A simple and inexpensive 4π light collector and two designs for a light meter for light attenuation studies

Williams, Peter J.; Jenkinson, N. W.

doi:10.1111/j.1365-2427.1980.tb01223.x

Cited by 6 publications

(3 citation statements)

References 7 publications

(1 reference statement)

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“…We continued the time-series until the year of 2000. The vertical light attenuation coefficient (K d ) was measured in 1995 and 1996 using an underwater 4-π PhAR collector (Williams and Jenkinson, 1980). Between 1992-2000, K d was calculated by fitting the principle model for shallow lakes given by Scheffer (1998), K d = a + b Chl + c/S, to the measured data of K d , chlorophyll a concentrations (Chl), and Secchi depth (S).…”

Section: Methodsmentioning

confidence: 99%

Climate-related changes of phytoplankton seasonality in large shallow Lake Võrtsjärv, Estonia

Nõges

Laas

2010

Aquatic Ecosystem Health &Amp; Management

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Water level changes (7-year moving averages) in Lake Võrtsjärv (Estonia) during 1885-2000 were correlated with winter patterns in the North Atlantic Oscillation (NAO) index. In this shallow lake (270 km 2 , mean depth 2.8 m), where the annual water level amplitude is 1.4 m and the absolute range is 3.2 m, hydrology is the main driving force for the ecosystem. Control of phytoplankton growth was mediated by ice conditions in spring, and by water level in summer and autumn. Winter air temperature similarly influenced the biomass of cyanobacteria and diatoms in spring; while the effect of the ice-cover duration was more pronounced on cyanobacteria. Mean depth of the lake did not affect the phytoplankton biomass in spring, but clearly controlled it in summer and autumn. The direct impact of winter conditions on biological processes was restricted to a short post-winter period, but extended indirectly as the water level for the entire growing season depended strongly on the height of the spring flood peak.

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Section: Methodsmentioning

confidence: 99%

Climate-related changes of phytoplankton seasonality in large shallow Lake Võrtsjärv, Estonia

Nõges

Laas

2010

Aquatic Ecosystem Health &Amp; Management

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“…In situ expositions on 6 August 1997 at 8-10, 12-14, 16-18, on 2 August 2001 at 12-14 and 16-18, and on 3 August 2001 at 12-14 were carried out as described above. At the beginning of each exposition vertical water samples for pigment analysis were taken, and vertical distribution of light (W m )2 ) was measured using an underwater 4-p PhAR collector (Williams & Jenkinson, 1980). The vertical light attenuation coefficient (K d ) was calculated according to Lambert-BeerÕs law:…”

Section: Methodsmentioning

confidence: 99%

Primary Production of Phytoplankton in a Strongly Stratified Temperate Lake

Nõges

Kangro

2005

Hydrobiologia

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Lake Verevi (12.6 ha, maximum depth 11.0 m, mean depth 3.6 m) is a strongly eutrophic and stratified lake. Planktothrix agardhii is the most characteristic phytoplankton species in summer and autumn, while photosynthesizing sulphur bacteria can occur massively in the metalimnion. Primary production (PP) and chlorophyll a concentration (Chl a) were seasonally studied in 1991, 1993, 2000, and 2001. Vertical distribution of PP was rather complex, having usually two peaks, one at or near the surface (0-1 m), and another deeper (at 3-7 m) in the metalimnion. The values of dark fixation of CO 2 in the metalimnion were in most cases higher than those in the upper water layer. Considering the average daily PP 896 mg C m )2 and yearly PP 162 mg C m )2 , Secchi depth 2.34 m, and epilimnetic concentrations of chlorophyll a (19.6 mg m )3 ), total nitrogen and total phosphorus (TP, 52 mg m )3 ) in 2000, L. Verevi is a eutrophic lake of a 'goodÕ status. Considering the total amounts of nutrients stored in the hypolimnion, the average potential concentrations in the whole water column could achieve 1885 mg m )3 of TN and 170 mg m )3 of TP reflecting hypertrophic conditions and a 'badÕ status. Improvement of the epilimnetic water quality from the 1990s to the 2000s may have resulted from incomplete spring mixing and might not reflect the real improvement. A decreased nutrient concentration in the epilimnion has supported the establishment of a 'clear epilimnion stateÕ allowing light to penetrate into the nutrient-rich metalimnion and sustaining a high production of cyanobacteria and phototrophic sulphur bacteria.

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“…Routine sampling was performed once a month, in some periods more frequently, 2-4 times per month. Underwater light measurements with a 4-r PhAR collector (Williams & Jenkinson, 1980) were made in 1989 and 1995. Bottom irradiance (/g) was calculated according to Lambert-Beer's law:…”

Section: Methodsmentioning

confidence: 99%

The Effect of Fluctuating Water Level on the Ecosystem of Lake Võrtsjärv, Central Estonia

Nõges¹,

Nõges²

1998

Proceedings of the Estonian Academy of Sciences. Biology. Ecolo

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Lake Vortsjirv (270 km?) in Central Estonia is the second largest lake in the Baltic countries. It is a shallow and turbid eutrophic lake with a mean depth of 2.7 m and maximum depth of 6 m. The amplitude of water level (WL) fluctuations is large: the annual mean is 1.38 m, annual maximum 2.20 m, and the absolute range 3.20 m. Besides seasonal fluctuations, the annual mean WL of dry and rainy years differs by more than one metre. Long-term WL measurements (starting from 1885, daily measurements from November 1921) show a periodic alternation of low and high water states within about 30-year periods. Due to the shallowness of the lake, low-level periods are accompanied by several unfavourable phenomena like cyanophyte blooms, overgrowing by macrophytes, restricted spawning area for pike, and winter fish kills. Despite a higher external nutrient load in precipitation rich years, the rising WL has a positive effect on the ecological state of the lake. A decrease in phytoplankton and bacterioplankton biomass and in suspended solids concentration, resembling the effect of a reduction of the trophic status, is related to the strengthening of the light limitation effect on phytoplankton and a decline in sediment resuspension.Key words: water level, shallow lake, light limitation, Secchi depth, phytoplankton biomass, bacterioplankton, long-term investigations, sediment resuspension, water level regulation. 1972), resulted in a realistic regulation scheme. Considering the large drainage area, poor outflow conditions, and flat shores, Vortsjéarv represents a complicated

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A simple and inexpensive 4π light collector and two designs for a light meter for light attenuation studies

Cited by 6 publications

References 7 publications

Climate-related changes of phytoplankton seasonality in large shallow Lake Võrtsjärv, Estonia

Climate-related changes of phytoplankton seasonality in large shallow Lake Võrtsjärv, Estonia

Primary Production of Phytoplankton in a Strongly Stratified Temperate Lake

The Effect of Fluctuating Water Level on the Ecosystem of Lake Võrtsjärv, Central Estonia

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