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  • 1
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    Freshwater Biological Association | Ambleside, UK
    In:  http://aquaticcommons.org/id/eprint/5259 | 1256 | 2011-09-29 15:09:27 | 5259 | Freshwater Biological Association
    Publication Date: 2021-07-09
    Description: In recent collaborative biological sampling exercises organised by the Nottingham Regional Laboratory of the Severn-Trent Water Authority, the effect of handnet sampling variation on the quality and usefulness of the data obtained has been questioned, especially when this data is transcribed into one or more of the commonly used biological methods of water quality assessment. This study investigates if this effect is constant at sites with similar typography but differing water quality states when the sampling method is standardized and carried out by a single operator. An argument is made for the use of a lowest common denominator approach to give a more consistent result and obviate the effect of sampling variation on these biological assessment methods.
    Description: Bilateral study of methods 2 - Pollution Report No.8
    Keywords: Biology ; Limnology ; Pollution ; Sampling ; Samplers ; Methodology ; Standardization ; Rivers ; Invertebrate larvae ; England ; Trent River
    Repository Name: AquaDocs
    Type: monograph
    Format: application/pdf
    Format: application/pdf
    Format: 19
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  • 2
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    Freshwater Biological Association | Ambleside, UK
    In:  http://aquaticcommons.org/id/eprint/5270 | 1256 | 2011-09-29 15:10:29 | 5270 | Freshwater Biological Association
    Publication Date: 2021-07-09
    Description: At the present time hydrobiological indicators are widely used for the control of surface water quality. Results of the applying of methods suggested at the 1st Soviet-American seminar (1975), development of improved methods and estimation of their usefulness for various conditions are presented in this report. Among the criteria permitting an estimation of the degree and character of changes in water quality and their connection with the functioning of river ecosystems in general, the biological tests of natural waters appears to be the most universal one and is being carried out in two main directions — ecological and physiological. This study summarises approaches in both directions.
    Keywords: Biology ; Limnology ; Pollution ; River water ; Rivers ; Water quality ; Water quality control ; Indicators
    Repository Name: AquaDocs
    Type: monograph
    Format: application/pdf
    Format: application/pdf
    Format: 6
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  • 3
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    Freshwater Biological Association | Ambleside, UK
    In:  http://aquaticcommons.org/id/eprint/5287 | 1256 | 2011-09-29 15:12:00 | 5287 | Freshwater Biological Association
    Publication Date: 2021-07-09
    Description: Restoration of water-bodies from eutrophication has proved to be extremely difficult. Mathematical models have been used extensively to provide guidance for management decisions. The aim of this paper is to elucidate important problems of using models for predicting environmental changes. First, the necessity for a proper uncertainty assessment of the model, upon calibration, has not been widely recognized. Predictions must not be a single time trajectory; they should be a band, expressing system uncertainty and natural variability. Availability of this information may alter the decision to be taken. Second, even with well-calibrated models, there is no guarantee they will give correct projections in situations where the model is used to predict the effects of measures designed to bring the system into an entirely different ”operating point”, as is typically the case in eutrophication abatement. The concept of educated speculation is introduced to partially overcome this difficulty. Lake Veluwe is used as a case to illustrate the point. Third, as questions become more detailed, such as ”what about expected algal composition”, there is a greater probability of running into fundamental problems that are associated with predicting the behaviour of complex non-linear systems. Some of these systems show extreme initial condition sensitivity and even, perhaps, chaotic behaviour, and are therefore fundamentally unpredictable.
    Keywords: Ecology ; Limnology ; Pollution ; Eutrophication ; Algal blooms ; Phytoplankton ; Freshwater lakes ; Models ; Growth ; Modelling ; Equations ; Bacteria ; Prediction ; Netherlands ; Veluwemeer Lake
    Repository Name: AquaDocs
    Type: book_section , FALSE
    Format: application/pdf
    Format: application/pdf
    Format: 44-58
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  • 4
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    Freshwater Biological Association | Ambleside, UK
    In:  http://aquaticcommons.org/id/eprint/5285 | 1256 | 2011-09-29 15:11:44 | 5285 | Freshwater Biological Association
    Publication Date: 2021-07-09
    Description: The ”Vollenweider model” is a sophisticated mathematical statement about the long-range behaviour of (mainly temperate) lakes and their ability to support phytoplankton chlorophyll. Misapplication of the model, against which Vollenweider himself warned, has led to many misconceptions about the dynamics of plankton in lakes and reservoirs and about how best to manage systems subject to eutrophication. This contribution intends to frame the most important issues in context of the phosphorus- loading and phosphorus-limitation concepts. Emphasis is placed on the need to distinguish rate-limitation from capacity-limitation, to understand which is more manageable and why, to discern the mechanisms of internal recycling and their importance, and to appreciate the respective roles of physical and biotic components in local control of algal dynamics. Some general approaches to the management of water quality in lakes and reservoirs to eutrophication are outlined.
