Publikációk

Carvalho et al., 2019 - Science of The Total Environment

Abstract

The Water Framework Directive (WFD) is a pioneering piece of legislation that aims to protect and enhance aquatic ecosystems and promote sustainable water use across Europe. There is growing concern that the objective of good status, or higher, in all EU waters by 2027 is a long way from being achieved in many countries. Through questionnaire analysis of almost 100 experts, we provide recommendations to enhance WFD monitoring and assessment systems, improve programmes of measures and further integrate with other sectoral policies. Our analysis highlights that there is great potential to enhance assessment schemes through strategic design of monitoring networks and innovation, such as earth observation. New diagnostic tools that use existing WFD monitoring data, but incorporate novel statistical and trait-based approaches could be used more widely to diagnose the cause of deterioration under conditions of multiple pressures and deliver a hierarchy of solutions for more evidence-driven decisions in river basin management. There is also a growing recognition that measures undertaken in river basin management should deliver multiple benefits across sectors, such as reduced flood risk, and there needs to be robust demonstration studies that evaluate these. Continued efforts in ‘mainstreaming’ water policy into other policy sectors is clearly needed to deliver wider success with WFD goals, particularly with agricultural policy. Other key policy areas where a need for stronger integration with water policy was recognised included urban planning (waste water treatment), flooding, climate and energy (hydropower). Having a deadline for attaining the policy objective of good status is important, but even more essential is to have a permanent framework for river basin management that addresses the delays in implementation of measures. This requires a long-term perspective, far beyond the current deadline of 2027.

Grigorszky et al., 2019 - Limnetica

ABSTRACT 

Drivers of the Ceratium hirundinella and Microcystis aeruginosa coexistence in a drinking water reservoir The spatial and temporal patterns of phytoplankton in relation to physical and chemical properties were studied in a drinking water reservoir - the Lázbérc Reservoir - located in north-east Hungary. The main objectives were to determine the role of the hydrologic regime in structuring algal growth and the effects of physical and chemical variables on the coexistence of a dominant species: cyanobacteria, Microcystis aeruginosa (Kützing) Kützing and an eukaryotic dinoflagellates, Ceratium hirundinella (O.F. Müller) Dujardin. The results suggest that nutrients (TP, NH4–N and NO3–N), turbidity, and the hydrologic regime play an important role in regulating the occurrence of investigated species. The rainy summer period resulting in a mixing of the water column, and the low level of nitrogen coupled with the internal release of phosphorus from the lake sediment under brief periods of anoxia promote cyanobacterial bloom. During this period, the water column was characterised by high turbidity, which created favourable conditions for developing a huge C. hirundinella biomass and the simultaneous occurrence of M. aeruginosa. This study also demonstrated - that contrary to what was previously known, deep standing waters in the temperate zone are not only dimictic (mixing twice a year during the spring and the fall), but they can also be mixed during the summer period due to continued rainfall, which equalizes the temperature in the whole water column. This can promote the occurrence of cyanobacterial and eukaryote planktonic organisms.

Selmeczy et al., 2019 - Hydrobiologia

Abstract

Analysis of a long-term (1994–2014) data set of phytoplankton and zooplankton in the deep, dimictic, oligo-mesotrophic Lake Stechlin (Germany) revealed trend-like changes: phytoplankton biomass and resource use efficiency increased with proliferation of heterocytic cyanobacteria (Dolichospermum spp. and Aphanizomenon flos-aquae), and those of especially large-sized zooplankton (Eudiaptomus, Eurytemora) decreased. These reverse trends are clear eutrophication symptoms and suggest a long-term trophic decoupling with potential decrease in energy transport towards higher tropic levels. Total phosphorus increased significantly over time; however, there is no known external P load for Lake Stechlin. Causality analysis enabled us to identify the primary reason of the observed changes. According to the results, stronger and longer-lasting stratification (measured as relative water column stability) drove the observed changes and the gradual regime shift was initiated by an extreme weather event—both indicating that climate change has been the crucial driver of the planktic community in this lake. Our study also documents that there might be decadal delays between cause and consequences in aquatic food webs, supporting the essential importance of long-term monitoring efforts.

