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  • 1
    Electronic Resource
    Electronic Resource
    Seasonal variation in pigmentation of the dinoflagellate Peridinium gatunense (Dinophyceae) in Lake Kinneret, Israel (2003)
    Oxford, UK : Blackwell Publishing
    Freshwater biology 48 (2003), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Pigment composition was measured in natural phytoplankton samples from Lake Kinneret, Israel. From March through June 1998, the dinoflagellate Peridinium gatunense Nygaard mostly contributed more than 95% of the algal biomass. Peak densities were found in April, close to the water surface, with 〉109 cells m−3, chlorophyll (Chl) a concentration of 380 mg m−3 and areal Chl-a density of 〉1300 mg m−2.2. Cellular concentrations of Chl-a changed between 201 and 282 pg cell−1, but did not show a defined temporal fluctuation.3. The mass ratio of Chl-c to Chl-a changed from March to June between 0.16 and 0.22, and the peridinin to Chl-a ratio changed from 0.25 to 0.41. Neither ratio showed a clear pattern of seasonal change. Conversely, there was a progressive increase in diadinoxanthin and β-carotene ratios to Chl-a through the season, parallel to the increase in photon flux impinging upon the lake surface. The diadinoxanthin to Chl-a ratio changed from 0.11 to 0.28 and the β-carotene to Chl-a ratio varied from 0.03 to 0.08 from March through June.4. Diatoxanthin was not detected in natural samples. However, it was present in experiments with P. gatunense cultures, when concentration of diatoxanthin increased rapidly, concurrent with a decrease in diadinoxanthin and β-carotene concentrations, while Chl-c and peridinin ratios to Chl-a were almost stable with photon flux increase.5. The seasonal variation in cellular pigmentation of P. gatunense in Lake Kinneret suggests that accumulation of photoprotective pigments is essential for optimisation of photosynthetic activity of this large dinoflagellate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2003.01135.x
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  • 2
    Electronic Resource
    Electronic Resource
    Distribution fields for aquatic ecosystem components: method of identification of correlation zones (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 34 (1995), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Data from the two multidisciplinary surveys of Lake Kinneret (Israel), including acoustic surveys of fish concentrations and concurrent sampling of plankton at stations, were used to reconstruct fish and plankton distributions. No significant lake-wide correlations for the distribution fields were found. With respect to patchiness of the fish and plankton distributions, we hypothesized that they might be correlated in localized zones.2. A method is suggested for the identification of areas where there are strong correlations of two distribution fields. The method is based on outlining zones where the gradients of the two fields of interest are in the same direction (or are opposite). Only areas larger than the autocorrelation circles (or ellipses) for the fields are considered. The correlation of the fields is calculated for each of the zones selected.3. The method was used in analysing data from the multidisciplinary surveys. We were able to detect areas of the lake where there were correlations for fish and plankton distributions. Analysis of specific conditions inside the correlation zones made it possible to construct hypotheses concerning the causes for the observed patterns of fish and plankton distributions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1995.tb00891.x
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  • 3
    Electronic Resource
    Electronic Resource
    Lake Kinneret phytoplankton: Stability and variability during twenty years (1970–1989) (1992)
    Springer
    Aquatic sciences 54 (1992), S. 104-127 
    Details
    ISSN: 1420-9055
    Keywords: Lake Kinneret ; phytoplankton ; algal biomass ; chlorophyll ; succession
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The general features of phytoplankton seasonal succession, abundance and distribution in Lake Kinneret, as based on observations from 1970 through 1989, are summarised. Throughout this period of observation, the large, thecate dinoflagellatePeridinium gatunense formed an annual, late winter to early spring bloom resulting in very high standing stock levels. The dominance of these dinoflagellates has a profound impact upon the lake ecosystem. In the summer and fall the phytoplankton assemblage consisted mainly of nanoplanktonic green and blue-green algae and diatoms. Picophytoplankton, mainly picocyanobacteria, were present in low numbers during the dinoflagellate bloom but reached maximum abundance (105 cells · ml−1) in the epilimnion during the summer and fall. Within a given year, chlorophyll concentrations correlated well with estimates of wet weight biomass, derived from microscope counts. However, interannual averages of chlorophyll did not correlate closely with those for wet weight biomass. Both wet weight biomass and chlorophyll standing stocks fluctuated more than 2 fold from 1970 through 1989 but no extreme, long-term, continuous trend of increase or decrease was observed. Thus, phytoplankton has remained relatively stable although there has been a significant rise in the levels of summer-fall biomass since 1981. The main factor responsible for this may have been increased available phosphorus; the abundance of phytoplankton did not show any clear, long-term relation to that of herbivorous zooplankton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00880278
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  • 4
    Electronic Resource
    Electronic Resource
    Genetic induction of bivalent interlocking in common wheat (1982)
    Springer
    Chromosoma 87 (1982), S. 165-175 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The frequency of interlocking bivalents at first meiotic metaphase of common wheat Triticum aestivum L., which is normally very low, is significantly increased by raising the dosage (from two to three, four and six) of the Ph1 gene, located on the long arm of chromosome 5B (5BL). In several cells more than three bivalents were interlocked in one chain configuration indicating involvement of non-homoeologous bivalents. Plants with reduced dose (one or zero) of Ph1 also exhibited an increased frequency of interlocking but to a lesser extent than those with high gene dosage. However, chains of more than three interlocked bivalents were never observed in these plants, suggesting that with one or zero doses of Ph1 interlocking is restricted to homoeologous bivalents only. Chromosomal arm 5BS affected interlocking in an opposite manner to 5BL; namely, two and four doses of 5BS markedly reduced interlocking frequency. The modification in the frequency of interlocking bivalents by these genetic manipulations represents the first successful attempt to affect interlocking by genetic means. The results are explained on the basis of the hypothesis that this gene system controls somatic and premeiotic association of both homologous and homoeologous chromosomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00338487
