Sándor Herodek

Hungarian Academy of Sciences, Budapeŝto, Budapest, Hungary

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Publications (36)42.45 Total impact

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    Tóth VR · Sandor Herodek
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    ABSTRACT: Abiotic heterogeneity of the littoral zone of Lake Balaton influences both horizontal and vertical distribution of macrophytes, but biotic differences could shape the nature of a community. Vertical and temporal (small timescale) biomass distributions of Potamogeton perfoliatus and Myriophyllum spicatum were analysed in relation to their photosynthetic capacities to understand their coexistence and the general presence over the northern shore of the lake seasonal shift of dominance within the community. Our results indicated the adaptation of these macrophytes to the rapidly changing and mostly low irradiance of the Lake Balaton originated from its high turbidity: both P. perfoliatus and M. spicatum had high photosynthetic activity (20 to 50 mg O2 g[drw]-1 h-1), low dark respiration (around 12-14% of maximal photosynthetic capacity) and high shade tolerance (Ic of plants were 29±18 and 26±18 mol m-2 s-1, respectively). The majority of photosynthetic parameters had no (or little) seasonal changes. On the other hand, in Lake Balaton P. perfoliatus and M. spicatum differed in vertical distribution of biomass: watermilfoil concentrated its biomass in the upper, well-lit region of the water more strongly than the pondweeds. Results suggest that the autogenic shift of dominance from Potamogeton to Myriophyllum in Lake Balaton can’t be explained only by seasonal patterns of photophysiological changes, but supported by constitutive differences in plants architecture could led to the described phenomena.
    Full-text · Article · Jan 2011 · Annales de Limnologie - International Journal of Limnology
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    ABSTRACT: The aim of this research was to test whether NH4 + and NO3 − affect the growth, P demand, cell composition and N2 fixation of Cylindrospermopsis raciborskii under P limitation. Experiments were carried out in P-limited (200 μg l−1 PO4-P) chemostat cultures of C. raciborskii using an inflowing medium containing either 4,000 μg l−1 NH4-N, 4,000 μg l−1 NO3-N or no combined N. The results showed the cellular N:P and C:P ratios of C. raciborskii decreased towards the Redfield ratio with increasing dilution rate (D) due to the alleviation of P limitation. The cellular C:N and carotenoids:chlorophyll-a ratios also decreased with D, predominantly as a result of an increase in the chlorophyll-a and N content. The NH4 + and NO3 − supply reduced the P maintenance cell quota of C. raciborskii. Consequently, the biomass yield of the N2-grown culture was significantly lower. The maximum specific growth rate of N2-grown culture was also the lowest observed. It is suggested that these differences in growth parameters were caused by the P and energy requirement for heterocyte formation, nitrogenase synthesis and N2 fixation. N2 fixation was partially inhibited by NO3 − and completely inhibited by NH4 +. It was probably repressed through the high N content of cells at high dissolved N concentrations. These results indicate that C. raciborskii is able to grow faster and maintain a higher biomass under P limitation where a sufficient supply of NH4 + or NO3 − is maintained. Information gained about the species-specific nutrient and pigment stoichiometry of C. raciborskii could help to access the degree of nutrient limitation in water bodies.
    No preview · Article · May 2009 · Hydrobiologia
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    Tóth VR · Sándor Herodek
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    ABSTRACT: The aim of the study was to design and put together a compact, easy-to-assemble and costefficient incubation system for aquatic plant photosynthesis measurements. Incubation tank consisting of glass sidewalls and mirror inner walls was constructed. The tank was split into six incubation cells and two water collecting cells. Each incubation cell was built of mirror with reflective side turned into the incubation cells to prevent the self shading of plants and minimized the variance of light intensity within the cell. The wall of each incubation cell facing the source of light was made of 3 mm glass and was covered by light absorbing film. To produce different light intensities single light source (fluorescent tubes) and light absorbing film (3M Scotchtint™ Sun Control RE50NEARL) were chosen. The sidewall of each incubation cell was covered with metal-coated neutral sun control film to produce six distinct light intensities. The different transparency of the sidewalls was achieved by lamination of the chosen film in increasing numbers of layers. The effect of the lamination on optical properties of the film was also studied. The variation of photon flux density within a cell was 3.9%. Continuous use of the system and occasional repetitive measurements of film's transparency showed that it maintained its neutral optical properties over a long period of time.
