Steinhuder Meer is an extremely shallow lake (mean depth 1.35 m). The autochthonous sediments are... more Steinhuder Meer is an extremely shallow lake (mean depth 1.35 m). The autochthonous sediments are frequently suspended by waves and then drifted by currents ("Treibmudde"). It is usually only the upper few millimetres of the mud which are disturbed. The transportation of suspended matter by the outflow is calculated to be about 500 t dry wt. per year. Due to the phenomenon of "Treibmudde" there may be a heavy silting in the wind-sheltered parts of the lake, with up to 25 em per year being recorded in seston samplers. There is a rapid decomposition of nitrogen containing compounds in the "Treibmudde" being even detectable in the seston samplers. In contrast the mineralisation of phosphorus compounds is slower. Indirect evidence is presented for a vertical distribution of phosphorus and iron within the sediments with maxima of concentrations at the surface. The calcium contents of the "Treibmudde" and of the sediments are very low, although probably a biogenic precipitation of lime occurs during summer time.
Phytoplankton are the major primary producers in Lough Neagh (cf. Chapter 12) and during the 1970... more Phytoplankton are the major primary producers in Lough Neagh (cf. Chapter 12) and during the 1970s a series of studies were carried out to estimate the amount of energy fixed by them in photosynthesis. Most of the work was based on oxygen evolution (Jewson, 1975, 1976; Jewson and Wood, 1975; Jewson and Taylor, 1978; Jones, 1977b, 1978) but 14C-uptake (Jewson, 1977b; Dring and Jewson, 1982) and carbohydrate accumulation (Gibson, 1975, 1977) have also been measured. The majority of the material summarised in this chapter refers to the open lake but results are also included for a shallow area, Kinnego Bay (Jewson, 1976; Jones, 1977a,b,c).
A desktop incubator with temperature control over the range 1–20°C (±0.5°C) was designed to hold ... more A desktop incubator with temperature control over the range 1–20°C (±0.5°C) was designed to hold two microtitre plates. Illumination of individual wells in the plate was by a matrix of 96 light-emitting diodes, whose intensity, period and pulsation could be controlled individually in each of 12 rows of eight chambers. The incubator was used to test how the length of
A strong spectral variation in underwater light penetration is found in Lough Neagh, particularly... more A strong spectral variation in underwater light penetration is found in Lough Neagh, particularly in the wavelengths available for photosynthesis (400-700 nm). Using a spectroradiometer and coloured filters to analyse the underwater light climate, the depth of the euphotic zone was found to vary between 1 and 3 m and was largely attributable to changes in algal density between 26 and 92 mg chlorophyll a m-3 in the open lake and between 48 and 300 mg chl a m-3 in a shallow almost enclosed area, Kinnego Bay. Although self-shading of the algal cells is important at high crops the contribution from non-algal sources becomes increasingly significant at low crop concentrations. The factors controlling the algal content of the euphotic zone for the open lake (70-174 mg chl a M-2) and Kinnego Bay (114-380 mg chl a M-2) are discussed and compared with other well-mixed eutrophic lakes.
Auxospores of Aulacoseira herzogii (Lemmermann) Simonsen were found in Lake Banani (Dhaka, Bangla... more Auxospores of Aulacoseira herzogii (Lemmermann) Simonsen were found in Lake Banani (Dhaka, Bangladesh) during the monsoon season in September 1992. In the following weeks, the lake became overgrown by a floating canopy of water hyacinth (Eichhornia crassipes) and die cell concentration of A. herzogii declined. During auxosporulation, diameter regeneration of A. herzogii cells was approximately three times, from 4.9 μm (mean of parent cells) to 15.1 μm (mean of initial cells). In this species, some morphological features, such as number of separation spines (1–8) and rimoportulae (up to 8), are size dependent. Other aspects of population size-structure, reproduction and ecology of this rarely reported species are presented.
