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  • 1
    ISSN: 1573-5117
    Keywords: P-loading ; P concentration ; sewage water treatment plant ; agricultural fertilization control program ; fish reduction ; Secchi depth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Monitoring Lake Ringsjön's water chemistry, i.e. of pH, PO4-phosphorus, total phosphorus, Kjeldahl nitrogen, NO4+NO3-nitrogen, total nitrogen, chlorophyll a concentration and Secchi depth, has been conducted on a relatively continuous basis since the mid 1960s. Here, I analyze this data by graphical methods and discriminant analysis. The results show that there was a pronounced decrease in Secchi depth and an increase in phosphorus and chlorophyll a concentrations during the late 1960s and early 1970s. To improve conditions in the lake, new sewage water treatment techniques, using chemical precipitation techniques with post-filtration, were put into operation in the late 1970s in Hörby and Höör. A few years later, new recommendations were given to the farmers about use of fertilizers to further decrease the nutrient load to Lake Ringsjön. The concentrations of phosphorus and chlorophyll a started to decrease in the early 1980s, but there was no increase in Secchi depth. From 1989 to 1991, Secchi depth increased in the three basins of Lake Ringsjön. This increase in Secchi depth co-occurred in time with: (a) a fish-kill in Eastern Basin (1988), fish reductions in Sätofta Basin (1990) and Western Basin (1992); (b) a very low phosphorus loading in 1989 (4.7 tons); and (c) phosphorus concentrations in the lake water below 100 μg l−1.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 404 (1999), S. 65-75 
    ISSN: 1573-5117
    Keywords: fish community ; fish reduction ; biomanipulation ; piscivores ; planktivores
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lake Ringsjön in southern Sweden was restored by biomanipulation by means of a reduction in zooplanktivorous cyprinids. The fish community in the three different Basins of Lake Ringsjön were followed between 1987 and 1994. In 1990, c. 100 tons (60% of the community) were removed from Sätofta Basin, in 1988, c. 500 tons (80%) were removed from Eastern Basin and in 1992, c. 120 tons (50%) of cyprinids were removed from Western Basin. In all basins, the fish biomass was much lower after fish reduction than before, but only in Eastern Basin has the proportion of piscivores increased substantially (from 10% to 25–40%). Due to very high abundance of young-of-the-year following the fish reductions, the fish abundance has increased in all basins. The abundance of the young-of-the-year was negatively correlated to the abundance of piscivore perch at the 3 m depth. Although the young-of-the-year abundance was very high after the fish reduction, there are no clear evidences that this affects recruitment to the adult populations. The results are discussed in relation to critical fish biomasses and critical proportions of planktivory and piscivory to ensure a long lasting effect of fish reduction.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5117
    Keywords: P-loading ; P concentration ; sewage water treatment plant ; agricultural fertilization control program ; fish reduction ; Secchi depth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Monitoring Lake Ringsjön's water chemistry, i.e. of pH, PO4-phosphorus, total phosphorus, Kjeldahl nitrogen, NO4+NO3-nitrogen, total nitrogen, chlorophyll a concentration and Secchi depth, has been conducted on a relatively continuous basis since the mid 1960s. Here, I analyze this data by graphical methods and discriminant analysis. The results show that there was a pronounced decrease in Secchi depth and an increase in phosphorus and chlorophyll a concentrations during the late 1960s and early 1970s. To improve conditions in the lake, new sewage water treatment techniques, using chemical precipitation techniques with post-filtration, were put into operation in the late 1970s in Hörby and Höör. A few years later, new recommendations were given to the farmers about use of fertilizers to further decrease the nutrient load to Lake Ringsjön. The concentrations of phosphorus and chlorophyll a started to decrease in the early 1980s, but there was no increase in Secchi depth. From 1989 to 1991, Secchi depth increased in the three basins of Lake Ringsjön. This increase in Secchi depth co-occurred in time with: (a) a fish-kill in Eastern Basin (1988), fish reductions in Sätofta Basin (1990) and Western Basin (1992); (b) a very low phosphorus loading in 1989 (4.7 tons); and (c) phosphorus concentrations in the lake water below 100 μg l−1.
