of Lake Ulemiste supplemented the correlation graph in the region of turbid lakes, whereby in all cases the correlation coefficient increased following the addition of Lake Ulemiste data. The highest correlation coefficient was obtained when light attenuation coefficient values were correlated with a sum of weighted concentrations of chlorophyll a, yellow substance and suspended matter (multiple regression analysis).
