[Show abstract][Hide abstract] 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.
Annales de Limnologie - International Journal of Limnology 01/2011; 47:141-150. · 0.74 Impact Factor
[Show abstract][Hide abstract] 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.
Internationale Revue der gesamten Hydrobiologie und Hydrographie 11/2010; 81(4):503 - 512.
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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.
Annales de Limnologie - International Journal of Limnology 11/1997; 33(04):223 - 233. · 0.74 Impact Factor
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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.
Limnology and Oceanography - LIMNOL OCEANOGR. 01/1995; 40(1):17-32.
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] ABSTRACT: Seasonal orthophosphate uptake of natural plankton has been studied in hypertrophic and mesotrophic basins of Lake Balaton. Initial uptake of carrier-free labelled phosphoric acid followed first order kinetics in accordance with a single two-compartment model. In isotope equilibrium from 1.2 to 9.7 per cent of radioactivity was found in the filtrate. Turnover times of orthophosphate in water were some minutes in summer and two orders of magnitude longer in winter and April. Turnover time of phosphorus in microorganisms has been estimated on the basis of equilibrium isotope distribution between water and particular phases and turnover time in water. It ranged from 28 to over 1 000 min. The shortest times were found in summer, and the longest in winter. Turnover time of orthophosphate in water increased in relation to phosphate additions according to Michaelis-Menten kinetics. The values of Michaelis-constant plus the ambient orthophosphate concentration (K + Sn) suggested an overestimation of real phosphate concentrations by chemical measurements, being much lower than soluble reactive phosphorus contents in most cases, as it is well-known in many other lakes. Both K + Sn values and maximum uptake velocities (V) were significantly higher in the hypertrophic basin than in the mesotrophic one, in contrast to essentially similar values of turnover times. Maximum uptake velocity per unit chlorophyll-a P opt:V ratio showed extreme to moderate phosphorus deficiency for Lake Balaton plankton, which seemed to decrease somewhat in the course of eutrophication.