Ujvárosi et al., 2019 - Science of The Total Environment

Abstract

Overproduction of toxic cyanobacteria is a type of harmful algal blooms (HABs). The heptapeptide microcystins (MCs) are one of the most common cyanotoxins. There is increasing research concerning the effects of MCs on growth and physiology of vascular plants, however there is a lack of studies on their direct effects on aquatic macrophytes in the real environment. Here we report the occurrence of a MC producing HAB in Lake Bárdos, Hungary in 2012 with harmful effects on cytological, histological and biochemical parameters of Ceratophyllum submersum (soft hornwort) plants naturally growing at the blooming site. Blue-Green Sinapis Test (BGST) showed high toxicity of HAB samples. Cell-free water samples contained a significant amount of MCs (7.31 ± 0.17 μg L−1) while C. submersum plants contained 1.01 ± 0.21 μg g DW−1 MCs. Plants showed significant increases of protein content and decreases of anthocyanin content and carotenoid/chlorophyll ratio, indicating physiological stress- as compared to plants from the control (MC free) sampling site of the same water body. Histological and cytological studies showed (i) radial swelling and the abnormal formation of lateral buds at the shoot tip leading to abnormal development; (ii) the fragmentation of nuclei as well as accumulation of phenolics in the nucleus indicating that the HAB induced cell death and stress reactions at the nuclear level. The most relevant effect was the increase of histone H3 phosphorylation in metaphase chromosomes: since MCs are strong inhibitors of protein phosphatases, this alteration is related to the biochemical targets of these toxins. The HAB decreased peroxidase activity, but increased nuclease and protease activities, showing the decreased capacity of plants to face biotic stress and as the cytological changes, the induction of cell death. This study is one of the first to show the complex harmful changes in aquatic plants that co-exist with HABs.

Hatvani et al., 2019 - Ecological Indicators

Abstract

Planktic algae have an essential role in the food web as primary producers; the determination of the ecological niche space occupied by them is thus essential in strategies aimed at sustaining the biodiversity of surface waters. In the present study, principal component analysis combined with the outlying mean index was applied to 14 water quality time series (1993–2005) derived from three previously determined homogeneous sections of the Hungarian part of the River Tisza. As a result, the seasonal distribution of the ecological n-dimensional hypervolumes was determined for the different river sections. In the first upper section, the seasonal niches overlay each other, and no clear separation could be detected. In the middle- and lower reaches, however, a clear separation between the seasons was observed. The identification of these separate niches of the various seasons as the main indicators/drivers of certain ecological communities (e.g. phytoplankton) proved possible.

Görgényi et al., 2019 - Hydrobiologia

Abstract

The functional group (FG) concept suggests that species having different phylogenetic origins but possessing similar functional characteristics can be considered as functional groups and these co-occur in the phytoplankton. Here, we study how functional redundancy of phytoplankton taxa (within group richness) contribute to the species diversity of assemblages in an oxbow lake in the Carpathian Basin. We found that although the observed functional redundancy was similar among several FGs, the shape of the species accumulation curves of these groups was considerably different, implying that the observed species numbers alone do not represent the real functional redundancy of the groups. We demonstrated that FGs that showed asymptotes in species richness estimates in small spatial scale, exhibited steady increase in large spatial, and temporal scales. The contribution of FGs to species richness depended strongly on the relative biomass of each FG. Species accumulation curves of those groups of which elements dominated in the phytoplankton, appeared to be approaching asymptotes. Since the shapes of species accumulation curves refer to the strengths of within-group competition among constituent species, our results imply that functional redundancy of phytoplankton is influenced by the role that the elements play within the assemblages.