    Keywords: Ecology ; Limnology ; Pollution ; Eutrophication ; Algal blooms ; Phytoplankton ; Models ; Phosphorus ; Ecosystem management ; Nutrients (mineral) ; Plant growth ; Growth regulators ; Freshwater lakes
    Repository Name: AquaDocs
    Type: book_section , FALSE
    Format: application/pdf
    Format: application/pdf
    Format: 4-29
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  • 5
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    Freshwater Biological Association | Ambleside, UK
    In:  http://aquaticcommons.org/id/eprint/5290 | 1256 | 2011-09-29 15:08:14 | 5290 | Freshwater Biological Association
    Publication Date: 2021-07-09
    Description: In the mesotrophic-eutrophic Saidenbach Reservoir in Saxony, the nanoplankton and cyanobacteria have increased at the expense of diatom dominance, due to a doubling of the external phosphorus load in the last 15 years. However, the phosphorus sedimentation flux is still very high (up to 80% of the input), corresponding to more than 2 g m2 d-1 in terms of dry weight. There is a strong correlation between the abundance of diatoms in the euphotic zone and their sedimentation flux (with a delay of about 2 weeks). Only about 25% of the deposited material could be clearly attributed to plankton biomass; the remainder resulted from flocculation and precipitation processes or directly from the inflow of clay minerals. The ash content of the deposited material was high (73%). Thus the sedimentation flux can be considered to operate as an internal water-treatment/oligotrophication process within the lake. The neighbouring Neunzehnhain Reservoir still has a very clear water with a transparency up to 18 m depth. Though the sediment was not much lower than Saidenbach sediment in total phosphorus and total numbers of bacteria, sulphide was always absent and the ratio of Fe 2+ to Fe 3+ was very low in the upper (0- 5 cm) layer. Thus the external and internal phosphorus loads do not attain the critical level necessary to induce a ”phosphorus - phytoplankton” feedback loop.
    Keywords: Ecology ; Limnology ; Pollution ; Eutrophication ; Freshwater lakes ; Water quality control ; Phosphorus ; Water reservoirs ; Phytoplankton ; Growth ; Sedimentation ; Sediment composition ; Germany
    Repository Name: AquaDocs
    Type: book_section , FALSE
    Format: application/pdf
    Format: application/pdf
    Format: 94-106
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  • 6
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    Freshwater Biological Association | Ambleside, UK
    In:  http://aquaticcommons.org/id/eprint/5295 | 1256 | 2011-09-29 15:07:49 | 5295 | Freshwater Biological Association
    Publication Date: 2021-07-09
    Description: In a small lake, intermittent destratification was installed after several other physico-chemical and physical in-lake therapy measures (phosphorus immobilization, permanent destratification) had been tested without great success. If an aerobic sediment-water interface can be maintained, intermittent destratification removes cyanobacteria and prevents optimal development of other members of the photoautotrophic plankton. During growing seasons, increasing abundances of small-bodied herbivores (Bosmina) and Daphnia may have accounted for relatively low phytoplankton biomass as well. Intermittent destratification is a very fast-working in-lake measure and seems to be applicable even in relatively shallow lakes (〈 15 m), in which permanent destratification seems to be risky.
