Társadalmi konfliktusokat generáló ökológiai történések a Balaton életében az utóbbi néhány évtizedben – A víz barna elszíneződése

Ecological Developments of the Recent Decades Generating Social Conflicts in the Life of the Lake Balaton – Brown Discoloration of Water The largest quantities of brown coloured dissolved organic substances get into Lake Balaton in the Keszthely-basin through the River Zala and on the south shore from Nagyberek (peat bog) through pumping. Tourists avoid the beaches with brown water despite the fact that it does not pose any danger. Even though the humic substances causing the brown colour are not harmful for bathers, these compounds, however, do influence ecological processes. Humic substances are natural substances which are the decomposition products of dead plants. Their water-soluble fractions are fulvic acids and humic acids, while their third fraction (humin) is not water soluble. Humic substances play multiple ecological roles in surface waters: they serve as a carbon source for bacteria; change the underwater light climate through the increased attenuation of the short-wavelength ultraviolet (UV) radiation of the Sun; their photodegradation produces toxic free radicals containing oxygen (which is transformed to hydrogen peroxide); and they change the behaviour of other substances through their complex-forming property. A significant increase in the chromophoric dissolved organic matter load of the Lake can be anticipated because of the planned extension of the currently flooding area (16 km2) by the lower Kis-Balaton reservoir up to 52 km2.Ecological Developments of the Recent Decades Generating Social Conflicts in the Life of the Lake Balaton – Brown Discoloration of Water The largest quantities of brown coloured dissolved organic substances get into Lake Balaton in the Keszthely-basin through the River Zala and on the south shore from Nagyberek (peat bog) through pumping. Tourists avoid the beaches with brown water despite the fact that it does not pose any danger. Even though the humic substances causing the brown colour are not harmful for bathers, these compounds, however, do influence ecological processes. Humic substances are natural substances which are the decomposition products of dead plants. Their water-soluble fractions are fulvic acids and humic acids, while their third fraction (humin) is not water soluble. Humic substances play multiple ecological roles in surface waters: they serve as a carbon source for bacteria; change the underwater light climate through the increased attenuation of the short-wavelength ultraviolet (UV) radiation of the Sun; their photodegradation produces toxic free radicals containing oxygen (which is transformed to hydrogen peroxide); and they change the behaviour of other substances through their complex-forming property. A significant increase in the chromophoric dissolved organic matter load of the Lake can be anticipated because of the planned extension of the currently flooding area (16 km2) by the lower Kis-Balaton reservoir up to 52 km2

Az ultraibolya sugárzás szerepe tavak oldott szervesanyagainak transzformációjában és degradációjában = Role of ultraviolet radiation in the transformation and degradation of dissolved organic substances in lakes

Sekély tavakra (30 magyarországi víztest, 140 mérés) ultraibolya (UV) és látható (PAR) hullámhossz tartományban többváltozós regressziós modelleket fejlesztettünk ki a fényabszorpciós komponensek: algák, algamentes lebegőanyagok, színes oldott szervesanyagok (CDOM) és a vertikális extinkciós koefficiensek (Kd) közötti összefüggés leírására. A modellek megadták az egyes komponensek specifikus Kd értékeit. Ezek, és a komponensek koncentráció értékei alapján vízalatti mérésre alkalmas radiométer hiányában in situ fénymérés nélkül kiszámíthatóak egy adott víztestre jellemző Kd értékek. A vizsgált tavakban a CDOM határozta meg a vízalatti UV klímát, az algák szerepe alárendelt volt. A PAR klímát a legtöbb víztestben a lebegőanyagok határozták meg, de hipertróf vizekben az algák, míg barna vizekben a CDOM volt a meghatározó. Kísérletesen megállapítottuk, hogy az UV sugárzás hatására az oldott szervesanyagok bomlottak, az oldott szervesszén (DOC) koncentrációja csökkent, a hidrogénperoxidé nőtt, miközben a szervesanyagok kémiai és fizikai tulajdonságai változtak, így barna színük fakult, fényabszorpciójuk és fluoreszcencia intenzitásuk csökkent, miközben a biológiailag hozzáférhető DOC koncentráció többszörösére nőtt. Kimutattuk, hogy az UV sugárzás hatása a bakterioplanktonra komplex, direkt gátló és indirekt gátló és serkentő hatás egyaránt érvényesült. A mikrobiális élőlényegyüttesek működése és a vízi szénforgalom megértése a CDOM fotolízisének ismerete nélkül nem lehetséges. | Multiple regression models were developed in the ultraviolet (UV) and visible (PAR) wavelength range to describe the relationship between light-absorbing components: algae, algal-free suspended solids, coloured dissolved organic matter (CDOM) and vertical attenuation coefficients (Kd) in shallow lakes (30 Hungarian water bodies, 140 measurements). The models have provided the specific Kd values of the components. Based on these and the concentration of the components, the Kd can be calculated without in situ measurement in the absence of an underwater radiometer. The underwater UV climate was mainly determined by CDOM in the studied lakes, the role of algae was negligible. The PAR climate was determined by suspended solids in most cases, but in hypertrophic waters the algae and in brown colour waters the CDOM was dominant. We have experimentally ascertained that the dissolved organic substances were decomposed by UV radiation: the DOC decreased, the H2O2 increased, while their brown colour faded, their absorbance and fluorescence intensity decreased, while the concentration of the biologically available DOC multiplied. We have found that the effect of UV radiation on bacterioplankton is complex: both the direct inhibitory and indirect inhibitory and stimulating effects were detected. Our research shows that the understanding of the functioning of microbial assemblages and the aquatic carbon cycle is not possible without the thorough knowledge of the photolysis of CDOM