Szabó et al., 2019 - Hydrobiologia

Abstract

In this study, driving forces and diversity patterns of a benthic diatom metacommunity across small freshwater lakes exhibiting environmental heterogeneity were investigated. Furthermore, local (LCBD) and species (SCBD) contributions to β-diversity and their driving parameters were assessed with abundance- and incidence-based analyses. Our results revealed that both spatial distance and environmental heterogeneity affected the community assembly, which corresponds most to the mass-effect (ME) concept. This theory was confirmed by high α-diversity of sampling sites; however, high overall β-diversity enhanced mainly by turnover contradicted the ME paradigm. LCBD indices were affected by environmental variables; furthermore, LCBD and LCBD in terms of species replacement showed a strong positive correlation. The ecologically most unique sites hosted relatively low species richness, and common species with intermediate-sized or broad niches contributed mostly to the regional β-diversity. However, abundance- and incidence-based calculations revealed different relationships of SCBD with the species’ total abundance and the number of occupied sites. Consequently, we favor the previous suggestions that comprehensive research focusing on conservation should incorporate the investigation of LCBD, SCBD, species-rich sites and also ecologically restricted species. Moreover, in assessing ecological uniqueness, both abundance and binary data sets should be considered since they might shed light on distinct patterns.

Muhl et al., 2018 - Ecology Letters

Abstract

 Allelopathic species can alter biodiversity. Using simulated assemblages that are characterised by neutrality, lumpy coexistence and intransitivity, we explore relationships between within‐assemblage competitive dissimilarities and resistance to allelopathic species. An emergent behaviour from our models is that assemblages are more resistant to allelopathy when members strongly compete exploitatively (high competitive power). We found that neutral assemblages were the most vulnerable to allelopathic species, followed by lumpy and then by intransitive assemblages. We find support for our modeling in real‐world time‐series data from eight lakes of varied morphometry and trophic state. Our analysis of this data shows that a lake's history of allelopathic phytoplankton species biovolume density and dominance is related to the number of species clusters occurring in the plankton assemblages of those lakes, an emergent trend similar to that of our modeling. We suggest that an assemblage's competitive power determines its allelopathy resistance.

Vasselon et al., 2018 - Methods in Ecology and Evolution

Abstract

1.         In recent years, remarkable progress has been made in developing environmental DNA metabarcoding. However, its ability to quantify species relative abundance remains uncertain, limiting its application for biomonitoring. In diatoms, although the rbcL gene appears to be a suitable barcode for diatoms, providing relevant qualitative data to describe taxonomic composition, improvement of species quantification is still required.

2.         Here, we hypothesized that rbcL copy number is correlated with diatom cell biovolume (as previously described for the 18S gene) and that a correction factor (CF) based on cell biovolume should be applied to improve taxa quantification. We carried out a laboratory experiment using pure cultures of eight diatom species with contrasted cell biovolumes in order to (1) verify the relationship between rbcL copy numbers (estimated by qPCR) and diatom cell biovolumes and (2) define a potential CF. In order to evaluate CF efficiency, five mock communities were created by mixing different amounts of DNA from the eight species, and were sequenced using HTS and targeting the same rbcL barcode.

3.         As expected, the correction of DNA reads proportions by the CF improved the congruence between morphological and molecular inventories. Final validation of the CF was obtained on environmental samples (metabarcoding data from 80 benthic biofilms) for which the application of CF allowed differences between molecular and morphological water quality indices to be reduced by 47%.

4.         Overall, our results highlight the usefulness of applying a CF factor, which is effective in reducing over‐estimation of high biovolume species, correcting quantitative biases in diatom metabarcoding studies and improving final water quality assessment.

Rimet et al., 2018 - Fottea

ABSTRACT

Diatoms are used routinely to assess pollution level in rivers and lakes. Current methods are based on identification by light microscopy, which is laborious. An alternative is to identify species based on short DNA fragments and High-Throughput Sequencing (HTS). However a potential limitation is the incomplete coverage of species in reference barcode libraries. Usually these libraries are compiled by isolating cells, before culturing and sequencing them, which is tedious and often unsuccessful. Here we propose the use of rbcL sequences from environmental samples analysed by HTS. We set several criteria to ensure good sequence quality and correspondence with the target species observed in microscopy: the sequence needed to be abundant in the sample, and with no insertions nor deletions or stop codon, phylogenetic neighbour taxa had to correspond to neighbour taxonomic taxa expected from morphological observations. Four species from tropical rivers are given as examples, including one that is new to science.

