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1.
Heikki Simola 《Journal of Paleolimnology》1991,6(3):257-260
The utility of classifying chrysophyte stomatocysts by their characteristic honeycomb and ridge patterns is questioned, because a strikingly similar expanding pattern appears on the surface of ionized polymer gels during osmotical swelling as a result of simple physical forces. The rapid accumulation of silicate into a spherical cyst inside a chrysophyte cell appears to be as a physical process sufficiently similar to result in an analogous pattern in microscopic scale. Chrysophyte stomatocysts that possess honeycomb or ridge patterns could be regarded as frozen moments of the pattern evolution during the silicate gel phase. As a consequence, such structures should have little taxonomical value. 相似文献
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Alena FIRSOVA 《《地质学报》英文版》2014,88(Z1):68-69
正The chrysophytes are distributed over all the continents.As a rule,these are planktonic,freshwater,cold-water inhabitants.There are as well saltish-water chrysophytes species of genera Chrysococcus,Dinobryon, 相似文献
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Chrysophycean stomatocysts were identified and enumerated from the surface sediments of 60 lakes located on the Interior Plateau of British Columbia. The lakes span a salinity gradient from freshwater to hypersaline (0.0–92.4 g L–1), with the majority being fresh to hyposaline. One hundred and ten stomatocyst morphotypes, almost all of which were previously described, were identified from the lake sediments. The first axis of direct gradient analysis, which was highly significant, was essentially a salinity axis (i.e. [Ca], [Mg], [K], [Na], [SO4], [DIC], and [Cl]). Most cysts were found to have fairly broad tolerances, with the narrowest tolerances occurring among morphotypes with the lowest salinity optima. Weighted-averaging regression and calibration techniques were used to develop an inference model to measure the relationship between measured average lakewater salinity and stomatocyst inferred salinity (apparent r2=0.80). Simple weighted-averaging produced a model with a lower bootstrapped RMSE of prediction than weighted-averaging with tolerance downweighting. These data indicate that chrysophyte stomatocysts are useful quantitative indicators of past lakewater salinity (in the freshwater to hyposaline range) in B.C. lakes, and can be used to strengthen the interpretations from diatom-inference models already developed from the same region. 相似文献
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Diatom and chrysophyte cyst-based reconstructions of the dates of spring and autumn lake-mixing enabled us to estimate spring
(STanom) and autumn (ATanom) temperature anomalies as well as ice-cover of the last ca. 4,000 years in a lake sediment core (Oberer Landschitzsee, 2,076
m a.s.l.) from the southern slopes of the Austrian Central Alps. The two independently inferred temperature anomalies were
significantly correlated. On average, spring and autumn temperatures were lower during the two millennia B.C than during 0–1,300
A.D. Marked spring and autumn temperature minima occurred at about 1,300 and 600 B.C. At about 1,300 A.D, STanom declined again. Spring-temperature anomalies during Roman and Medieval times equaled or slightly exceeded the modern values
and paralleled tree-line and glacier fluctuations. The de-coupling of autumn and spring climates, which began during the Medieval
period, might indicate changes in major circulation modes. It was assumed that the North-Atlantic influence, triggering winter-rain
climate in the Northern Mediterranean, became weaker during Medieval times, resulting in a trend towards warmer autumns and
overall more continental climate conditions in the study area. Four pulses of land use, inferred from indicator pollen, occurred
during (1) the Early to Late Bronze, (2) the transition from Late Bronze to Early Iron Age (Hallstatt), (3) Late Iron Age
(La Tène, Celtic time) to Roman times, and (4) during high to late Medieval times. Climate seemed to be an important, though
complex, trigger of Alpine land use. 相似文献
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We examined changes at the community and population level of sedimentary diatoms over a wide temporal and spatial gradient
of metal pollution encountered in cores from three lakes in the Abitibi mining region (Québec, Canada). Diatom communities
on the whole appeared to be very tolerant of metal contamination, as shown by diatom cell accumulation rates decreasing only
under the most severe conditions of contamination, which were found from the 1930s to the 1980s in Lac Dufault (cadmium, up
to 94 μg/g dry sediment; Cu, up to 8600 μg/g; Zn, up to 9000 μg/g). Under the moderate conditions of contamination observed
in the other two lakes and in the most recent sediment of Lac Dufault, diatom cell accumulation rates tended to increase over
values typical of the pre-mining period. However, there were increasing rearrangements of the community composition along
the contamination gradient. Under moderate metal enrichment, the diatom community of Lac Vaudray experienced only subtle changes,
with Cyclotella stelligera, albeit decreasing, remaining the dominant taxon. In the intermediately contaminated Lac Caron, several benthic taxa, noticeably
Cymbella silesiaca and several Fragilaria species, rose in taxonomic importance. The most extreme contamination observed in Lac Dufault led to a severely impoverished
community almost entirely represented by Achnanthes minutissima and Brachysira vitrea. With increasing levels of contamination, there was a shift from planktonic to benthic taxa and morphotypes and a consistent
decrease in the siliceous stomatocysts/diatom frustules ratio. These trends suggest that littoral zones may represent an
important refugium under conditions of high contamination. Responses to metal stress were in general more evident at the population