    Full-text · Article · Jan 2009 · Annales de Limnologie - International Journal of Limnology
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    ABSTRACT: A competition experiment was performed in chemostat cultures with different nutrient treatments using phytoplankton from Lake Balaton, Hungary. The inflowing medium was natural lake water enriched with orthophosphate at a concentration of 100 μg l−1. In the continuous supply culture (CS) the ammonium concentration of the inflowing medium was 200 μg.l−1. Ammonium was injected once daily in the pulsed supply culture (PS). The third culture was run with no N supply (NNS). Large cell volume algae had been excluded from each culture for one to two weeks. Planktolyngbya subtilis was dominant in the CS. Its success may have depended more on the mode of nutrient supply, through a lower half saturation constant, than on nitrogen limitation. In the PS, Nitzschia spp. were the dominant algae along with some Chlorophyta, which may be the result of a high silicon concentration. The results of NNS show that algae could not grow in the culture without ammonium addition. Ammonium uptake in the CS and the PS was measured with 15N methodology at the end of the experiments. The KS and Vmax values were twice as high in the PS (18.7 μg.l−l and 85.1 μg.l−l.h−1) as in the CS (9.2 μg.l−l and 40.8 μg.l−l.h−1). But the ratios of kinetic parameters (α = Vmax/KS) were very similar in the CS and the PS.
    No preview · Article · Apr 2004 · Algological Studies
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    ABSTRACT: Ammonium and nitrate uptake and N2-fixation of the heterocystous cyanoprokaryote Cylindrospermopsis raciborskii was examined in continuous cultures under different nitrogen concentrations and dilution rates using the 15N technique. It was found that at luxury phosphorus supply (5 mg PO4-P l–1) the biomass was similar in all cultures irrespective of the amount and portioning (continuous or pulsed) of available nitrogen forms. The added ammonium and nitrate was fully taken up by C. raciborskii and the remaining nitrogen demand was met by N2-fixation. Different ammonium concentrations (300, 750, 1500 and 3000 g 15N l–1) added at the same dilution rate did not affect the growth of C. raciborskii. In the culture supplied with pulsed ammonium, N2-fixation was detected prior to ammonium addition only. After the ammonium pulse, the N2-fixation continued for a while then decreased and stopped. In addition, the inflowing ammonium was fully taken up by the organism. The rate of nitrogen fixation reached its original level after 8–24 hours, depending on the dilution rate. It can be suggested that the nitrogen fixation system stopped and was then activated again depending on the nitrogen content of the cells.
    No preview · Article · Oct 2003 · Hydrobiologia
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    Mátyás Présing · Sándor Herodek · Tom Preston · Lajos Vörös
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    ABSTRACT: 1. The importance of various forms of nitrogen to the nitrogen supply of phytoplankton has been investigated in the mesotrophic eastern and eutrophic western basin of Lake Balaton. 2. Uptake rates of ammonium, urea, nitrate and carbon were measured simultaneously. The uptake rates were determined using N and C methodologies, and N2-fixation was measured using the acetylene-reduction method. The light dependence of uptake was described with an exponential saturation equation and used to calculate surface-related (areal) daily uptake. 3. The contribution of ammonium, urea and nitrate to the daily nitrogen supply of phytoplankton varied between 11 and 80%, 17 and 73% and 1 and 15%, respectively. N2-fixation was negligible in the eastern basin and varied between 5 and 30% in the western region of the lake. The annual external nitrogen load was only 10% of that utilized by algae. 4. The predominant process supplying nitrogen to the phytoplankton in the lake is the rapid recycling of ammonium and urea in the water column. The importance of the internal nutrient loading is emphasized.
    Full-text · Article · Dec 2000 · Freshwater Biology
  • M. Présing · S. Herodek · L. Vörös · T. Preston · G. Abrusán
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    ABSTRACT: The contribution of ammonium, nitrate and N2 to the nitrogen demand of summer phytoplankton has been estimated in two basins of Lake Balaton. The uptake rates of ammonium and nitrate were determined using 15N methodology. N2-fixation rates were measured by the acetylene-reduction technique. The light dependence of uptake and N2-fixation was described with an exponential saturation equation. The decrease of I(k) values from mid-summer to autumn coincided with an increasing contribution of cyanobacteria to the algal population, suggesting a relatively lower light requirement than that of other species. The dark uptake velocity of ammonium and nitrate were 30-63 % and 1-40 % of light saturated uptake, respectively. The contribution of ammonium to the daily nitrogen supply of algae varied between 50-90 %. Nitrate uptake was much less important with a maximum of 40 %. Nitrogen fixation was significant only in the western basin at the time of highest primary production and greatest N2-fixing cyanobacterial contribution. Nitrogen uptake experiments and loading data suggest, that nitrogen regeneration is by far the most important process in establishing and supporting the standing crop of phytoplankton in the lake during summer.
