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  • 1
    ISSN: 1573-0417
    Schlagwort(e): climatic change ; environmental reconstruction ; Kråkenes ; late-glacial ; multi-disciplinary project
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Kråkenes is the site of a small lake on the west coast of Norway that contains a long sequence of late-glacial sediments. The Younger Dryas is well represented, as a cirque glacier developed in the catchment at this time. This site offers unique opportunities to reconstruct late-glacial environments from independent sources of evidence; physical evidence (glacial geomorphology, sedimentology, palaeomagnetism, radiocarbon dating), and biological evidence from the remains of animals and plants derived from both the terrestrial and aquatic ecosystems. This report describes the background to the site, and the international multidisciplinary project to reconstruct late-glacial and early Holocene environmental and climatic changes at Kråkenes.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1573-5117
    Schlagwort(e): diatoms ; water quality ; acidification ; pH calibration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Although the ecological effects of surface wateracidification are now well researched, factorscontrolling the abundance and occurrence of aquaticorganisms in unpolluted acid-sensitive systems arepoorly known. The Høylandet region in central Norwayexperiences relatively low levels of atmosphericpollution and its surface waters, although acid, arenot significantly acidified. Hence lakes and streamsin this region were selected to study the influence ofwater chemistry on diatom algae. Relationships betweenthe two were explored using the multivariate techniqueof canonical correspondence analysis (CCA). Theprincipal water chemistry variables influencingspecies composition of periphytic diatoms were foundto be pH and water colour. Furthermore, therelationship between species abundance and pH wassufficiently strong to enable reconstruction of wateracidity from diatom data. Establishing the nature ofaquatic communities in atmospherically clean butgeologically sensitive regions is an important meansof identifying control systems against which therecovery of acidified lakes in polluted regions can beassessed. The Høylandet region has the potential toprovide a Europe-wide control system of this naturebut much further work is required to follow up andextend the results of this preliminary study.
    Materialart: Digitale Medien
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  • 3
    ISSN: 1573-5117
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Restoration goals for damaged freshwater habitats can bedefinedaccording to ecological as well as to chemical criteria. Fordisturbed lakes, the sediment microfossil record can be usedtoselect potential modern analogue sites as possible restorationtarget ecosystems.Fossil diatom assemblages in two acidified lakes (Round LochofGlenhead and Loch Dee) in Galloway, Scotland, were comparedfloristically with modern surface sediment samples from ca. 200lakes in Britain, Ireland, Sweden and Norway using numericaltechniques. Mean squared Chi-squared dissimilarity (SCD)valuesbased on between sample Chi-square distance measures were usedtocompare samples.‘Space-for-time substitution’ using diatom assemblage matchingtechniques identified several modern analogue sites withHebrideanLoch Teanga and Irish Lough Claggan possessing modern diatomflorasmost similar to those which existed at the Round Loch ofGlenheadand Loch Dee before acidification.From the point of view of atmospheric pollution, the mostcloselymatching modern analogue sites were not necessarily in themostpristine regions. Some analogues occurred in UK regions ofmoderateor low acid deposition and modern diatom assemblages inatmospherically cleaner mid Norway were generally less similarfloristically.It is argued that identification of modern analogue sitesraisesthe possibility of using time-space substitution of closelymatchedmodern and fossil samples to infer whole lake ecosystems.Diatoms are however poor indicators of some water chemistryvariables and the two closest matched modern analogue siteshavetoo high calcium concentrations making faunistic comparisonsquestionable.Identification of good modern analogue lakes can be improvedbyusing selection criteria, other than diatoms, to pre-selectsites.Screening inappropriate sites according to water chemistry andbasin features combined with a larger biological database ofmodernand fossil samples offers a promising way of refining theselectionprocesses.Despite necessary refinements, modern analogue matching canpotentially identify whole lake ecosystems that can serve asbiological target communities for currently disturbed sites.Beingbased on biological rather than chemical criteria, thisapproachdoes not rely on species-water chemistry transfer functions.It istherefore directly relevant to lake conservation andrestorationobjectives and offers an alternative method for reconstructing lakepalaeo-environments.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Water, air & soil pollution 85 (1995), S. 2467-2472 
    ISSN: 1573-2932
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract Critical loads maps for UK freshwaters have been produced on a 10×10 km grid square basis, and used to map critical load exceedances under various deposition scenarios. A single lake or stream site was selected to represent the most sensitive water body in each grid square using predefined criteria. In the UK a major programme of data screening and validation has been undertaken in order to address issues of accuracy and validity. A major part of this validation exercise, the within-square variability study, is designed to test the extent to which the site chosen for mapping represents the most sensitive water body within each grid square or mapping unit. Sampling of all lake sites in thirty-two randomly chosen 10 × 10 km grid squares has shown that in two thirds of cases, the selection exercise has identified a site in the lowest critical load class within a square. However, up to a third of all sites selected to represent grid squares could be replaced by more sensitive sites with a critical load smaller by at least one Skokloster class. The mean overestimate of “diatom model” critical loads for sulphur in the within-square variability study is 0.188 keq ha−1 yr−1. This means that current critical load maps show overestimates for some grid squares. In order to determine where the most sensitive site has not been identified, further work on catchment scale classification of freshwater sensitivity is being carried out.
    Materialart: Digitale Medien
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  • 5
    ISSN: 1573-2932
    Schlagwort(e): pigments ; diatoms ; cladocera ; ostracods ; chironomids ; chrysophytes ; sediments ; Late Pleistocene ; Holocene ; crater lake ; Italy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract This paper reports the results of biological analyses (pigments, diatoms, chrysophyte cysts, cladocerans, chironomids and ostracods) of a ca. 14 m-long sediment core recovered from Lake Albano (Central Italy) in the course of the EU-funded project PALICLAS (PALaeoenvironmental analysis of Italian Crater Lake and Adriatic Sediments). A reconstruction of the environmental evolution and ecosystem response of Lake Albano during the last ca. 30 kyr was possible. Additional information on lake level oscillation is obtained from benthic and planktonic palaeocommunities. Several oscillations in the productivity and the level of the lake were detected in the oldest sediment layers (from ca. 30 kyr BP to ca. 17 kyr BP), followed by a long (ca. 5 kyr BP) period of low productivity in which cold, holomictic conditions prevailed. A period of high biological activity and, probably, meromictic conditions during the early-mid Holocene was detected. A clear impact of human activities in the catchment was found at ca. 4 kyr BP in the form of increased erosion, associated with a decline in the abundance of biological remains. Further signs of human impact on the lake ecosystem are recorded during the Roman period. Although large-scale environmental changes (e.g. regional climate changes) caused many of the observed biological changes, human activities were important during the mid-late Holocene.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1573-2932
    Schlagwort(e): Acid deposition ; freshwaters ; nitrate ; nitrogen deposition ; Great Britain
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Energietechnik
    Notizen: Abstract A national dataset of water chemistry collected for critical loads mapping is used to make a regional assessment of surface water nitrate concentrations in Great Britain. The primary data are dominated by high concentrations in lowland regions Where N inputs are dominated by non-atmospheric sources. Land cover data are used to screen out sites with potential catchment sources of N, allowing the evaluation of nitrate leaching due to atmospheric deposition alone. In the screened dataset several upland regions show elevated nitrate concentrations, notably Wales, the Pennines, Cumbria, Galloway and the Cairngorms, and there is a clear relationship between surface water nitrate and total N deposition.
    Materialart: Digitale Medien
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