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1

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Sulfate reduction processes in sediments at different sites in Lake Kinneret, Israel (1995)

Hadas, O. ; Pinkas, R.

Springer

Microbial ecology 30 (1995), S. 55-66

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ISSN: 1432-184X

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Lake Kinneret, Israel, is a warm (13–30°C) monomictic lake that stratifies in April and turns over in December. Between January and June each year, a heavy bloom (up to 250 g wet weight n−2 2) of the dinoflagellate Peridinium gatunense dominates the phytoplankton biomass. In early summer, the bloom collapses, and the sinking Peridinium biomass serves as a trigger for intense sulfate-reduction activity throughout the hypolimnion and within the sediments. The availability of organic matter and sulfate was high shortly after the bloom crash and the beginning of stratification and was lowest in December before overturn. Sulfate-reduction rates at three different sites in the lake were studied. In the sediments, the rates varied seasonally and among stations from 5 to 1600 nmol SO4 −2 reduced cm−3 day−1, with respect to the distance from the Jordan River, depth, organic content, and stratification period. During years of low lake water levels, intense sulfate reduction occurred in the hypolimnion, resulting in anoxia and high concentrations of H2S (〉400 μm). In years with high water levels, early bloom, and delayed stratification, higher rates of sulfate reduction were recorded in the sediments, probably as a result of a greater fraction of the primary production (organic matter) reaching the bottom.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00184513

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2

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Nitrate reductase activity, ammonium regeneration, and orthophosphate uptake in protozoa isolated from Lake Kinneret, Israel (1992)

Hadas, O. ; Pinkas, R. ; Wynne, D.

Springer

Microbial ecology 23 (1992), S. 107-115

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ISSN: 1432-184X

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Nitrate reductase (NR) activity and nutrient (N, P) recycling in the ciliatesColpoda steinii andStylonychia sp. and two unidentified flagellates (I and II), isolated from Lake Kinneret, have been studied. When grown on a bacterium also isolated from the lake, all species, except flagellate I, exhibited NR activity. Activity was higher in the presence of nitrate than in its absence, and in the case ofC. steinii showed a dependence on initial ambient NO3 concentrations in the cultures. NR activity was inversely proportional to body size, suggesting that the larger protozoan species have decreased specific metabolic rates. A net increase in ammonium concentrations and a decrease in orthophosphate levels was observed, but both phenomena were much less sensitive to ambient NO3 concentrations than NR activity. Similar trends in NR activity and NH4 production were also observed whenC. steinii was grown on the picocyanobacteriumSynechococcus sp. Our results suggest that NH4 excretion is the outcome of N remineralization from the food supply but is also partially due to dissimilatory nitrate reduction. These data imply that protozoa may have an important role in nutrient recycling in Lake Kinneret and that some species could use NO3 respiration in anoxic regions of the water column.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00172633

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3

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Heterotrophic activity, glucose uptake and primary productivity in Lake Kinneret (1979)

CAVARI, B. Z. ; HADAS, O.

Oxford, UK : Blackwell Publishing Ltd

Freshwater biology 9 (1979), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: SUMMARY. Chlorophyll, ATP and glucose concentrations as well as glucose uptake rate and primary production were determined every 2–4 h during three 24–h surveys in Lake Kinneret. In spite of the fluctuations in glucose uptake rate, the estimation of the daily glucose uptake rate from a single sampling carried out at 10.00 hours is justified. The same applies also for the primary production.Routine bi-weekly determinations of primary production and glucose uptake rate were carried out from October 1976 to July 1977. No correlations were found between glucose uptake rates and ambient concentrations of ATP, chlorophyll and glucose.The glucose uptake rate showed two distinct seasonal patterns; the period which was dominated by the Peridinium (January-April) and the rest of the year. In the former period the percentage of glucose-carbon utilized out of the carbon formed in the water column by the photosynthetic activity, fluctuated between 1 and 9%, and in the latter period fluctuated between 5 and 37%. The yearly average was 11.1%, SD 9.8.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-2427.1979.tb01517.x

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4

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Sulphate reduction in the hypolimnion and sediments of Lake Kinneret, Israel (1995)

HADAS, O. ; PINKAS, R.