Steinhuder Meer is an extremely shallow lake (mean depth 1.35 m). The autochthonous sediments are... more Steinhuder Meer is an extremely shallow lake (mean depth 1.35 m). The autochthonous sediments are frequently suspended by waves and then drifted by currents ("Treibmudde"). It is usually only the upper few millimetres of the mud which are disturbed. The transportation of suspended matter by the outflow is calculated to be about 500 t dry wt. per year. Due to the phenomenon of "Treibmudde" there may be a heavy silting in the wind-sheltered parts of the lake, with up to 25 em per year being recorded in seston samplers. There is a rapid decomposition of nitrogen containing compounds in the "Treibmudde" being even detectable in the seston samplers. In contrast the mineralisation of phosphorus compounds is slower. Indirect evidence is presented for a vertical distribution of phosphorus and iron within the sediments with maxima of concentrations at the surface. The calcium contents of the "Treibmudde" and of the sediments are very low, although probably a biogenic precipitation of lime occurs during summer time.
There have been many anecdotal references to the colour and turbidity of Lough Neagh since it was... more There have been many anecdotal references to the colour and turbidity of Lough Neagh since it was reported as turning to blood in AD683 (Annals of Ulster and other references cited by Marshall, 1934). However, quantitiative measurements of underwater light penetration are unknown before 1968. Since this time a range of methods of investigation have been used including Secchi disc (Gibson, 1975), broad-band filters and spectroradiometric data (Jewson, 1977; Jewson and Taylor, 1978).
The availability of light in Lough Neagh restricts the growth of most benthic (bottom living) pla... more The availability of light in Lough Neagh restricts the growth of most benthic (bottom living) plants to a narrow coastal strip where the water depth does not exceed 3 m (Fig. 12.1). This represents an area of approximately 50 km2, which is about 13% of the surface area of the lake. This inshore zone consists mainly of rocks and stones (Briggs, 1984) but there are also long stretches of sandy beaches. Both of these are erosive environments subject to considerable wave action, so fine sediments do not accumulate but are resuspended and transported out into deeper water. Rooted vegetation does not grow well in these conditions and is limited to a few sheltered areas. The major primary producers are microbial cells living on the surface of rocks and stones (epilithic) or attached to sand grains (epipsammic).
Steinhuder Meer is an extremely shallow lake (mean depth 1.35 m). The autochthonous sediments are... more Steinhuder Meer is an extremely shallow lake (mean depth 1.35 m). The autochthonous sediments are frequently suspended by waves and then drifted by currents ("Treibmudde"). It is usually only the upper few millimetres of the mud which are disturbed. The transportation of suspended matter by the outflow is calculated to be about 500 t dry wt. per year. Due to the phenomenon of "Treibmudde" there may be a heavy silting in the wind-sheltered parts of the lake, with up to 25 em per year being recorded in seston samplers. There is a rapid decomposition of nitrogen containing compounds in the "Treibmudde" being even detectable in the seston samplers. In contrast the mineralisation of phosphorus compounds is slower. Indirect evidence is presented for a vertical distribution of phosphorus and iron within the sediments with maxima of concentrations at the surface. The calcium contents of the "Treibmudde" and of the sediments are very low, although probably a biogenic precipitation of lime occurs during summer time.
Phytoplankton are the major primary producers in Lough Neagh (cf. Chapter 12) and during the 1970... more Phytoplankton are the major primary producers in Lough Neagh (cf. Chapter 12) and during the 1970s a series of studies were carried out to estimate the amount of energy fixed by them in photosynthesis. Most of the work was based on oxygen evolution (Jewson, 1975, 1976; Jewson and Wood, 1975; Jewson and Taylor, 1978; Jones, 1977b, 1978) but 14C-uptake (Jewson, 1977b; Dring and Jewson, 1982) and carbohydrate accumulation (Gibson, 1975, 1977) have also been measured. The majority of the material summarised in this chapter refers to the open lake but results are also included for a shallow area, Kinnego Bay (Jewson, 1976; Jones, 1977a,b,c).