A fitoplankton produktivitása és diverzitása pikoplankton dominanciájú vízterekben = Productivity and diversity of phytoplankton in picoplankton dominated water bodies

Feltártuk a bakteriális méretű algákban (pikoplankton) gazdag turbid vizekben a pikoplankton tömegének, összetételének, dinamikájának és fotoszintézisének alapvető jellemzőit. A fitoplankton tömege alapján ezek a tavak hipertrófok (a-klorofill>100 micro g/l), ugyanakkor a fénylimitáció miatt elsődleges termelésük a vártnál alacsonyabb volt. Vizükben a pikoplankton abundanciája egy-két nagyságrenddel nagyobb volt, mint más tavakban, télen a pikoeukarióták nyáron a pikocianobaktériumok domináltak a Balatonhoz hasonlóan. A Balatonban a pikoalgák részesedése az összes produkcióból 23-54% között volt. Megállapítottuk, hogy a pikoplankton abundancia folyó vizekben egy nagyságrenddel kisebb, mint tavakban, azonos fitoplankton biomassza esetén. A Balatonból egy új pikoeukarióta, a szikes tavakból egy új pikocianobaktérium morfotaxont írtunk le. A természetes pikoplankton együttesek molekuláris vizsgálata bizonyította, hogy a Pannon Biogeográfiai Régió víztereinek Synechococcus flórája igen gazdag és diverz. Az izolált pikocianobaktérium törzsek genetikai karakterizálása is ezt az eredményt támasztotta alá. A Böddi-székből izolált törzsek a pikofitoplankton klád egy új, eddig tenyésztésbe nem vont csoportját képviselik. Pikoeukarióta és pikocianobaktérium törzsek ökofiziológiai vizsgálatával bizonyítottuk, hogy a Duna-Tisza közi szikes tavakban (és minden bizonnyal más tavakban is) a fény és a hőmérséklet változása együtt szabályozza a pikoalgák szezonális szukcesszióját. | The abundance, composition, dynamics and photosynthesis of the bacterium-sized algae (picoplankton) has been studied in Hungarian turbid waters, where the abundance of picoplankton is one or two order of magnitude higher than in other lakes. Based on the phytoplankton biomass these ponds were hypertrophic (chlorophyll-a > 100 micro g/l), however the primary production was lower than expected due to light limitation. Picoeukaryotes dominate in winter, while picocyanobacteria dominate in summer, similarly to Lake Balaton, where the proportion of the picoplankton in the total primary production was 23 and 54%. It has been stated, that the picoplankton abundance in running waters was one order of magnitude lower, than in shallow lakes having the same trophic state. One new eukaryotic and one cyanobacterial picoalgal morphotaxa has been described. The molecular characterization of phytoplankton assemblages showed that the Synechococcus flora of the Pannon Biogeographic Region is very diverse. The molecular identification of isolated picocyanobacterial strains also confirmed these results. The picocyanobacterial strains isolated from Böddi-szék pond formed a new, distinct group inside the picophytoplankton clade. The ecophysiological studies of picoeukaryotic and picocyanobacterial strains showed that the light and temperature control together the seasonal succession of the picoplankton in turbid soda lakes in the Danube-Tisza Interfluve (and presumably in other shallow lakes)

