Csilla Stenger-Kovács

Epiphytic, littoral diatoms as bioindicators of shallow lake trophic status: Trophic Diatom Index for Lakes (TDIL) developed in Hungary

Littoral diatoms are important contributors of the primary production in shallow aquatic ecosystems and they can be used as indicators of the trophic status. The aim of the study was to develop an index to assess trophic status of Hungarian lakes as suggested by the Water Framework Directive. In spring of 2005 and 2006, epiphytic diatom samples were collected from 83 shallow lakes. Weighted average method was used to develop and test the TP model. In the developed TP model correlation between the observed and diatom inferred TP was high (r2 = 0.96, n = 67). The optimum and tolerance TP parametrics of 127 species were determined and trophic indicator and sensibility values were defined for the Trophic Diatom Index for Lakes (TDIL). The TDIL was applicable to assess the ecological status of Hungarian shallow lakes. According to the TDIL the ecological status of 4 lakes were in excellent, 25 in good, 21 in medium, 21 in tolerable and 12 in bad status.

Trait-based ecological classifications for benthic algae: review and perspectives

A high number of species often represents a relevant redundancy in terms of ecological adaptation strategies. Collecting species to groups based on their functional adaptations can handle this redundancy and obtain the “real” functional complexity of ecosystems. Functional traits are proxies of adaptation strategies under particular environmental conditions, and a set of functional traits are interpreted as life-strategies. Organisms with life-strategies occupying a similar niche can be collected in ecological groups (functional group/guild). In this study, we review the latest trait-based approaches and existing attempts at functional classifications in phytobenthos studies. Advantages and shortcomings of these classifications are discussed with perspectives of their utility in ecological status assessment.

Vanishing world: alkaline, saline lakes in Central Europe and their diatom assemblages

Abstract European shallow, alkaline, saline lakes are potential indicators of climate change. Diatoms have often been reported as valuable proxies for different kinds of anthropogenic activities. Diatom assemblages and 14 environmental variables from shallow, alkaline lakes from 2 different regions of the Carpathian basin (Europe) were investigated for 3 years to (1) elucidate the physical and chemical parameters and diatom assemblages of these lakes, (2) select the principle variables affecting the diatom communities, and (3) show the relevance of diatoms as ecological bioindicators. Water chemical characteristics of the lakes in the 2 regions differ significantly in anion concentrations (HCO3−, SO42−, and Cl−), platinum (Pt) units (colour), and oxygen saturation. Dominance by the stress-tolerant, motile diatom ecological guild, represented mainly by Nitzschia and Navicula species, was characteristic in these saline, turbid environments. Indicator species of the 2 regions were found to be different. Diatom assemblage composition was chiefly determined by conductivity and HCO3− and SO42−concentrations. Nutrient loads, extreme weather events, and consequences of habitat maintenance management were unequivocally identifiable by variations in the benthic diatom assemblage composition. Diatoms are valuable indicators for assessment of ecological status of these saline, alkaline lakes. Including these organisms in ecological status assessments of inland saline lakes may improve the effectiveness of directives for conservation management and might be useful in preserving these pristine habitats that depend on natural hydrological processes.

Application of water framework directive in Hungary: development of biological classification systems

The classification according to the Water Framework Directive (WFD) includes numerous challenges in contrast with the previously applied water qualification standards. The most important element of the ecological status, the biological one, is based on five groups of living organisms: phytoplankton, phytobenthon, macrophytes, macro-invertebrates and fish. The results of a three-year research project financed by the Ministry of Environment and Water (MoEW) and the Hungarian Academy of Sciences (HAS) are reported in this work. The objective of the project was the elaboration of a proposal for biological classification according to the WFD for the related groups of living organisms. In the course of the project the biological characteristics to be measured were selected for each of the above listed groups which served as the basic data for Biological Quality Elements (BQEs). In the BQEs we estimated the type-specific reference values for most of the Hungarian surface water types. Then we created the structure of the qualification system for these groups, including specification of class boundaries between the five classes for the Environmental Quality Ratio (EQR) values on the basis of expert estimation. A Non-Taxonomic Periphyton Index (NTPI, not included in the WFD) was also developed and tested for qualification. The elaborated classification systems were tested on the basis of existing scarce data for numerous Hungarian water types.

Coherence of phytoplankton and attached diatom-based ecological status assessment in Lake Balaton

Coherence between ecological status assessment by phytoplankton and attached diatoms was analyzed in the littoral zone of Lake Balaton. Sampling of periphytic diatoms, phytoplankton, and water were carried out at ten different littoral sites in the northern and southern shores of the lake for a year. Phytoplankton species were sorted into functional groups and ecological status was assessed by means of the phytoplankton assemblage Q index. The index TDIL was calculated using quantitative attached diatom data. Significant differences were found between the ecological assessments based on phytoplankton and phytobenthos metrics, both seasonally and spatially. The Q index indicated ecological states varying from bad to good, while the average of diatom indices varied from moderate to high conditions. The Q index provided more realistic ecological status of Lake Balaton, compared with trophic status based on TP values, especially in the summer period. Differences in the response-time indication of phytoplankton and attached diatoms suggest that lack of coherence should also be expected between the responses of other BQEs.