than at the community level. Cyclotella stelligera and B. vitrea had a consistent negative and positive response, respectively, along the gradient and are the most promising indicators of
metal pollution for this region. 相似文献
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Fairfax Lake is a small, oligotrophic to mesotrophic headwater lake situated in the Foothills of the Rocky Mountains of west-central Alberta (Latitude 52° 58 N; Longitude 116° 34 W). Through acquisition of a sediment core, and analyses of the diatoms, chrysophyte stomatocysts, pollen and sedimentary pigments, including myxoxanthophyll and oscillaxanthin, a palaeoenvironmental history of the lake has been determined. The sedimentary record spans ca. 13 200 years. An open tree-less vegetation existed in the region ca. 13 200–ca. 11 600 years BP. Maximum oscillaxanthin and myxoxanthophyll concentrations, hence the largest blue-green algal populations, occurred during the same interval. With increasing temperature pioneering parkland vegetation appeared ca. 11 600 years BP but was replaced ca. 10 100 years BP by spruce forest. Pine appeared ca. 7800 years BP and this marked the development of the present day montane boreal forest. Diatoms were not found until ca. 11 255 years BP. Benthic taxa dominated but by ca. 10 100 years BP planktonic taxa had become more prominent. Lake levels are interpreted as having risen, and the lake water was probably more transparent. Maximum chlorophyll and total carotenoid concentrations occur ca. 11 255 to ca. 7000 years BP corresponding to the warm early to mid-Holocene period. Lake nutrient levels appear to have been higher prior to ca. 7000 years BP, and the lake has changed from being eutrophic during the early Holocene to its present status as an oligotrophic to mesotrophic lake. Subtle hydrological changes have also occurred in the catchment as water levels do not appear to have remained constant. 相似文献
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F. Šporka E. Štefková P. Bitušík A.R. Thompson A. Agustí-Panareda P.G. Appleby J.A. Grytnes C. Kamenik I. Krno A. Lami N. Rose N.E. Shilland 《Journal of Paleolimnology》2002,28(1):95-109
Sedimentological climate proxies and a 200-year long climate record, reconstructed using a data-set of European-wide meteorological data, have been compared at the high mountain lake Niné Terianske pleso in the High Tatras, Slovakia. Diatoms, chrysophyte stomatocysts, chironomids, plant pigments and spheroidal carbonaceous particles (SCPs) were analysed as well as sediment lithostratigraphic parameters. Using a radiometric approach the sediment core was dated and a depth of 4.6 cm was found to correspond to 1852 AD. The sediment accumulation rate (0.0034 g·cm–2·yr–1) was one of the lowest identified in the European mountain lake project, MOLAR. Despite this slow accumulation rate a remarkably coherent lithological and stratigraphic record has been recovered. The sediments of this remote mountain site, largely free from the effects of direct human impact, have been found to display a wealth of variability over the last 200 years.The record of spheroidal carbonaceous particles, indicators of anthropogenic pollution deposition, begins around 4.5–5.0 cm in depth (1833–1857). Temporal patterns are typical of European lake sites with the concentration peaking in the late 1970's. The SCP/210Pb inventory ratio for the site is also in good agreement with the European latitudinal pattern. A strong influence of sample age on the chrysophyte assemblage composition in the upper-most 4–6 cm indicates that the main changes in the cysts have been related to long term environmental changes, probably pH. Analysis of chironomid remains revealed a stable profundal community. Chironomids as a whole showed no correlations to temperature fluctuations in the last 200 years. Relatively abundant remains of Diamesa sp. head capsules and other taxa closely associated with stream conditions in the older layers contrast with the absence of Diamesa sp. in the recent sediments. This change is considered to be evidence for the existence of a stronger, more stable inlet supplied from permanent granular snow fields in the lake basin. The most important changes in diatom assemblages were observed at 3cm. Many species of the genus Achnanthes spp. together with Navicula schmassmannii and Orthoseira roeseana made up the greatest part of the diatom community above 3 cm, being absent or rare lower in the record. A positive correlation between diatoms and mean summer temperature was found. 相似文献
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The chrysophycean stomatocyst flora from the sediments of Upper Wallface Pond, a recently acidified Adirondack lake, was described according to the guidelines of the International Statospore Working Group. Sixty-six morphotypes were distinguished, using scanning electron microscopy. Twenty-eight of these cysts were distinguishable using the light microscope (LM), whereas 30 required grouping into 11 collective categories from LM identification, and 7 could not be identified using LM. None of our morphotypes could be linked definitively to the living chrysophyte species that produced them. Stratigraphic analysis showed that a marked change in the cyst assemblage occurred in the 1930's. Previous paleoecological studies inferred a pronouced pH decline at this time. Redundancy analysis of our data showed that diatom-inferred pH explained a significant amount of variation (Monte Carlo permutation test; p=0.01). This suggests that pH influences chrysophyte populations, and that stomatocysts could eventually be used to reconstruct pH and other variables.This is the fourth in a series of four papers published in this dedicated issue entitled Application of Chrysophyte Stomatocysts in Paleolimnology. Dr. C. D. Sandgren served as guest editor for these papers. 相似文献