Quasi-phase-matching high-harmonic radiation using chirped THz pulses

High-order harmonic generation in the presence of a chirped THz pulse is investigated numerically with a complete 3D nonadiabatic model. The assisting THz pulse illuminates the high-order harmonic generation gas cell laterally inducing quasi-phase-matching. We demonstrate that it is possible to compensate the phase mismatch during propagation and extend the macroscopic cutoff of a propagated strong IR pulse to the single-dipole cutoff. We obtain 2 orders of magnitude increase in the harmonic efficiency of cutoff harmonics (170 eV) using a THz pulse of constant wavelength, and a further factor of 3 enhancement when a chirped THz pulse is use

Társadalmi konfliktusokat generáló ökológiai történések a Balaton életében az utóbbi néhány évtizedben - A vízszintváltozás hatása a parti öv növényvilágára | Social Conflict Generating Ecological Developments in the Life of Lake Balaton in Recent Decades – Effect of water level fluctuation on the plants of the littoral zone

While the Hungarian public was primarily concerned with the water quality of Lake Balaton in the 1980s and 1990s, low water levels and their environmental effects became the focus of public attention in 2002, 2003 as well as 2012. Accurate and reliable monthly and yearly data about the water balance of Lake Balaton has been available since 1921. The amounts of water getting into the lake from the catchment area have been considerably less than average in nine percent of the period between 2001 and 2012; the water in the catchment area became scarce and the water levels of the lake notably decreased during the drier than average years of 2001-2004 and 2012. Cladophora glomerata (filamentous green alga) appeared in large quantities in the shallow waters of the south shore in the summer of 2002, 2003 as well as 2012. It is not a new phenomenon: the first documented Cladophora explosion in Lake Bala-ton was in 1934. Scientists at the Balaton Limnological Institute (Center for Ecologi-cal Research of the Hungarian Academy of Sciences) studied the Cladophora vegetation of the south shore in July 2003. They found that excessive Cladophora growth—harming tourism with its gooey green mats and rotting muck—appeared where the water depth was lower than 30 cm. This explosion, however, is not a consequence of water pollution but an unavoidable consequence of the low water levels. The results show that the photosynthetical apparatus of the main submerged macrophyte species have adapted to the semi-dark waters of Lake Balaton. The photosynthetical parameters of submerged macrophytes indicate that they can survive and disperse in parts of the lake where the water is no deeper than 2.2-2.3 m. It means that the area suitable for the establishment of submerged macrophytes increases by 60 percent with a 50 cm decrease in the water levels, while a 100 cm decrease means a threefold increase in the size of the area favourable for submerged macrophytes. The decrease in water levels contribute considerably to the spread of reed. This is due the increase in drier areas suitable for sexual reproduction on the one hand and to the oxidation of sediment on the other. The emerging of a reed-covered area out of the water—even if for a short period—contributes considerably to the prevention of reed decline. The artificial stabilization of the water levels in the past fifty years has greatly contributed to the slow degradation of the flora in the littoral zone. At the same time, the low water levels of the past decade have shown that low water levels do not damage the macrophyte populations of Lake Balaton

Genetic optimization of attosecond-pulse generation in light-field synthesizers

We demonstrate control over attosecond pulse generation and shaping by numerically optimizing the synthesis of few-cycle to sub-cycle driver waveforms. The optical waveform synthesis takes place in an ultrabroad spectral band covering the ultraviolet-infrared domain. These optimized driver waves are used for ultrashort single and double attosecond pulse production (with tunable separation) revealing the potentials of the light wave synthesizer device demonstrated by Wirth et al. [Science 334, 195 (2011)]. The results are also analyzed with respect to attosecond pulse propagation phenomena

Unusual behaviour of phototrophic picoplankton in turbid waters

Autotrophic picoplankton (APP) abundance and contribution to phytoplankton biomass was studied in Hungarian shallow lakes to test the effect of inorganic turbidity determining the size distribution of the phytoplankton. The studied lakes displayed wide turbidity (TSS: 4–2250 mg l-1) and phytoplankton biomass (chlorophyll a: 1–460 μg l-1) range, as well as APP abundance (0 and 100 million cells ml-1) and contribution (0–100%) to total phytoplankton biomass. Inorganic turbidity had a significant effect on the abundance and contribution of APP, resulting in higher values compared to other freshwater lakes with the same phytoplankton biomass. Our analysis has provided empirical evidence for a switching point (50 mg l-1 inorganic turbidity), above which turbidity is the key factor causing APP predominance regardless of phytoplankton biomass in shallow turbid lakes. Our results have shown that turbid shallow lakes are unique waters, where the formerly and widely accepted model (decreasing APP contribution with increasing phytoplankton biomass) is not applicable. We hypothesize that this unusual behaviour of APP in turbid waters is a result of either diminished underwater light intensity or a reduced grazing pressure due to high inorganic turbidity