Establishment of equilibrium states and effect of disturbances on benthic diatom assemblages of the Torna-stream, Hungary

This paper analyses the establishment of equilibrium states in relation to natural disturbances in epilithic diatom assemblages. Sterilized limestone bricks were exposed between April 2008 and 2009 in the Torna-stream and were removed one by one on every third day in the first month and then weekly until May 2010. Physical and chemical parameters were measured on the field and in laboratory. Equilibrium states were restricted to three separate months: July 2008, May and January 2009 taking the consistence of biomass (chlorophyll-a) into consideration. Cocconeis placentula sensu lato, Fragilaria vaucheriae, Gomphonema parvulum, G. olivaceum, Naviculagregaria, N. lanceolata, Nitzschia linearis, and Surirella brebissonii took part in the equilibrium assemblages, two of which dominated by a single species. Analyses of environmental constancy during equilibrium phases allowed concluding that resilience of a developed equilibrium phase may ensure biotic constancy even though the underpinning environmental background fluctuates at higher amplitude. The conclusions of our study on attached stream diatom assemblages are similar to those found for temperate lakes: equilibrium states are rare, unpredictable, ephemeral, may occur both in relatively stable and strongly fluctuating environments, and are mostly characterized by monodominance, but contrary to phytoplankton, their establishment requires a longer time to develop corresponding to differences in generation times.

Environmental awareness of the permanent inhabitants of towns and villages on the shores of Lake Balaton with special reference to issues related to global climate change

Lake Balaton, one of the largest lakes in Europe, is an important centre for summer tourism in Hungary. The appearance of the water is, however, influenced by a number of physical and biological factors such as the frequency of storms, the hydrological balance, the water level and the growth of algae. Here we report the results of a survey designed to test the reaction of the local population to these seasonal and inter-annual variations. This survey was based on a questionnaire completed by 960 permanent inhabitants of the shoreline villages and was designed to explore their awareness of the local and regional factors responsible for the changes. About one-quarter of the respondents considered that the drying effects of global climate change had already had an effect on the Lake Balaton area. Although younger (16–26) and middle-aged (27–50) respondents benefit most from good water quality, those in the oldest age group (51–92) were more concerned about the quality of the water and broader issues such as biodiversity and the conservation of the landscape. Considering that the future of the lake depends on the youngest generation, this suggests that their environmental education could be improved to strengthen their understanding of environmental issues.

Application of benthic diatoms to assess efficiency of conservation management: a case study on the example of three reconstructed soda pans, Hungary

The number of shallow soda pans decreased drastically all over the world and their conservation needs to be urgently forced. Due to their unique physical and chemical features, the lack of appropriate management plans has been a worldwide issue. The aim of present paper was to study the efficiency of the applied water management in three Central European reconstructed soda pans based on their benthic diatom communities, physical and chemical parameters in the years 2012 and 2014. The diatom composition and the diversity metrics indicate unequivocally a worse ecological status of Borsodi-dűlő and Nyéki-szállás than it is characteristic for their natural conditions, which is attributable to their irregular water level modifications. The ecological status of the Legény-tó was far from the required because its conductivity was constantly low, diversity was high and the flora was dominated by mainly freshwater diatom species due to the lack of the natural hydrological cycle. However, these pans have significant conservation values; their good ecological status should be completely reached by restoring their natural hydrological and disturbance regimes.

Structuring forces and β-diversity of benthic diatom metacommunities in soda pans of the Carpathian Basin

ABSTRACT Small soda lakes represent one of the most vulnerable ecosystem types due to their high hydrological sensitivity to climate change and anthropogenic interventions. Since diatoms are excellent bioindicators, determining the β-diversity and the structuring dynamics of diatom metacommunities can provide valuable information for conservation planning for soda pans. In this study, two diatom metacommunities were surveyed monthly during a one-year period from distinct regions of the Carpathian basin: the Fertő-Hanság National Park (FH) between 2013 and 2014, and the Danube-Tisza Interfluve (DT) between 2014 and 2015. We explored whether β-diversity of diatom assemblages in the two regions is enhanced by species turnover or nestedness (related to richness differences) and investigated the role of deterministic and stochastic processes in shaping β-diversity patterns. Furthermore, we evaluated the contribution of environmental variables, geographic distance and temporal variation to community structure. High β-diversity (>90%) was revealed for both metacommunities, and was maintained primarily by species turnover. Within the metacommunity of the DT where the natural hydrological cycle of soda pans is not disturbed, diatom communities assembled mainly due to the selection force of environment at a spatiotemporal scale. In the soda pans located in the habitat reconstruction area of the FH, besides species-sorting, significant temporal variation in community structure appeared as a result of water management and periodic water supply. Our results point to the need for a conservation management strategy which maintains the natural hydrological regime of small saline lakes, and therefore their habitat heterogeneity which is of high conservation value.

Cymbella schmidtii Grunow transferred to Cymbopleura schmidtii (Grunow) Stenger-Kovács nov. comb. - A rare diatom species occurring in Lake Balaton (Hungary)

Taxonomic guides to a rare diatom species, Cymbella schmidtii Grunow, were reviewed because of a number of misunderstandings and insufficient documentation of this species. Accurate and detailed taxonomic features were described based on morphology (in light microscopy) and fine structure (in scanning electron microscopy), and the species was transferred to another genus, Cymbopleura (Krammer) Krammer. Not only were the morphological features clarified, but also the species distribution and occurrence as well. Cells of Cymbopleura schmidtii Stenger-Kovács nov. comb. occur as solitary individuals. The species was found in the littoral region of Lake Balaton (Hungary). It is not abundant, but is a characteristic diatom species of the lake, and is not restricted only to recent samples, but occurs also in fossil materials.