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  • 1
    Electronic Resource
    Electronic Resource
    The rise and fall of Asterionella formosa in the South Basin of Windermere: analysis of a 45-year series of data (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 31 (1994), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 〈list xml:id="l1" style="custom"〉1 The changes in abundance of Asterionella formosa in the South Basin of Windermere between 1946 and 1990 are described and analysed. The average seasonal cycle for the 45-year period shows an overwintering population of about 10 cell ml−1 which increases with an exponential rate of 0.09 loge day−1 to an annual maximum of 4000 cell ml−1 by about Day 124. There is then a rapid decline at an exponential rate of loss of 0.29 loge day−1 to values which typically are less than 0.01 cell ml−1 in mid-summer. By about Day 240 a second period of rapid increase occurs with an exponential rate of increase of 0.18 loge. day−1 to a plateau of about 7 cell ml−1 in late autumn and early winter.2 This average pattern is subject to considerable year-to-year variation. The timing and extent of the increase in the autumn was particularly variable. The rate of increase in the spring was strongly positively correlated, and that in the autumn strongly negatively correlated, with the day at which the exponential phase started. Rates for these two phases of increase were not statistically different when expressed in terms of time from mid-summer, which reinforces earlier conclusions that light availability is the main factor governing the rate of spring increase and suggests that this is also the case for the autumn increase.3 Eight descriptors of seasonal development showed statistically significant changes over the 45 years. Early winter populations declined from 27 to 4 cell ml−1, and linked to this the day at which cell concentrations exceeded 50 cell ml−1 occurred later by 24 days from Day 54 in 1946 to 78 in 1990. The lower early winter population appears to be linked to a lower end of year population as this decreased between 1946 and 1968 from 46 to 2 cell ml−1, and then increased slightly to 7 cell ml−1 in 1990. The start of the spring exponential increase occurred on Day 57 in 1946 and started earlier by 19 days in 1968 but then occurred later, at Day 76, in 1990. The duration of the spring increase got shorter by 23 days, from 67 days in 1946 to 44 days in 1990. The maximum rate of increase rose from 0.065 loge day−1 in 1946 to 0.112 loge day−1 in 1990. The annual maximum declined from 9863 cell ml−1 in 1946 to 2278 cell ml−1 in 1968 and then increased to 6159 cell ml−1 in 1990. The annual geometric mean decreased from 61 cell ml−1 in 1946 to 5 cell ml−1 in 1968 and remained nearly constant subsequently.4 In many cases, the precise underlying causes of these changes were not apparent. However, the increase with time of rate of increase in the spring appeared to be linked to a later start and hence growth under higher light. There was no significant cyclical change in any of the descriptors studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1994.tb00835.x
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  • 2
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    Changes of water quality and sediment phosphorus of a small productive lake following decreased phosphorus loading (2021)
    Freshwater Biological Association | Ambleside, UK
    In:  http://aquaticcommons.org/id/eprint/5293 | 1256 | 2011-09-29 15:08:09 | 5293 | Freshwater Biological Association
    Details
    Publication Date: 2021-07-09
    Description: Esthwaite Water is the most productive or eutrophic lake in the English Lake District. Since 1945 its water quality has been determined from weekly or biweekly measurements of temperature, oxygen, plant nutrients and phytoplankton abundance. The lake receives phosphorus from its largely lowland-pasture catchment, sewage effluent from the villages of Hawkshead and Near Sawrey, and from a cage-culture fish farm. From 1986 phosphorus has been removed from the sewage effluent of Hawkshead which was considered to contribute between 47% and 67% of the total phosphorus loading to the lake. At the commencement of phosphorus removal regular measurements of phosphorus in the superficial 0-4 cm layer of lake sediment were made from cores collected at random sites. Since 1986 the mean annual concentration of alkali-extractable sediment phosphorus has decreased by 23%. This change is not significant at the 5% level but nearly so. There has been no marked change in water quality over this period. Summer dominance of blue-green algae which arose in the early 1980s after decline of the previous summer forms, Ceratium spp., has been maintained. Improvement in water quality is unlikely to be achieved at the present phosphorus loading.
    Keywords: Chemistry ; Limnology ; Pollution ; Eutrophication ; Freshwater lakes ; Limnological surveys ; Phosphorus ; Phytoplankton ; Primary production ; Sediment analysis ; Water quality ; England ; Esthwaite Water
    Repository Name: AquaDocs
    Type: book_section , FALSE
    Format: application/pdf
    Format: application/pdf
    Format: 119-131
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