Schmera et al., 2018 - Freshwater Biology

Abstract

1.         Quantifying the relative importance of how local (environmental or niche‐based) and regional (dispersal‐related or spatial) processes regulate the assembly of communities has become one of the main research avenues of community ecology. It has been shown that the degree of isolation of local habitats in the landscape may substantially influence the relative role of environmental filtering and dispersal‐related processes in metacommunities.

2.         Dendritic stream networks are unique habitats in the landscape, where more isolated upstream sites have been predicted to be primarily structured by environmental variables, while more central mainstem rivers by both environmental and spatial variables (hereafter the network position hypothesis, NPH). However, the NPH has almost exclusively been tested for stream macroinvertebrates, and therefore its predictions warrant confirmation from multiple taxa.

3.         We examined the validity of the NPH for benthic diatoms, macrophytes, macroinvertebrates and fish in the Pannon Ecoregion, Hungary. Following the NPH we predicted a clear dominance of environmental over spatial variables in headwaters, and a larger effect of spatial variables in rivers compared to headwaters. We tested these predictions using variance partitioning analyses separately for the different taxa in headwater and in riverine habitats.

4.         We found large differences in the explained community variance when the impact of environmental (physical and chemical) and spatial (overland and watercourse distance) variables for various taxa was studied. In general, total explained variance was lower for the more passively dispersing plant taxa than for animal taxa with more active dispersal in both streams and rivers. However, similar to other studies, the total explained variance was low for both headwater streams and rivers.

5.         Community structure of diatoms could be best explained by both environmental and spatial variables in streams, whereas their community structure could not be explained by either variable group in rivers. The significance of environmental and spatial variables depended on the distance measure (overland versus watercourse) in the case of macrophytes. Community structure of macroinvertebrates could be explained by environmental variables in streams and by both environmental and spatial variables in rivers. Moreover, variation was explained by different predictors when macroinvertebrate taxa were divided into flying and non‐flying groups, suggesting the importance of dispersal mode in explaining community variation. Finally, community structure of fishes could be explained by both environmental and spatial variables in streams and only by environmental variables in rivers.

6.         In conclusion, we found no clear evidence of the NPH in our multi‐taxa comparison. For example, while patterns in macroinvertebrate communities seem to support the NPH, those in fish communities run counter with the predictions of the NPH. This study thus shows that different taxa may behave differently to isolation effects in stream networks. We discuss alternatives in the interpretation of dispersal (or spatial) effects which may partly explain differences in the observed patterns from the NPH, and emphasise the need for further studies in unravelling the importance of isolation in stream metacommunity structuring.

Buczkó et al., 2019 - Limnetica

ABSTRACT 

The first high resolution diatom record from Lake Balaton, Hungary in Central Europe A high-resolution diatom record of the last 7500 years of Lake Balaton, a large, shallow calcareous lake in Central Europe is presented here. Diatom analyses were carried out on a 112 cm long core obtained from the Siófok Basin (eastern part of the lake) combined with loss-on-ignition, geochemical measurements and grain-size analysis. Altogether 140 diatom taxa were distinguished in this study; Amphora pediculus, Cocconeis neothumensis, Fragilaria brevistriata and Karayevia clevei were frequent and ubiquitous members of diatom assemblages. Fragilaroid taxa were dominant through the core in the shallow Lake Balaton, but episodes of higher ratios of planktic forms (Lindavia balatonis, Aulacoseira granulata and Pantocsekiella ocellata) before ca. 2000 cal yr BP, indicated high water level in the lake, and stronger fluctuation than exists today. The diatom-based reconstruction of lake level was in accordance with the geochemical and zoological records, proving the usability of siliceous remains in paleolimnological reconstructions in Lake Balaton, in spite of the unfavourable preservation conditions.

