Edit Ágoston-Szabó

Influence of water level fluctuation on the spatial dynamic of the water chemistry at Lake Fertõ/Neusiedler See

Abstract Lake Ferto/Neusiedler See is a steppe lake situated on the Hungarian-Austrian border with a surface area of 309 km 2 . It is an extremely shallow lake with regulated outflow. 54% of the whole lake and 85% of the Hungarian part (75 km 2 ) is covered by reed. There are numerous reedless areas (inner ponds) of variable size within the reed belt, which is enmeshed with canals connecting the inner ponds with the open water areas. Fundamental differences were recorded in the water chemistry of the three water type areas, open water, canals and inner ponds. The degree of these differences is basically determined by the distance from the open water areas and the water level of the actual years. An extremely high, an average and an extremely low water level year was examined, in order to present the spatial and temporal differences in the water chemistry of the investigated water bodies. Differences due to the water level fluctuation between years in the three different water types are discussed on the basis of electrical conductivity, cation, and anion concentration changes of the water. Our results support the concept of high instability of Lake Ferto and describe habitats with remarkable temporal and spatial variability. The high influence of water level on habitat conditions at different sites of the lake recommend a carefull water level regulation strategy.

Decomposition of Typha angustifolia and Phragmites australis in the littoral zone of a shallow lake

Decomposition of air-dried live Typha angustifolia (L) stems and leaves and Phragmites australis (Cav. Trin ex Steud.) leaves and culms were studied in a shallow freshwater lake (Lake Fehér, Fertő-Hanság National Park, Hungary) using the litter bag technique. Samples were analyzed for dry mass, fiber (cellulose, hemicelluloses, lignin) and nutrient (C, N, P, S) contents, litter-associated fungal biomass (ergosterol concentration), potential microbial respiration (electron transport activity: ETS) and cellulolytic bacteria. In terms of mesh size, there were no significant differences in the examined parameters of P. australis leaves and culms and T. angustifolia stems with leaves. P. australis leaves had the highest rate of decomposition and P. australis culms the lowest. Hemicellulose degraded more rapidly than the other fibers, while the lignin had the slowest rate of decomposition.The ETS activity of the examined plant litter types increased from day 91st to 237th while decomposition processes were most active, ergosterol contents were high, and there were few cellulolytic bacteria. The counts of cellulolytic bacteria fluctuated during the decomposition period, they were high at the beginning then they decreased. In each case bacteria were found to be the first colonizers of plant detritus, and were followed by fungal growth.

Comparison between biomass and C, N, P, S contents of vigorous and die-back reed stands of Lake Fertő/Neusiedler See

The production of vigorous and die-back sites of the same reed belt and nutrient content of reed were studied to detect possible causes of reed die-back. Shoot density, total aboveground and belowground biomass and their C, N, P and S contents were also determined.Samples were collected from three vigorous and three die-back sites of Lake Fertő/Neusiedler See in 1996 and 1997. Reed stands were compared when the biomass was maximal in both years. Reed shoots were significantly (p = 5%) shorter, thinner and had less internodes at the die-back sites than at the vigorous sites, where the aboveground biomass was 1.5–2.0 times and the leaf area index (LAI) 1.7–2.5 times higher. The belowground biomass was nearly the same at the vigorous and die-back sites. The amount of decaying belowground biomass was less than 50% of the total belowground biomass at the vigorous sites, while it reached 75% at the die-back sites.Different N, C, P and S concentrations were found in the reed organs studied (leaves, culm, rhizome and roots). The N concentration in leaves, culm and rhizome was higher at the die-back sites, where the P concentration was the lowest. There were no significant differences in the S concentration of the examined reed organs as comparing the vigorous and degraded reeds. The C concentration of culms were higher, while that of the living rhizomes were lower at healthy than at the die-back sites. The N, P, C and S standing stocks in the aboveground biomass were significantly lower at the die-back sites than at the vigorous sites. In the belowground biomass the P standing stock was significantly lower, while the N standing stock was significantly higher at the die-back sites than at the vigorous sites.Not more than 17% of the total dry mass m−2, 17% of the C, 24% of the N, 14% of the S and 27% of the P standing stock was found in the aboveground phytomass produced in the actual year.