    Keywords: Ecology ; Limnology ; Pollution ; Eutrophication ; Algal blooms ; Destratification ; Ecosystem management ; Water quality control ; Phosphorus ; Eutrophic lakes ; Inhibitors ; Phytoplankton ; Zooplankton ; Biomass ; Germany ; Fischkaltersee
    Repository Name: AquaDocs
    Type: book_section , FALSE
    Format: application/pdf
    Format: application/pdf
    Format: 163-184
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  • 7
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    Freshwater Biological Association | Ambleside, UK
    In:  http://aquaticcommons.org/id/eprint/5291 | 1256 | 2011-09-29 15:07:52 | 5291 | Freshwater Biological Association
    Publication Date: 2021-07-09
    Description: Natural calcite precipitation in lakes is a well-known control mechanism of eutrophication. In hard-water lakes, calcite deposits on the flat bottoms of shallow lakes and near the shores of deeper lakes resulted from biogenic decalcification during the millenia after the last glacial period. The objective of a new restoration technology is to intensify the natural process of precipitation by utilizing the different qualities of calcareous mud layers. In a pilot experiment in Lake Rudower See, East Germany, phosphorus-poor deeper layers of the sediments were flushed out and spread over the phosphorus-rich uppermost sediments, to promote the co- precipitation of calcite with phosphorus from the water-column.
    Keywords: Ecology ; Limnology ; Pollution ; Eutrophication ; Freshwater lakes ; Phosphorus ; Calcitization ; Algal blooms ; Calcite ; Sedimentation ; Germany
    Repository Name: AquaDocs
    Type: book_section , FALSE
    Format: application/pdf
    Format: application/pdf
    Format: 107-111
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  • 8
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    Freshwater Biological Association | Ambleside, UK
    In:  http://aquaticcommons.org/id/eprint/5301 | 1256 | 2011-09-29 15:07:11 | 5301 | Freshwater Biological Association
    Publication Date: 2021-07-09
    Description: The cyanobacteria that cause problems in water supply are principally the colonial forms that are buoyed up by gas vesicles. The success of these organisms is due, in part, to their gas vesicles, which enable them to perform vertical migrations or to maintain themselves in the euphotic zone. The gas vesicles are also the root cause of the problems. In calm periods they cause the cyanobacteria to float to the water surface forming noxious scums, and they may prevent the colonies from sedimenting in water treatment plants. Gas vesicles are hollow, gas-filled structures; they are rigid but can be collapsed by the application of pressure. Their critical collapse pressure is influenced by their dimensions, which vary in different organisms. Gas vesicles are formed by the assembly of two types of protein, which determine their mechanical and physical properties. Methods for collapsing gas vesicles in natural populations of cyanobacteria will be considered. They may have application to the control of cyanobacteria in water supply.
    Keywords: Ecology ; Limnology ; Pollution ; Eutrophication ; Algal blooms ; Gases ; Buoyancy ; Algae ; Bacteria ; Photosynthesis ; Growth ; Competition
    Repository Name: AquaDocs
    Type: book_section , FALSE
    Format: application/pdf
    Format: application/pdf
    Format: 150-162
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  • 9
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    Freshwater Biological Association | Ambleside, UK
    In:  http://aquaticcommons.org/id/eprint/5293 | 1256 | 2011-09-29 15:08:09 | 5293 | Freshwater Biological Association
    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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  • 10
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    Freshwater Biological Association | Ambleside, UK
    In:  http://aquaticcommons.org/id/eprint/5288 | 1256 | 2011-09-29 15:08:15 | 5288 | Freshwater Biological Association
    Publication Date: 2021-07-09
    Description: Biomanipulation is a form of biological engineering in which organisms are selectively removed or encouraged to alleviate the symptoms of eutrophication. Most examples involve fish and grazer zooplankton though mussels have also been used. The technique involves continuous management in many deeper lakes and is not a substitute for nutrient control. In some lakes, alterations to the lake environment have given longer-term positive effects. And in some shallow lakes, biomanipulation may be essential, alongside nutrient control, in re- establishing former aquatic-plant-dominated ecosystems which have been lost through severe eutrophication. The emergence of biomanipulation techniques emphasises that lake systems are not simply chemical reactors which respond simply to engineered chemical changes, but very complex and still very imperfectly understood ecosystems which require a yet profounder understanding before they can be restored with certainty.
    Keywords: Ecology ; Limnology ; Pollution ; Eutrophication ; Algal blooms ; Freshwater lakes ; Biomanipulation ; Water quality control
    Repository Name: AquaDocs
    Type: book_section , FALSE
    Format: application/pdf
    Format: application/pdf
    Format: 73-81
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