Tóth et al., 2018 - Quaternary International

Abstract

Remains of aquatic biota preserved in mountain lake sediments provide an excellent tool to study lake ecosystem responses to past climate change. In the PROLONG project a multi-proxy study was performed on sediments of glacier-formed lakes from the Retezat Mountains, Southern Carpathians (Romania). The studied lakes (Lake Brazi and Gales) are situated on the northern slope of the mountain at different altitudes (1740 m and 1990 m a.s.l.). Our main objectives were 1) to describe the main limnological changes in these lakes during the last ca. 15,000 years and 2) to summarize the environmental history of the studied lakes based on taxonomical and functional patterns of the biological proxies. For this synthesis we used the results of diatom and chironomid analyses, and indirect biotic and abiotic parameters, including sediment organic matter (LOI) content, geochemical element concentrations (Al, Ca, S, Sr) and biogenic silica content. Using multivariate numerical approaches we analysed changes in the assemblage structure of siliceous algae and chironomids, compared temporal patterns among proxies, examined the relationship between potential driving factors, chironomid and diatom assemblage changes and identified paleolimnological phases of the lake successions. Changes in assemblage composition and aquatic ecosystem state apparently followed summer insolation, local climatic conditions and local productivity changes driven by these. Diatom and chironomid assemblages generally changed in a similar direction and at a similar time within a lake, but differed to some extent between Lake Brazi and Gales. At both lakes the strongest variations were observed in the Late Glacial and the first half of the Holocene. The strongest Holocene assemblage changes took place in the earliest Holocene in Lake Brazi, but extended into the mid-Holocene in Lake Gales, following long-term insolation changes and climatic changes. In addition, three common zone boundaries were identified: at ca. 14,200 and at ca. 6500 cal yr BP for every records and at ca. 3100 cal yr BP for diatom records in both of the lakes and for the chironomid record of Lake Brazi. This multi-proxy synthesis provides comprehensive data that increase our understanding of the past variability of lake ecosystem functioning and biodiversity in East-Central Europe.

Buczkó et al., 2018 - Quaternary International

Abstract

Climatic changes were studied using siliceous algae (diatoms and Chrysophytastomatocysts) analyses in four mountain lakes in the Retezat Mountains in the South-Carpathian Mountains with the aim to search for synchrony in aquatic ecosystem responses. According to the basal radiocarbon dating of the lake sediment cores, these lakes were formed around 17,000–15,000 cal yr BP. High resolution diatom analyses were carried out together with loss-on-ignition (LOI) and biogenic silica (BiSi) measurements on the lakes. Comparison of the proxy results suggests that despite the different slope aspect, water-depth and basin parameters, diatom assemblage changes show clear synchrony. The most remarkable changes in the aquatic ecosystems were observed around 6500 cal yr BP on the northern slope and around 6100 cal yr BP on the southern slope during the Holocene. Evidences for sharp concomitant shifts were found between 9200–9000 and 3200-3000 cal yr BP in the siliceous algal communities on both slopes. The Late Glacial/Holocene boundary was not pronounced in the shallow lakes, but was significant in a deep lake. The signs of a dry and bipartite Younger Dryas (GS-1) were evident, but floristic changes differed in the lakes. Principal component analyses explained very similar variances along the first and second axes for three lakes, while the fourth lake (Lake Bucura) proved less sensitive to climate change due to the dominance of moss-inhabiting diatom assemblages. Lake level changes have only been reconstructed on the basis of diatom life forms in one of the deep lakes (Lake Gales). High lake levels were inferred between 9300–9000 and 3000-1700 cal yr BP. In addition to LOI, biogenic silica content (BiSi) was measured on the sediments of the northern slope and pointed to different seasonal biological productivities; increasing LOI was often coupled with low BiSi values.