Reed Stand Conditions at Selected Wetlands in Slovenia and Hungary

We determined the characteristics of reed stands at an intermittent lake in Slovenia and degraded and vital reed stands in Hungary. The disturbance in reed performance was measured through growth analysis, amino acid analysis in basal culm internodes, and photochemical efficiency of photosystem II (PSII) in leaves. Morphological parameters indicated higher disturbance in the development of degraded and intermittent reed stands in comparison to vital reed stands. Similarly, total free amino acid contents in basal culm internodes reflected temporary stress response in degraded and intermittent reed stands. On the other hand, potential photochemical efficiency showed undisturbed energy harvesting of all reed stands, even though actual photochemical efficiency revealed temporary disturbance of PSII. The most unfavourable condition for reed development seems to be degraded reed stand of Kis-Balaton wetland and littoral reed stand of intermittent Lake Cerknica.

Effects of the introduction of pre-treated wastewater in a shallow lake reed stand

Abstract Reed stands may be employed in the amelioration of water quality or even in the treatment of wastewater. In this study, the nutrient concentrations of (i) the above- and below-ground Common Reed (Phragmites australis) biomass, and (ii) surface and interstitial water were analyzed in a natural stand used in wastewater treatment. The reed stand was located in Hungarian part of Lake Fertő/Neusiedler See, by the shore near Fertőrákos Bay. The nitrate, phosphate and dissolved organic nitrogen concentrations of surface water were found to be higher on the inlet side of the reed stand compared to the outlet. The N and P concentrations in the above-ground biomass and P concentrations in the below-ground biomass increased after the introduction of pre-treated wastewater. The inter-annual differences in the characteristics of sediment interstitial water and in the nutrient content of reed tissues were assessed using statistical methods. The samples taken before and after the introduction of the pre-treated wastewater in the parcel formed different clusters. The results of the study provide further evidence that the nutrient retention capacity of natural stands of P. australis may be employed in the treatment of wastewater while protecting and preserving the valuable natural assets of the lake.

Limnological characteristics of a Danube oxbow-lake (Danube-Dráva National Park, Hungary)

Spatial and temporal changes in the water chemical parameters and chlorophyll-a concentration were investigated in Kulső-Beda oxbow-lake of the Danube and compared with that of the main channel in 2007-2008. The oxbow-lake water differed from that of the main arm with regards to concentrations of the C, N and P forms. The NO3 - -N, PO4 3- -P, TDN, TDP concentrations were remarkably lower, while the concentrations of DOC, TDC, TOC and of chlorophyll-a were higher in the oxbow-lake than in the main channel. The differences between the NO3 - -N and PO4 3- -P concentrations of the main arm and oxbow-lake decreased with increasing river discharge. The phytoplankton biomass signifi cantly correlated with the TP (r=0.90), NO3 - -N (r=-0.45) concentrations and TDN:TDP ratio (r=-0.47), NO3 - -N:PO4 3- -P ratio (r=-0.55), which suggested P limitation of phytoplankton growth. Signifi cant positive correlation was found between the chlorophyll-a and SPM, POC. The phytoplankton biomass negatively, while NO3 - -N concentration positively correlated with the water discharge of the main arm. The limno- logical characteristics of BDU were dependent on the water regime of the main channel.

