Viktor R. Tóth

• PhD
• Senior Researcher at Balaton Limnological Research Institute

Lake Balaton, a large shallow freshwater lake in Hungary, exhibits diverse bacterioplankton communities influenced by various environmental factors. This study aims to evaluate the bacterial diversity in Lake Balaton using the long-read approach to 16 S rRNA gene sequencing. Water samples were collected from a wide network of 33 locations across th...

Common reed (Phragmites australis) is a cosmopolitan species, though its dieback is a worldwide phenomenon. In order to assess the evolutionary role of phenotypic plasticity in a successful plant, the values and plasticity of photophysiological traits of Phragmites australis were investigated in the Lake Fertő wetlands at 5 sites with different deg...

The biological synchrony of neighbouring lakes in Central Europe was evaluated by analysing the concurrent time series of algal biomass variables using long-term (1999–2019) satellite (Landsat 7) derived chlorophyll-index data. The synchrony between the hydrologically connected and disconnected lakes was estimated and compared. Although the hydrolo...

Telonemia are one of the oldest identified marine protists that for most part of their history have been recognized as a distinct incertae sedis lineage. Today, their evolutionary proximity to the SAR supergroup (Stramenopiles, Alveolates, and Rhizaria) is firmly established. However, their ecological distribution and importance as a natural predat...

A multidisciplinary approach demonstrates how submerged macrophytes generate high phenological variability in Hungary's Lake Balaton. A 239‐month time series of water chlorophyll indices derived from Landsat 7 imagery from 1999 to 2019 was used. These data facilitated the generation of area‐based phenological patterns, which allowed an assessment o...

The influence of macrophytes on the optical environment of the littoral zone was assessed by studying the effect of monospecific Potamogeton perfoliatus on the quantitative and qualitative properties of light and the response of plants to this altered environment. P. perfoliatus was shown to alter the optical environment and consequently its own ar...

Lake Balaton, a shallow polymictic freshwater lake in Central Europe, became eutrophic in the 1970s. To retain the inorganic nutrients from the main tributary River Zala, a semi-artificial system called the Kis-Balaton Water Protection System (KBWPS) was constructed in the early 1980s. In 2015, the system was reconstructed and modernised, thus offe...

Conflicts and natural disasters affect entire populations of the countries involved and, in addition to the thousands of lives destroyed, have a substantial negative impact on the scientific advances these countries provide. The unprovoked invasion of Ukraine by Russia, the devastating earthquake in Turkey and Syria, and the ongoing conflicts in th...

Background Macrophytes are key players in aquatic ecosystems diversity, but knowledge on variability of their functional traits, among and within species, is still limited. Remote sensing is a high-throughput, feasible option for characterizing plant traits at different scales, provided that reliable spectroscopy models are calibrated with congruou...

Photomorphogenesis is a process by which photosynthetic organisms perceive external light parameters, including light quality (color), and adjust cellular metabolism, growth rates and other parameters, in order to survive in a changing light environment. In this study we comprehensively explored the light color acclimation of Cyanobium gracile, a c...

Growth of submerged and emergent macrophytes was studied together with heterotrophic bacterioplankton abundance and production in two Hungarian shallow lakes with dominant macrophyte covers. It was expected that bacterioplankton numbers and activity would have an effect on macrophyte biomass accumulation. Bacterial production and abundance showed a...

Macrophytes are key players in aquatic ecosystems diversity, but knowledge on variability of their functional traits, among and within species, is still limited. Remote sensing is a high-throughput, feasible option for characterizing plant traits at different scales, provided that reliable spectroscopy models are calibrated with congruous empirical...

Remote sensing of vegetation has largely been revolving around the measurement of passive or active electromagnetic radiation of the top of the canopy. Nevertheless, plants hold a vertical structure and different processes and intensities take place within a plant organism depending on the environmental conditions. One of the main inputs for photos...

The relationship between invasive plant functional traits and their invasiveness is still the subject of scientific investigation, and the backgrounds of transition from non-native to invasive species in ecosystems are therefore poorly understood. Furthermore, our current knowledge on species invasiveness is heavily biased toward terrestrial specie...

Complex aquatic environments, such as coastal and inland waters have been experiencing deterioration in water quality due to increased anthropogenic impact and climate change. There is an increased demand to have reliable, fast and continuously available techniques to monitor these waters. Advances in remote sensing technology provides the possibil...

The relationship between invasive plant functional traits and their invasiveness is still the subject of scientific investigation, and the backgrounds of transition from non-native to invasive species in ecosystems are therefore poorly understood. Furthermore, our current knowledge on species invasiveness is heavily biased toward terrestrial specie...

The Ocean and Land Color Instrument (OLCI) onboard Sentinel 3A satellite was launched in February 2016. Level 2 (L2) products have been available for the public since July 2017. OLCI provides the possibility to monitor aquatic environments on 300 m spatial resolution on 9 spectral bands, which allows to retrieve detailed information about the water...