Pál et al., 2018 - Quaternary International

Abstract

As demonstrated by an increasing number of palaeoclimatic and palaeoecological studies, rapid climate change events (RCCs) occurred frequently in the Holocene and their timing correlates well in the European records. Changes in vegetation composition and environmental conditions were significant during these RCC events. In this study we use high resolution pollen, stomata, micro- and macrocharcoal, macrofossil, siliceous algae, biogenic silica and organic content analyses from two alpine lake sediments (Lake Brazi, 1740 m a.s.l.; Lake Gales, 1990 m a.s.l.) in the Retezat Mts, South Carpathian Mountains, Romania. Our aim is to study ecosystem responses to RCCs between 12,000 and 7000 cal yr BP using high-resolution proxy analyses of the relevant sediment sections. We detected several significant changes in the terrestrial vegetation composition and aquatic ecosystems in case of both lakes. Complex ecosystem responses were found in connection with the early Holocene RCC intervals. Most prominently, the 10.2 ka climatic change likely fostered the extinction of Larix decidua from the shore of Lake Brazi, while climatic change during the 8.2 ka event facilitated the establishment of Carpinus betulus in the lower deciduous mixed oak forests, due to decreasing growing season temperatures, frequent summer droughts and associated recurrent fire events. Taken together, most of the significant pollen compositional changes reflected the periodic spread of pioneer deciduous tree taxa (mainly Fraxinus excelsior and Corylus avellana) during the early Holocene RCCs. In all cases, this change was connectable to increased regional fire activity and the temporary increase of herbs. The most significant change in the lake-ecosystems was often the short-lived spread of various planktonic diatom species, mainly the members of genus Aulacoseira. Sudden appearance and large-scale percentage increase of these taxa suggested higher water-depth and/or intensified water turbulence.

Skibbe et al., 2018 - Diatom Research

Abstract

Colonies of a new, stalked diatom species Gomphoneis tegelensis sp. nov. were sampled in September 2017 from Lake Tegel (Berlin, Germany) where this large species was first observed in 2009. Cultivation was attempted several times without success. A single-cell DNA extraction method was therefore tried to yield molecular and morphological data from non-cultured specimens. Single cells were selectively picked off their stalks and their cell walls broken to release the DNA, as PCR and sequencing of intact cells provided no results. To improve yield, the DNA of several cells was pooled after PCR. The remaining intact cells were used for ultrastructural studies under SEM. The closely related species Gomphoneis transylvanica is typified as a basis for proper taxon identification and for comparison with the newly described species. Gomphoneis tegelensis differs from G. transylvanica and Gomphoneis ohridana mainly in its striation pattern and the number of rows of areolae in each stria. Molecular data confirm that G. tegelensis belongs to the Cymbellales, but it does not belong to the Gomphonemataceae.

Xiao et al., 2018 - Hydrobiologia

Abstract

Phytoplankton communities respond rapidly to environmental selection at a given locality, and they are also shaped by spatial processes at certain scales. The extracted effect of environmental selection and spatial processes may vary if different classification approaches are applied to phytoplankton and the spatial scales. In this study, summer phytoplankton of 43 lakes from three major lake regions in China were investigated and phytoplankton were classified with three approaches: taxonomy of species, habitat template-based functional groups, and morphology-based functional groups. Within a single lake region, the pattern of phytoplankton meta-community was significantly explained by environmental but not by spatial variables. In a larger scale covering all the three lake regions, both environmental and spatial variables explained the variance of the phytoplankton community, but the spatial variables were detected only by classification with species, and only the environmental variables were detected with phytoplankton functional groups. This study revealed that although vegetative populations of different species sorted into the same functional group have common response to environmental changes, their dispersal abilities, mechanisms, and strategies might differ markedly and therefore the species-specific approach cannot be disregarded when studying phytoplankton patterns at spatial scales.