    No preview · Article · Apr 1999 · Archiv fur Hydrobiologie
  • M. Présing · L. Vörös · S. Herodek · G. Abrusán
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    ABSTRACT: The contribution of nitrogen forms to the nitrogen demand of phytoplankton has been estimated in two basins of the oligo-mesotrophic Lake Balaton and its two hypertrophie pollution control reservoirs. The uptake rates were determined using 15N methodology, and by measuring concentration changes with time. N2-fixation were measured by the acetylene-reduction technique. The light dependence of uptake and N2-fixation was described with an exponential saturation equation. The dark uptake velocity of ammonium, nitrate and urea were 60-80%, 4-66% and 16-74% of light-saturated uptake, respectively. Ammonium, urea and nitrate uptakes were 51-85%, 12-42% and 2-8% of the total daily nitrogen uptake. In contrast, N2-fixation was insignificant (0-4%). The interaction of ammonium and nitrate uptake was determined in separate experiments, which demonstrated suppression of nitrate uptake at ammonium addition.
    No preview · Article · Jan 1998
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    ABSTRACT: The growth and cell composition of C. meneghiniana in P-, N- or Si-limited continuous cultures under different dilutions are discussed. Carbon, nitrogen and phosphorus content per cell or per unit cell volume increased with growth rate in all chemostats. Maximum growth rate depends on the type of limiting nutrient. The maximum growth rates are. 1.65 ± 0.04, 0.73 ± 0.07 and 0.95 ± 0.08 d-1 for P-, N- and Si-limited cultures respectively. These values are close to those calculated by Droop, Caperon, Goldman and Monod models. The concentrations of N and P in the river Danube are much higher than the requirements for growth and uptake of C. meneghiniana. This indicates that neither P nor N are limiting to the growth of C. meneghiniana in natural habitat.RésuméLa croissance et la composition cellulaire de C. meneghiniana soumis à des concentrations limitantes en P, N et Si en culture continue à des taux de dilution différents sont discutés. Le contenu cellulaire en carbone, azote et phosphore par cellule ou par unité de volume augmente avec le taux de croissance dans toutes les conditions précitées. Le taux maximum de croissance dépend du type de nutriment limitant. Ces valeurs sont très proches de celles calculées à partir des modèles de Droop, Caperon, Goldman et Monod. Dans le Danube, les concentrations en N et P sont beaucoup plus élevées que les besoins pour la croissance et l'assimilation de C. meneghiniana. Cela indique que ni N ni P ne sont limitants pour la croissance de C. meneghiniana en milieu naturel.
    Preview · Article · Nov 1997 · Annales de Limnologie - International Journal of Limnology
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    ABSTRACT: A strain of Cyclotella meneghiniana was isolated from the River Danube. The optimum irradiance and temperature for growth were determined in batch cultures. The optimum temperature for growth was 25 °C. The estimated saturated irradiance was near 125 µE m-2 s-1. The calculated Ik for growth and photosynthesis were 30 ± 3 and 44 ± 6 µE m-2 s-1 respectively. A continuous culture technique was used to test the growth and cell composition at the transition state between batch, nutrient sufficiency, and a low rate of nutrient supply. Algal response was characterized by high intracellular N and C with negative growth rate. At a low dilution rate (0.06 d-1), the continuous culture theory was not followed. This critical rate is characterized by low chlorophyll-a content per cell and may depend on the mode of nutrition. Une souche de Cyclotella meneghiniana, provenant du Danube, a été isolée. La température et la lumière optimales pour la croissance ont été déterminées en culture «batch» : 25°C et 125 µEm-2 s-1. L'Ik calculé pour la croissance et la photosynthèse était respectivement de l'ordre de 30 ± 3 et de 44 ± 6 µE m-2 s-1. La technique de la culture en continu a été également utilisée avec un faible apport de nutriments, correspondant à un stade en culture «batch» où les nutriments étaient encore non limitants. La réponse de la diatomée était caractérisée par un quota cellulaire de N et P élevé avec un taux de croissance négatif. Avec un faible taux de dilution (0,06 J-1), la théorie de la culture en continu n'était pas vérifiée. Ce taux critique de dilution se caractérisait par un contenu cellulaire en chlorophylle a faible et peut dépendre du mode de nutrition.