Under the current high anthropic pressure and climate change scenarios, a trend towards increasing changes in the trophic status of shallow lakes, and the development of opportunistic floating species is to be expected. This raises the need for monitoring and management actions to prevent widespread environmentally negative effects (e.g., anoxia)....

Littoral zones of freshwater lakes are exposed to environmental impacts from both terrestrial and aquatic sides, while substantial anthropogenic pressure also affects the high spatial, and temporal variability of the ecotone. In this study, the possibility of monitoring seasonal and spatial changes in reed (Phragmites australis) stands using an unm...

Eutrophication and enhanced external nutrient loading of lakes and seas are most clearly reflected by increased cyanobacterial blooms, which are often toxic. Freshwater cyanobacteria produce a number of bioactive secondary metabolites, some of which have allelopathic properties, significantly influencing the biological processes of other algae, the...

Earth observation has rapidly evolved into a state-of-the-art technology providing new capabilities and a wide variety of sensors; nevertheless, it is still a challenge for practitioners external to a specialized community of experts to select the appropriate sensor, define the imaging mode requirements, and select the optimal classifier or retriev...

Lakeshore vegetation, and in general wetlands, are a challenging case for mapping given the inherited complexity of the ecosystems they host and their associated dynamic temporal and spatial nature. Remote sensing has been traditionally a tool for vegetation related studies; however the applications and capabilities it offers are constrained by the...

Lakes are important features of the landscape and climate system, and trends and changes in their water quality have been identified as important to monitor within the context of the Water Framework Directive of the European Commission. Phytoplankton form the base of the aquatic food chain and productivity, and also have a major impact on water qua...

Macrophytes are important elements of freshwater ecosystems, fulfilling a pivotal role in biogeochemical cycles. The synoptic capabilities provided by remote sensing make it a powerful tool for monitoring aquatic vegetation characteristics and the functional status of shallow lake systems in which they occur. The latest generation of airborne and s...

This article is based on field measurements on the lake Balaton (Hungary) during the three days: 10, 11, and 12 September 2008. The expedition was performed with the aim to test recently developed ultraviolet (UV) fluorescent portable lidar UFL-8 in natural lake waters and to validate it by contact conventional measurements. We had opportunity to c...

Deteriorating environments in shallow waters place significant pressure on aquatic plants. To estimate the morphological and genetic diversity of submerged macrophytes at 5 sites characterized by varying degrees of human impact, Myriophyllum spicatum L. was studied. Sediment nitrogen concentrations were found to be significantly correlated with the...

The biomass and composition of autotrophic communities in the littoral zone are mainly affected by light availability. In a field study, the spectral attenuation of periphyton was assessed. Periphyton absorbed more light in the red than in the infrared spectral range, resulting in a lower red to infrared ratio (~0.3 during the most active period of...

Water level fluctuations play a vital role in regulating macrophytes of shallow lakes. Morphology and growth dynamics of Phragmites australis, together with physico-chemical parameters of the sediment, were studied at stable (not degrading) and die-back (degrading) sites of Lake Balaton over an 8-year period that included low and average water leve...

Life-history traits like dominance of certain reproductive modes (e.g. vegetative, specialized, unspecialized or sexual propagules) and overwintering strategies (evergreen or re-sprouting) determine the success and timing of the ability of aquatic plants to colonize new areas. In the present experiment the distribution of these reproductive modes w...

Monitoring of lakeshore ecosystems requires fine-scale information to account for the high biodiversity typically encountered in the land-water ecotone. Sentinel-2 is a satellite with high spatial and spectral resolution and improved revisiting frequency and is expected to have significant potential for habitat mapping and classification of complex...

This paper presents certain results of remote sensing of the seas and inland waters, obtained using a portable Laser Induced Fluorescence (LIF) LiDAR in the expeditions of the Shirshov Institute of Oceanology, Russian Academy of Sciences in recent years. The ultraviolet fluorescence lidars (UFL) portable series used in these studies were developed...

Since the beginning of the 1960s an escalating deterioration of reed beds in parts of Europe has been often observed. Hence, the ‘reed die-back’ as it was later named, has been a phenomenon of great scientific interest and concern to conservationists worldwide and intensively studied by field ecologists. Imaging spectroscopy has frequently been emp...

Phytoplankton biomass is important to monitor in lakes due to its influence on water quality and lake productivity. Phytoplankton has also been identified as sensitive to environmental change, with shifts in the seasonality of blooms, or phenology, resulting from changing temperature and nutrient conditions. A satellite remote sensing approach to r...

The 10-year archive of MEdium Resolution Imaging Spectrometer (MERIS) data is an invaluable resource for studies on lake system dynamics at regional and global scales. MERIS data are no longer actively acquired but their capacity for global scale monitoring of lakes from satellites will soon be re-established through the forthcoming Sentinel-3 Ocea...