Pálmai et al., 2018 - Acta Botanica Croatica

Abstract

Photosynthetic performances of two freshwater red algal populations from freshwaters of the Carpathian basin were measured in this study. Populations were collected from different habitats: Bangia atropurpurea from Lake Balaton and Batrachospermum gelatinosum from the Tapolca stream. Their photosynthesis was studied in a wide range of temperature (5–35 °C) and light intensity (0–1150 µmol m–2 s-1 ) in a photosynthetron. We found both species’ photosynthesis maxima at 25 °C but B. atropurpurea had significantly higher photosynthetic production. Low and medium values were calculated for the species’ photoadaptation parameters. Compensation light intensities determined in this study were similar to those obtained in previous studies. Both species utilized light efficiently; photoinhibition was detected only at two measuring temperatures for Bangia and at four measuring temperatures for Batrachospermum. P-T characteristics of the species revealed that both have temperature optima at 25 °C under high and medium light intensities but there are no such remarkable optima at low irradiance. The biomass specific respiration of both species increased with increasing temperature. We confirmed the good light utilization of these red algal species but found temperature optima higher than reported previously

Selmeczy et al., 2018 - Hydrobiologia

Abstract

A number of modelling results suggested thermocline shifts as a consequence of global climate change in stratifying lakes. Abundance and composition of the phytoplankton assemblage is strongly affected by the stratification patterns, and therefore, change in the thermocline position might have a substantial effect on this community or even on the whole lake ecosystem. In this study, thermocline depths in large mesocosms installed in Lake Stechlin (Germany) were deepened by 2 meters and phytoplankton changes were analysed by comparing changes to untreated mesocosms. Higher amounts of SRP were registered in the hypolimnion of treatment mesocosms than in the controls, and there were no differences in the epilimnion. Small but significant changes were observed on the phytoplankton community composition related to the effect of deepening the thermocline; however, it was weaker than the yearly successional changes. The most remarkable differences were caused by Planktothrix rubescens and by chlorophytes. P. rubescens became strongly dominant at the end of the experiment in the mesocosms, and in the open lake as well. The results of the experiment cannot clearly support the proliferation of cyanobacteria in general; however, the deepened thermocline can modify the behaviour of some species, as was observed in case of P. rubescens.

Bácsi et al., 2018 - Algal Research

Abstract

The economic role of certain types of cysts is unquestionable, since the production of several valuable biomolecules is connected to the resting stages of algae, including the red ketocarotenoid astaxanthin. It is relatively well known, how adverse environmental conditions induce cyst formation and astaxanthin accumulation. In the contrary, there is very limited information about stressors inhibiting these processes. An undesirable consequence of increasing drug use of the human and veterinary medicine is the appearance of the drugs both in natural and in mains water. Therefore, to study the effects of micro-contaminants, e.g. pharmaceuticals to non-target aquatic organisms is a recent issue both from ecological and economical point of view. In this study, the effects of three non-steroidal anti-inflammatory drugs (NSAIDs: diclofenac, diflunisal and mefenamic acid) on growth, cyst formation and astaxanthin accumulation of the flagellated green alga Haematococcus pluvialis were investigated. All three drugs inhibited growth, inhibition ranged from 29 to 81% on the basis of vegetative cell numbers on the 14th day of the experiments. Higher concentrations of the drugs led to higher proportion of cysts, which exceeded 60% of total cell number to the 14th day in diclofenac and diflunisal treatments. On the contrary, astaxanthin contents of treated cultures were lower with the increasing drug concentration, the pigment was undetectable in the presence of 0.075 and 0.05 mg ml−1 diclofenac. Results of carotenoid and chlorophyll content analysis suggest more specific processes behind the observed phenomena than membrane damage. Furthermore, the different phenomena or different extents of the same phenomena suggest that NSAIDs with diverse chemical structures may have different target points in physiological processes. Our results clearly show that NSAIDs could have much wider effective spectra than expected, long-term effectson microalgae might have unexpected ecological or economical consequences due to continuous exposure to these chemicals.