Oxford, UK : Blackwell Publishing Ltd

Freshwater biology 33 (1995), S. 0

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ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 1. Lake Kinneret is a warm (13–30°C) monomictic lake. Between January and June a heavy annual bloom of the dinoflagellate Peridinium gatunense dominates phytoplankton biomass (250 g m−2). At the beginning of the summer, degradation and decomposition of the Peridinium biomass occurs, serving as a trigger for intense sulphate reduction in the hypolimnion and sediments.2. The rates of sulphate reduction in the sediments varied seasonally from 12 to 1700 nmol SO4.−2 reduced cm−3 day−1 in December and July, respectively. The availability of organic matter and sulphate is high in June after the crash of the Peridinium bloom and the beginning of stratification and is lowest in December before overturn.3. Sulphate concentrations in the hypolimnion range between 0.52 mM and 0.20 mM during mixing (January-April) and before overturn (December), respectively. The depletion in sulphate in the hypolimnion is stoichiometrically correlated to the increase in sulphide. The lake is not depleted of sulphate at any time, so the sulphate reduction process in Lake Kinneret is not limited by sulphate concentrations except in the sediments just before overturn.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-2427.1995.tb00386.x

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5

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Preferential feeding behaviour of Daphnia magna (1982)

Hadas, O. ; Cavari, B. Z. ; Kott, Y. ; [et al.]

Springer

Hydrobiologia 89 (1982), S. 49-52

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ISSN: 1573-5117

Keywords: Daphnia ; algal - bacterial ; consumption

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Preferential feeding behaviour by Daphnia magna was shown when Daphnia were fed on a mixture of 14C-labelled algae (Chlorella vulgaris or Scenedesmus quadricauda) and 3H-labelled bacteria (Escherichia coli). Daphnia consumption of bacteria was equal or higher in the presence of algae. On the other hand, in the presence of bacteria, algal consumption decreased by 40–70% compared to algal consumption in the absence of bacteria. 14C radioactive uptake was in good agreement with the chlorophyll content and demonstrates the preferential feeding behaviour of Daphnia.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00017537

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6

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Heterotrophic glucose uptake and respiration in Lake Kinneret (1979)

Berman, T. ; Hadas, O. ; Marchaim, U.

Springer

Hydrobiologia 62 (1979), S. 275-282

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ISSN: 1573-5117

Keywords: Lake Kinneret ; Glucose heterotrophy ; Glucose Respiration

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The turnover times of glucose, averaged for 0–10 m in the upper waters of Lake Kinneret and measured by the addition of single or multiple concentrations of substrate, ranged from 23 to 188 hours and 1 to 87 hours respectively. Potential uptake rates (estimated as Vmax) ranged from 0.095 to 1.94 µg glucose l−1h−1, while measured uptake rates varied from 0.09 to 1.1 µg glucose l−1h−1. Concentrations of dissolved carbohydrates and glucose averaged 0.71 mg glucose equivalents l−1 and 39 µg glucose l−1 respectively. No evident relationships between glucose cycling and any fractions of dissolved organic matter, phytoplankton biomass or primary productivity were found. Turnover times were generally most rapid immediately after the decline of the spring Peridinium bloom. The respiration percentage of incorporated glucose ranged from 25% to 61% with highest values during the summer months. Respiration may be influenced by the nature of the indigenous bacterial population as well as by temperature. Daily heterotrophic glucose carbon uptake was about 9% of the photosynthetic incorporation and could provide a bacterial yield of about 7 × 104 ml−1d−1.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00043545

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7

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Assimilation of E. coli cells by Daphnia magna on the whole organism level (1983)

Hadas, O. ; Bachrach, U. ; Kott, Y. ; [et al.]