    Preview · Article · Sep 1997 · Annales de Limnologie - International Journal of Limnology
  • Lajos Vörös · Katalin V.- Balogh · Sándor Herodek
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    ABSTRACT: Seasonal variations of phyto-, bacterio- and colourless flagellate plankton were followed across a year in the large shallow Lake Balaton (Hungary). Yearly average chlorophyll-a concentration was 11 g 1–1, while the corresponding values of bacterioplankton and heterotrophic nanoflagellate (HNF) plankton biomass (fresh weight) were 0.24 mg 1–1 and 0.35 mg 1–1, respectively. About half of planktonic primary production was channelled through bacterioplankton on the yearly basis. However, there was no significant correlation between phytoplankton biomass and bacterial abundance. Bacterial specific growth rates were in the range of 0.009 and 0.09 h–1, and ended to follow the seasonal changes in water temperature. In some periods of the year, predator-prey relationships between the HNF and bacterial abundance were obvious. The estimated HNF grazing on bacteria varied between 3% and 227% of the daily bacterial production. On an annual basis, 87% of bacterial cell production was grazed by HNF plankton.
    No preview · Article · Oct 1996 · Hydrobiologia
  • M. Présing · S. Herodek · L. Vörös · I. Kóbor
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    ABSTRACT: N2-fixation and 15N-labelled ammonium and nitrate uptake were measured during a bloom of C. raciborskii in two basins of Lake Balaton. In the eastern basin when the chlorophyll-a content reached 70 μg/l the N2- fixation was low (59 mg N m-2 day-1) and the N uptake was dominated by ammonium (393 mg N m-2 day-1). The nitrate uptake was of minor importance in both basins (43 and 55 mg N m-1 day-1, respectively). In the western basin, the chlorophyll-a tentent was 160μg/l and recirculation of regenerated forms of nitrogen could not support the demand. Although the ammonium uptake was high (357 mg N m-2 day-1), the fixed nitrogen (407 mg Nm-2 day-1) exceeded it. The daily integrated carbon and nitrogen uptake ratios were 5.2 (weight/weight) in both basins.
    No preview · Article · Jan 1996 · Archiv fur Hydrobiologie
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    ABSTRACT: A pico sized Synechococcus species isolated from Lake Balaton was studied in batch and continuous cultures. This picocyanobacterium had a pH optimum at 8.5 and a temperature optimum at 28-30°C. The Ik value for growth was 52 μEinstein m−2 S−1, the maximum growth rate 2.27 d−1, the half saturation Constant of growth 1.2 μg PO4-P I−1 and the minimal cell quota 1.74 nig P g dry weight−1. The dry weight of cells showed a minimum, the chlorophyll-a/biomass ratio a maximum as a function of growth rate. Above the quota of 3.4 fg P Cell−1 significant amounts of non-reactive dissolved Phosphorous were released.
    No preview · Article · Jan 1996 · Internationale Revue der gesamten Hydrobiologie und Hydrographie
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    VERA ISTVÁNOVICS · SÁNDOR HERODEK
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    ABSTRACT: P-uptake kinetics of extremely P-deficient planktonic microorganisms were analyzed in shallow Lake Balaton by means of a conceptual model of P uptake. According to the model, net P uptake is a linear function of the driving force of the uptake and ceases below a substrate threshold for energetic reasons. We estimated net P-uptake and P-leakage rates from 32P-uptake data. The study period (January-May 1992) covered development, steady state growth, and collapse of a typical spring diatom bloom. 32P incorporation of 12-pm microorganisms was separated by postfiltration. On five occasions, net P-uptake rates were simultaneously obtained from chemical measurements. Chemically measured net P-uptake curves, 32P-uptake curves, and size partitioning of 32P incorporation can be recalculated from the constants of the linear force-flow model. The initial orthophosphate concentration fluctuated around 0.1 pg P liter-l. The community-average P threshold exceeded the initial P concentration by a mean factor of 1.4, that of the > 12-pm microorganisms by a mean factor of 3.9. Small-scale fluctuations of in situ P concentrations were necessary to maintain P uptake and growth of larger microorganisms. In a nonhomogeneous environment, sensitivity to the fluctuating nutrient concen- trations, efficiency of leakage reduction, and lower maintenance cell quotas may provide a competitive advantage to more complex-organisms.