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  • 5
    Electronic Resource
    Electronic Resource
    An ordered arrangement of bivalents at first meiotic metaphase of wheat (1985)
    Springer
    Chromosoma 91 (1985), S. 347-354 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Distances between marked pairs of bivalents were determined at first meiotic metaphase of common wheat (2n=6x=42; genome AABBDD) by tallying the number of bivalents intervening between the marked bivalents. Bivalents of the same genome tended to lie relatively close to one another, whereas those of different genomes were further apart on the metaphase plate. Within each genome the association of telocentric bivalents representing the two different arms of one chromosome was much more intimate than that of genetically nonrelated bivalents. Among chromosomes of different genomes, homoeologous bivalents were relatively closer to one another than nonrelated ones. These results were more pronounced in cells with circularly arranged bivalents on the metaphase plate than in those with a linear arrangement. The data, consistent with previous findings in cold-treated somatic cells, indicate that a similar pattern of chromosomal arrangement exists in somatic and meiotic cells and that chromosomal arrangement observed in arrested metaphases is also maintained on the untreated, functional spindle system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00291006
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  • 6
    Electronic Resource
    Electronic Resource
    An ordered arrangement of bivalents at first meiotic metaphase of wheat (1985)
    Springer
    Chromosoma 91 (1985), S. 355-358 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The spatial relationships between different types of marked pairs of bivalents or trivalents were studied at first meiotic metaphase of tetraploid wheat (2n=4x=28; genome AABB) by tallying the number of intervening bivalents between the marked pair. The study was carried out only in pollen mother cells with circularly arranged metaphases. Telocentric bivalents representing the two different arms of one chromosome were found very close to each other. Nonrelated trivalents of the same genome were significantly closer to each other than nonrelated trivalents of different genomes. Homoeologous trivalents tended to lie relatively close to one another. This pattern of chromosomal arrangement agrees well with previous findings in hexaploid wheat, both in mitotic and meiotic cells. It is concluded that in polyploid wheat the chromosomes of each genome lie relatively close to each other and are spatially separated from those of the other genomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00291007
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  • 7
    Electronic Resource
    Electronic Resource
    High performance liquid chromatography detection of phototrophic bacterial pigments in aquatic environments (1990)
    Springer
    Microbial ecology 19 (1990), S. 127-136 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pigment extracts of phototrophic bacteria isolated from Lake Kinneret (Rhodopseudomonas palustris, Thiocapsa roseopersicina, Prosthecochloris aestuaris andChlorobium phaeobacteroides) were studied by means of high performance liquid chromatography (HPLC). An absorption wavelength of 360 nm provided the best resolution among the pigments of the species tested and between them and chlorophylla. Signature pigments were identified for each of these species, and their presence was thereby monitored in lake water samples.C. phaeobacteroides, which was observed in the anaerobic hypolimnion and predominated in the metalimnion, was recognized by a characteristic cluster of major chlorophyllous pigment peaks. The spectral qualities of these pigments were close but not identical to published data on bacteriochlorophylle, presumably due to the use of different solvents for extraction. The intensity of these pigment peaks was employed to determine the depth of the greatest phototrophic bacterial biomass, which was not related to that of algae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02012094
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  • 8
    Electronic Resource
    Electronic Resource
    Spatial distributions of biogeochemical parameters in surface sediments (1997)
    Springer
    Water, air & soil pollution 99 (1997), S. 497-505 
    Details
    ISSN: 1573-2932
    Keywords: surface sediments ; spatial distribution ; Chla &c ; C, N & P ; bacterial activity ; Lake Kinneret
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The spatial variability of several sedimentological, chemical and biological parameters in the uppermost layer of bed sediment (ULBS) in Lake Kinneret, was studied during the development of anoxic conditions in the hypolimnion (May, 1995). ULBS samples were taken along a transect from the littoral to the pelagic zones, during tile crash of thePeridmium gatunense bloom, about 2 months after the onset of stratification and when oxygen in the hypolimnion was almost completely depleted. The 2–3mm of the ULBS, collected by SCUBA diver, contained relatively fresh material (as shown by high Chl c content) but differed from that of intactPeridinium cells. In the ULBS, the C:N atomic ratio averaged 8 and was similar all over the lake bottom and the average Chlorophyll a c ratio was 4 (reaching a value of ∼7 at 5m). These ratios inPeridinium cells were about 14 3 and 2, respectively. In addition, δ12C in the organic matter from the ULBS was lighter than that ofPeridinium. This data suggests that substantial degredation of the organic matter already occurs in the water column. Grain size distribution suggests the occurance of intense focussing processes in Lake Kinneret. Chemical and biological parameters in the ULBS exhibited clear depth dependant patterns, suggesting changes in physical and chemical processes occur. Three different zones can be distinguished in Lake Kinneret bottom sediments a. The littoral oxic pholic zone (down to 5–7m), which is influenced by intensive biodegradation and high turbulence. b Transition zone (7–20m), with anoxic-photic gradient and developed focussing processes c. Profundal, anoxic zone (〉20m), where all line, settled, organic rich material concentrates and undergoes anaerobic decomposition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02406889
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