Springer

Hydrobiologia 102 (1983), S. 163-169

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ISSN: 1573-5117

Keywords: Daphnia ; E. coli ; lysis ; antibiotics ; microflora ; assimilation

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Consumption of E. coli cells by Daphnia magna was studied. It was found that this organism not only ingested E. coli cells but digested them as demonstrated by the release of 14CO2 originating from E. coli grown on 14C-glucose, and by the transfer of the radioactive label from parental Daphnia to their progenies. In addition the effect of antibiotics on the consumption of E. coli cells by Daphnia magna was studied. In long incubation times, antibiotics inhibited bacterial uptake by Daphnia. The microflora isolated from Daphnia was found to be capable of causing leakage of enzymes out of E. coli cells thus playing at least a partial role in the digestion of E. coli cells by Daphnia.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00006343

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8

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Arylsulfatase and Alkaline Phosphatase (APASE) Activity in Sediments of Lake Kinneret, Israel (1997)

Hadas, O. ; Pinkas, R.

Springer

Water, air & soil pollution 99 (1997), S. 671-679

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ISSN: 1573-2932

Keywords: Alkaline phosphatase ; arylsulfatase ; sediments

Source: Springer Online Journal Archives 1860-2000

Topics: Energy, Environment Protection, Nuclear Power Engineering

Notes: Abstract Arylsulfatase and APase activities were monitored in the upper sediment layer, of Lake Kinneret, Israel, a warm, freshwater, monomictic lake characterized by a heavy spring bloom of the dinoflagellate Peridinium gatunense. Activity of both enzymes varied with depth and season. Highest activity was measured in July and high activities were monitored during the stratified period. Low values were observed in winter, when oxic conditions prevail in the water column and no organic sedimentation occurred. The values for APase ranged from 14-438 nmol PNP g-1h-1 and for arylsulfatase from 103 to 843 nmol PNP g-1h-1. Highest APase activity was recorded at 29°C, and most of it took place on mud particles and not in the interstitial waters. There were differences in enzyme activity at different stations in the lake, corresponding to differences in nutrient pore water concentrations. Enzymatic activity in Lake Kinneret sediments was related to lake trophic status, water levels, and climate conditions, all of which have an impact on the amount of organic matter reaching the sediments.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1018388817351

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Occurrence of non-cylindrospermopsin-producing Aphanizomenon ovalisporum and Anabaena bergii in Lake Kinneret (Israel) (2011)

Ballot, A., Ramm, J., Rundberget, T., Kaplan-Levy, R. N., Hadas, O., Sukenik, A., Wiedner, C.

Oxford University Press

In: Journal of Plankton Research

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Publication Date: 2011-11-24

Description: The cylindrospermopsin (CYN)-producing cyanobacterium Aphanizomenon ovalisporum is currently known from the Mediterranean area of Europe and the Middle East and from North America and Australia. Aphanizomenon ovalisporum was observed for the first time in Lake Kinneret (Sea of Galilee, Israel) in 1994. It appeared with an exceptional bloom and has persisted since then. To gain further insight into biodiversity and chemotype composition of this invasive cyanobacterium, we isolated, cultured and analyzed six putative A. ovalisporum strains from Lake Kinneret in 2010. In a polyphasic approach, the strains were investigated for their morphology and phylogeny (based on 16S rRNA gene and PC-IGS) as well as for CYN production [by enzyme-linked immunosorbent assay (ELISA) and LC-MS] and the presence of four fragments of the CYN-encoding gene cluster (aoaA/ cyrA , aoaB/ cyrB , aoaC/ cyrC and cyrJ ). Two isolated strains were assigned to A. ovalisporum , whereas four strains were identified as Anabaena bergii . Unlike previous reports of toxic A. ovalisporum from Lake Kinneret, all strains isolated in this study tested negative for CYN by ELISA and LC-MS. All strains contained aoaA/ cyrA , aoaB/ cyrB and aoaC/ cyrC fragments of the CYN gene cluster. The cyrJ fragment was not detected in any of the isolated strains. This is the first report describing non-CYN-producing A. ovalisporum strains and the presence of the cyanobacterium A. bergii in L. Kinneret.

Print ISSN: 0142-7873

Electronic ISSN: 1464-3774

Topics: Biology