    Preview · Article · Jan 1995 · Limnology and Oceanography
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    Istvánovics V · Herodek S · Szilágyi F · Pomogyi P

    Full-text · Conference Paper · Sep 1990
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    Full-text · Chapter · Jan 1990
  • Sándor Herodek · István Tátrai · János Oláh · L VOROS
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    ABSTRACT: Feeding experiments were carried out with fry of silver carp fed on cultured algae, Scenedesmus ellipsoideus, Anacystis nidulans, Anabaena flos-aquae, and on phytoplankton collected in Lake Balaton. Analyses of the intestinal contents of silver carp showed that blue-green algae and diatoms were ingested and digested to the greatest extent. Colonies of blue-greens and big forms of greens were ingested, but poorly digested. Fish were not able to ingest algae smaller than 10 μm in size. Silver carp fed on blue-greens consumed 11–13% of their body weight (wet wt) in a 40 mg l−1 algal suspension. Filtration rate, at the same food density, ranged between 2.6 and 3.3 l g−1 (body weight) 4 h−1. Algae labeled with 14C passed through the alimentary canals in an average time of 3.2 h. Feeding of silver carp was most intense in the afternoon and lowest at night. Fecal algae (Scenedesmus) did not increase either the biomass or the primary production at a fecal concentration of 1 mg l−1. At a fecal concentration of 3 mg l−1, however, there was a slight increase in both the biomass and the primary produciton. At 10 mg l−1 fecal concentration the biomass and primary production of living cells almost doubled. Fecal algae (Anabaena) increased the primary production at 10 mg l−1, but at 50 mg l−1 the biomass was three times and the primary production four times higher as compared with the control.
    No preview · Article · Dec 1989 · Aquaculture
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    Vera Istvánovics · Sándor Herodek · Ferenc Szilágyi
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    ABSTRACT: Adsorption of phosphate by sediments could be described by the Langmuir isotherm. The adsorption capacity of the sediments increased with their NaOH-extractable iron content, and the energy of adsorption was proportional to their calcite content.Increasing phosphate saturation of the sediments could be demonstrated near the inlet of the Zala River into the Kis-Balaton reservoir, as a result of high external loading. Phosphate saturation of the sediments remained similar in the hypertrophic and mesotrophic basins of Lake Balaton. This was explained by the continuous renewal of calcite, the main phosphate sorbent in this calcareous lake.A comparison of the interstitial SRP concentration and the adsorption/desorption concentration limit, derived from the Langmuir isotherm, indicated that sorption is of major importance in regulation of the interstitial phosphate concentration.In Lake Balaton desorption occurs whenever the sediments are resuspended; adsorption takes place only in the sediments. In the two reservoirs, adsorption and biotic uptake are equally important in the removal of phosphorus from the water, depending on the actual loading and primary production.
    Full-text · Article · Nov 1989 · Water Research
  • Tibor Kutas · Sándor Herodek
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    ABSTRACT: The process of eutrophication has threatened the viability for recreation of the largest lake in Middle Europe, Lake Balaton. For studying and simulating the system a deterministic model (a system of differential equations) has been constructed. The four basins of the lake are described by the same model and the models of basins are concatenated by hydrological throughflow. The one-basin model with its ten state variables describes the main mass transport processes in the pelagic zone of the lake and in the sediment, as the lake is shallow. The model can simulate seasonal changes and it is able to forecast the effect of some measures on water quality in the short term. The simulation runs show that the measures can be effective when the phosphorus-removing water-dam systems involved in tertiary treatment of sewage water work at a high rate.
    No preview · Article · Nov 1987 · Ecological Modelling
  • Sándor Herodek · Vera Istvánovics
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    ABSTRACT: Sediment phosporus was studied by a combination of the fractionation procedure of Hieltjes & Lijklema and the isotopic dilution technique in a mesotrophic (Tihany) and a hypertrophic (Keszthely) basin of Lake Balaton. In the calcareous sediments the largest part of phosphorus was bound to calcium. Iron-bound and residual P showed higher concentrations at Keszthely than at Tihany. There was little loosely adsorbed P at both locations. Vertical differences in P fractions of the sediments were more pronounced at Keszthely than at Tihany. Exchangeability of the fractions decreased in the following sequence: iron-bound > loosely adsorbed > calcium-bound > residual. Phosphorus, particularly in the calcium-bound fraction, was more mobile at Keszthely, and its exchangeability decreased rapidly downwards at both stations. Four times more potentially mobile phosphorus has been accumulated by the upper sediment layer at Keszthely than at Tihany.
    No preview · Article · Mar 1986 · Hydrobiologia