Trophic Status and Phytoplankton Limitation Conditions in a Few Bulgarian and Hungarian Danube River Wetlands

Abstract The phytoplankton limitation conditions in a few Bulgarian and Hungarian wetlands and in two more sampling sites, one for each Danube stretch, were investigated by means of trophic state index of Carlson (1977) for phytoplankton chlorophyll-a (CHL), Secchi disk depths (SD), total phosphorus (TP), and total nitrogen (TN) concentrations. Phytoplankton of both river sites was not limited by non-algal turbidity, nor was they phosphorus and nitrogen limited. In summer months the studied wetlands were predominantly nitrogen limited, while in spring and autumn limitation by non-algal turbidity prevailed.

Bacterioplankton from Two Hungarian Danube River Wetlands (Beda-Karapancsa, Danube-Drava National Park) and its Relations to Environmental Variables

Abstract Seasonal and spatial distribution of bacterioplankton from two Hungarian oxbow lake type wetlands, Mocskos-Danube and Riha, was studied. They were both covered by macrophytes and they had different hydrological connectivity to the Danube. The six sampling campaigns from April to October 2014 included parallel samples from the Danube River at Mohács, Hungary. Bacterial abundance was the highest in spring and in Mocskos-Danube, followed by Mohács and Riha. Positive relationships existed between bacterioplankton and temperature on one hand and suspended solids, pH, PO4-P and chl-a on the other. Negative correlations were with DOC, dissolved oxygen and NH4-N.

Chemical Properties of the Sediment Interstitial Water at Lake Fertő/Neusiedler See

The chemical parameters of the surface and sediment interstitial water from the 0–20 and 20–40 cm sediment layer were investigated in different reed stands of Lake Fertő/Neusiedler See. The temperature, pH, redox potential, \({\textrm{SO}}_4 ^{2 - }\), \({\textrm{NO}}_2 ^-{\textrm{-N}}\) and \({\textrm{NO}}_3 ^ -{\textrm{-N}}\) concentrations decreased, while the electrical conductivity and the concentrations of \({\textrm{Na}}^{{+}} ,{\textrm{Ca}}^{2 + } ,{\textrm{K}}^ + ,{\textrm{Mg}}^{2 + } ,{\textrm{Cl}}^ - ,{\textrm{PO}}_4 ^{3 -}{\textrm{-P}}\) and \({\textrm{S}}^{2 - }\) increased in the function of sediment depth. As comparing the vegetated and unvegetated areas of the sampling sites: \({\textrm{PO}}_{\textrm{4}} ^{3-}{\textrm{-P}},\;{\textrm{S}}^{2-}\) and \({\textrm{NO}}_2 ^-{\textrm{-N}}\) concentrations of the interstitial water were lower and the \({\textrm{SO}}_4 ^{2- }\) and \({\textrm{NO}}_3 ^ -{\textrm{-N}}\) concentrations were higher at vegetated areas, which demonstrated the effect of internal oxygen transport of the Phragmies australis rhizosphere on the chemical characteristics of interstitial water. The degraded reed stand was characterised by low redox potential and high \({\textrm{S}}^{2 - }\) concentrations. The trace element concentrations of the surface water decreased in the order \({\textrm{B}}^{3 + } > {\textrm{Fe}}^{2 + } > {\textrm{Al}}^{3 + } > {\textrm{Pb}}^{2 + } > {\textrm{Zn}}^{2 + } > {\textrm{Mn}}^{2 + }\) and increased with the depth of the sediment; their concentrations were higher in the sediment interstitial water of unvegetated than of the vegetated areas.

Decomposition of Typha angustifolia (L.) in a shallow lake

In wetland eeosystems a eonsiderable part o f the organic material produetion is formed by emergent maerophytes, whieh play an important part in the detritus food ehain (WETZEL 1981 ). Litter decay i s an important component ofthe nutrient eycling process, and the investigation o f its deeomposition is an important aspeet o f the analysis o f ecosystem function. The aim of this study was to evaluate the decomposition dynamics of Typha angustifolia (L.). ehanges in dry mass remaining, mierobial activity (based on the eleetron transport aetivity: ETS), number of cellulolitic bacteria, fungal biomass ( ergosterol coneentrations) were studied during decomposition.