A desktop incubator with temperature control over the range 1–20°C (±0.5°C) was designed to hold ... more A desktop incubator with temperature control over the range 1–20°C (±0.5°C) was designed to hold two microtitre plates. Illumination of individual wells in the plate was by a matrix of 96 light-emitting diodes, whose intensity, period and pulsation could be controlled individually in each of 12 rows of eight chambers. The incubator was used to test how the length of
A strong spectral variation in underwater light penetration is found in Lough Neagh, particularly... more A strong spectral variation in underwater light penetration is found in Lough Neagh, particularly in the wavelengths available for photosynthesis (400-700 nm). Using a spectroradiometer and coloured filters to analyse the underwater light climate, the depth of the euphotic zone was found to vary between 1 and 3 m and was largely attributable to changes in algal density between 26 and 92 mg chlorophyll a m-3 in the open lake and between 48 and 300 mg chl a m-3 in a shallow almost enclosed area, Kinnego Bay. Although self-shading of the algal cells is important at high crops the contribution from non-algal sources becomes increasingly significant at low crop concentrations. The factors controlling the algal content of the euphotic zone for the open lake (70-174 mg chl a M-2) and Kinnego Bay (114-380 mg chl a M-2) are discussed and compared with other well-mixed eutrophic lakes.
Auxospores of Aulacoseira herzogii (Lemmermann) Simonsen were found in Lake Banani (Dhaka, Bangla... more Auxospores of Aulacoseira herzogii (Lemmermann) Simonsen were found in Lake Banani (Dhaka, Bangladesh) during the monsoon season in September 1992. In the following weeks, the lake became overgrown by a floating canopy of water hyacinth (Eichhornia crassipes) and die cell concentration of A. herzogii declined. During auxosporulation, diameter regeneration of A. herzogii cells was approximately three times, from 4.9 μm (mean of parent cells) to 15.1 μm (mean of initial cells). In this species, some morphological features, such as number of separation spines (1–8) and rimoportulae (up to 8), are size dependent. Other aspects of population size-structure, reproduction and ecology of this rarely reported species are presented.
Steinhuder Meer is an extremely shallow lake (mean depth 1.35 m). The autochthonous sediments are... more Steinhuder Meer is an extremely shallow lake (mean depth 1.35 m). The autochthonous sediments are frequently suspended by waves and then drifted by currents ("Treibmudde"). It is usually only the upper few millimetres of the mud which are disturbed. The transportation of suspended matter by the outflow is calculated to be about 500 t dry wt. per year. Due to the phenomenon of "Treibmudde" there may be a heavy silting in the wind-sheltered parts of the lake, with up to 25 em per year being recorded in seston samplers. There is a rapid decomposition of nitrogen containing compounds in the "Treibmudde" being even detectable in the seston samplers. In contrast the mineralisation of phosphorus compounds is slower. Indirect evidence is presented for a vertical distribution of phosphorus and iron within the sediments with maxima of concentrations at the surface. The calcium contents of the "Treibmudde" and of the sediments are very low, although probably a biogenic precipitation of lime occurs during summer time.
There have been many anecdotal references to the colour and turbidity of Lough Neagh since it was... more There have been many anecdotal references to the colour and turbidity of Lough Neagh since it was reported as turning to blood in AD683 (Annals of Ulster and other references cited by Marshall, 1934). However, quantitiative measurements of underwater light penetration are unknown before 1968. Since this time a range of methods of investigation have been used including Secchi disc (Gibson, 1975), broad-band filters and spectroradiometric data (Jewson, 1977; Jewson and Taylor, 1978).
The availability of light in Lough Neagh restricts the growth of most benthic (bottom living) pla... more The availability of light in Lough Neagh restricts the growth of most benthic (bottom living) plants to a narrow coastal strip where the water depth does not exceed 3 m (Fig. 12.1). This represents an area of approximately 50 km2, which is about 13% of the surface area of the lake. This inshore zone consists mainly of rocks and stones (Briggs, 1984) but there are also long stretches of sandy beaches. Both of these are erosive environments subject to considerable wave action, so fine sediments do not accumulate but are resuspended and transported out into deeper water. Rooted vegetation does not grow well in these conditions and is limited to a few sheltered areas. The major primary producers are microbial cells living on the surface of rocks and stones (epilithic) or attached to sand grains (epipsammic).
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