    Type of Medium: Electronic Resource
    Signatur Availability
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  • 4
    ISSN: 1573-5117
    Keywords: benthic macroinvertebrates ; fish reduction ; biomanipulation ; bioturbation ; nutrient retention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The benthic macroinvertebrate community in a severely eutrophicated South Swedish lake, Lake Ringsjön, was found to re-establish after the lake was subjected to a substantial reduction of cyprinids (mainly bream and roach). Being totally dominated by chironomids and oligochaetes during the 1980s, the lake became repopulated by groups like Amphipoda, Ephemeroptera, Coleoptera and Mollusca after the fish reduction in 1988–1992. These groups appeared in numbers similar to that found in 1969, before the lake entered its worst stage of eutrophication. The re-establishment of the invertebrates mainly occurred in the littoral parts of the lake. The profundal community was still dominated by chironomids and oligochaetes after the fish reduction. The increase in numbers of benthic macroinvertebrates in the littoral zone of the lake was likely an effect of lowered predation pressure from fish. The potential role of an increased macroinvertebrate abundance due to fish removal and its effects on recirculation of nutrients over the sediment–water interface is discussed. It was observed that average total nitrogen retention in Lake Ringsjön before and after the reduction was 59±5% and 82±15%, respectively.
    Type of Medium: Electronic Resource
    Signatur Availability
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 404 (1999), S. 65-75 
    ISSN: 1573-5117
    Keywords: fish community ; fish reduction ; biomanipulation ; piscivores ; planktivores
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lake Ringsjön in southern Sweden was restored by biomanipulation by means of a reduction in zooplanktivorous cyprinids. The fish community in the three different Basins of Lake Ringsjön were followed between 1987 and 1994. In 1990, c. 100 tons (60% of the community) were removed from Sätofta Basin, in 1988, c. 500 tons (80%) were removed from Eastern Basin and in 1992, c. 120 tons (50%) of cyprinids were removed from Western Basin. In all basins, the fish biomass was much lower after fish reduction than before, but only in Eastern Basin has the proportion of piscivores increased substantially (from 10% to 25–40%). Due to very high abundance of young-of-the-year following the fish reductions, the fish abundance has increased in all basins. The abundance of the young-of-the-year was negatively correlated to the abundance of piscivore perch at the 3 m depth. Although the young-of-the-year abundance was very high after the fish reduction, there are no clear evidences that this affects recruitment to the adult populations. The results are discussed in relation to critical fish biomasses and critical proportions of planktivory and piscivory to ensure a long lasting effect of fish reduction.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1573-5117
    Keywords: benthic macroinvertebrates ; fish reduction ; biomanipulation ; bioturbation ; nutrient retention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The benthic macroinvertebrate community in a severely eutrophicated South Swedish lake, Lake Ringsjön, was found to re-establish after the lake was subjected to a substantial reduction of cyprinids (mainly bream and roach). Being totally dominated by chironomids and oligochaetes during the 1980s, the lake became repopulated by groups like Amphipoda, Ephemeroptera, Coleoptera and Mollusca after the fish reduction in 1988–1992. These groups appeared in numbers similar to that found in 1969, before the lake entered its worst stage of eutrophication. The re-establishment of the invertebrates mainly occurred in the littoral parts of the lake. The profundal community was still dominated by chironomids and oligochaetes after the fish reduction. The increase in numbers of benthic macroinvertebrates in the littoral zone of the lake was likely an effect of lowered predation pressure from fish. The potential role of an increased macroinvertebrate abundance due to fish removal and its effects on recirculation of nutrients over the sediment–water interface is discussed. It was observed that average total nitrogen retention in Lake Ringsjön before and after the reduction was 59±5% and 82±15%, respectively.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
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