Light within the littoral zone affects the productivity and interaction between periphyton and its macrophyte substrate. The effect of periphyton on macrophyte photosynthesis, seasonal variation and vertical distribution of periphyton on artificial substrates (plastic strips), and the effect of periphyton on the light environment was studied in Lak...

E-Mails: kovacs.attila@okologia.mta.hu (A.W.K.); zlinszky.andras@okologia.mta.hu (A.Z.); presing.matyas@okologia.mta.hu (M.P.); horvath.hajnalka@okologia.mta.hu (H.H.); toth.viktor@okologia.mta.hu (V.R.T.) 2 Centre for Landscape and Climate Research, University of Leicester, Bennett Building, University Road, Leicester LE1 7RH, UK; E-Mails: vnp2@le...

Despite longstanding contributions to oceanography, similar use of fluorescence light detection and ranging (LiDAR) in lake settings is not routine. The potential for ship-mounted, multispectral Ultraviolet Fluorescence LiDAR (UFL) to provide rapid, high-resolution data in variably turbid and productive lake conditions are investigated here through...

Plastic effect of environmental factors acting on an aquatic submerged plant, Potamogeton perfoliatus L. at the plant-level (nutrient availability) and the leaf-level (light intensity) at different sites in Lake Balaton was studied. Light-dependent morphological traits (foliar morphology and internode length) of P. perfoliatus were measured and ana...

Cyanobacteria are a worldwide group of photosynthetic prokaryotes that can cause nuisance blooms in eutrophic waters. It is generally accepted that their resting cells, akinetes, play an important role in the dispersal, recruitment, initiation of blooms and survival under unfavourable conditions, therefore information on the germination, distributi...

The effects of silicon on the growth and development of Phragmites australis (Cav.) Trin. Ex Steud. (common reed) stem nodal and root embryogenic calli were investigated. Silicon is considered to be a beneficial or quasi-essential nutrient for several Gramineaceous plants, including reed. Seven callus lines of four geographical locations (genotypes...

Phragmites australis is a stand forming emergent macrophyte that displays large phenotypic variation within the Lake Balaton. The present study assesses morphological variations of Phragmites australis within three transects of different reed stands of Lake Balaton which differ with respect to bathymetry, reed quality and geographic position in ord...

Comparative significance and synchronicity of morphological and photosynthetic adjustments of Potamogeton perfoliatus to shore-specific environments were examined on plants growing at the maximum depth of colonisation of the northern and southern shores of Lake Balaton. The shore-specific environments did not affect photophysiological parameters: t...

Wetlands are valuable habitats under considerable threat from human activity. Lake shore wetlands are especially suitable for aerial surveys, and aerial photogrammetry, hyperspectral imaging or airborne laser scanning are the usual methods applied. Lake Balaton is a large shallow lake with wetlands in decline since the 1970's. In August 2010, a ful...

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 photosynth...

Potamogeton perfoliatus readily adopts different morphological forms, and is therefore especially suitable for investigating variations of aquatic plants’ morphology according to different environmental conditions. This paper discusses the morphological diversity of P. perfoliatus at different sites in Lake Balaton, where it occurs as one of the d...

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...

The photosynthetic pigments and photochemical efficiency of photosystem 2 (PS2) were studied in four constitutive species (Achillea millefolium L., Festuca pseudovina Hack. ex Wiesb., Potentilla arenaria Borkh., and Thymus degenianus Lyka) of a semiarid grassland in South-eastem Hungary. Every species displayed typical sun-adapted traits and substa...

The influence of nitrogen deprivation on leaf development and the biomechanics of leaf growth were studied using maize (Zea mays L.) seedlings grown under low irradiance. Although the nitrogen deprivation had no significant effect on photosynthesis, the leaf length, the leaf area, and the total assimilation area of plants decreased. The mature size...

Investigations were performed on the interrelation between the photoprotective role of the xanthophyll cycle and levels of N-supply in maize plants (Zea mays L. cv. Maya). Plants were grown in non-fertilised and fertilised plots, while the latter were supplied with 30, 60, 90, 120 and 150 kg ha−1 NH4NO3 and grown under natural conditions in the fie...

The de-epoxidation process of violaxanthin to zeaxanthin induced by light was recognized a long time ago (Ref. 1), but it is only a recent achievement that the role of violaxanthin cycle components have been revealed as being decisive in heat dissipation of excess excitation energy in light harvesting complexes with respect to capacity for photoche...

In natural environment plants are continuosly subjected to the fluctuation in light conditions and their growth and survival basically depend on their capacity to acclimate their physiology, biochemistry and morphology (1). The function of photosynthetic apparatus in sun and shade adapted leaves and plants show considerable differences in terms of...