Dobronoki et al., 2018 - Journal of Applied Phycology

Abstract

Some literature data suggest that one of the possible roles of the cyanotoxin cylindrospermopsin (CYN) is forcing other phytoplankton species in the environment to produce alkaline phosphatase, which enables the cyanobacterium to take up the enzymatically liberated phosphate. In this study, cultures of a planktonic green alga, Scenedesmus obtusus (Chlorophyta, Sphaeropleales), were treated with CYN producer Aphanizomenon (Cyanobacteria, Nostocales) crude extract (C+), with non-CYN producer Aphanizomenon crude extract (C−), and with non-CYN producer Aphanizomenon crude extract supplemented with CYN (C−+C). The results showed that C+ treatment induced both acidic and alkaline phosphatases of the studied cosmopolitan green alga, which otherwise was neither sensitive to the relatively high CYN concentration, nor to phosphate limitation. In cases of C− and C−+C treatments, these phenomena were not observed. Several studies suggest that additional compounds may support CYN action. The results presented here suggest in a more direct way that other components present in the cellular matrix of the producer organism itself are involved in the effects of CYN, activation of phosphatases (not only alkaline ones) among them. These other components are absent in C− crude extract or cannot actively contribute to the effects of exogenously added CYN.

Garda et al., 2018 - Frontiers in Plant Science

Abstract

Horseradish allyl isothiocyanate (AITC, a volatile oil) and cyanobacterial microcystin-LR (MCY-LR, a cyclic heptapeptide) affect eukaryotic cell cycle. MCY-LR inhibits protein phosphatases PP1 and PP2A. We aimed to reveal the mechanisms of their cellular effects in a model eukaryote, Vicia faba. We have shown for the first time that AITC had minor effects on PP1 and PP2A activities in vitro, but it inhibited significantly PP1 in vivo. The combination of 10 μM AITC with 10 μM MCY-LR induced metaphase arrest after short-term (12 h) treatments. 10 μM AITC, 0.2–10 μM MCY-LR and their combinations induced histone H3 hyperphosphorylation, associated with the regulation of metaphase-anaphase transition. This hyperphosphorylation event occurred at any treatment which led to the inhibition of PP1 activity. 10 μM AITC + 10 μM MCY-LR increased the frequency of metaphase spindle anomalies, associated with metaphase arrest. We provide new insights into the mechanisms of metaphase-anaphase transition. Metaphase arrest is induced at the concomitant hyperphosphorylation of histone H3, alteration of metaphase spindle assembly and strong inhibition of PP1 + PP2A activity. Near-complete blocking of metaphase-anaphase transition by rapid protein phosphatase inhibition is shown here for the first time in plants, confirming a crucial role of serine-threonine phosphatases in this checkpoint of cell cycle regulation. Tissue-dependent differences in PP1 and PP2A activities induced by AITC and MCY-LR suggest that mainly regulatory subunits are affected. AITC is a potential tool for the study of protein phosphatase function and regulation. We raise the possibility that one of the biochemical events occurring during AITC release upon wounding is the modulation of protein phosphatase dependent signal transduction pathways during the plant defense response.

Nagy et al., 2018 - Journal of Food Composition and Analysis

Abstract

The freshwater cyanobacterium Cylindrospermopsis raciborskii was investigated for carotenoid composition. Besides β-carotene, echinenone and (9/9′Z)-echinenone a carotenoid glycoside was found to be the main component. This compound was isolated and subsequently acetylated for structural elucidation. The acetyl derivative was fully characterized by UV–vis, ECD, NMR and HRMS techniques. The detailed 1H and 13C NMR chemical shift assignment of the major carotenoid supported the unequivocal identification of (2′S)-2-hydroxymyxol 2′-α-l-fucoside.

Bell et al., 2018 - Antonie van Leeuwenhoek

Abstract

The Carpathian Basin is a lowland plain located mainly in Hungary. Due to the nature of the bedrock, alluvial deposits, and a bowl shape, many lakes and ponds of the area are characterized by high alkalinity. In this study, we characterized temporal changes in eukaryal and bacterial community dynamics with high throughput sequencing and relate the changes to environmental conditions in Lake Velence located in Fejér county, Hungary. The sampled Lake Velence microbial populations (algal and bacterial) were analyzed to identify potential correlations with other community members and environmental parameters at six timepoints over 6 weeks in the Spring of 2012. Correlations between community members suggest a positive relationship between certain algal and bacterial populations (e.g. Chlamydomondaceae with Actinobacteria and Acidobacteria), while other correlations allude to changes in these relationships over time. During the study, high nitrogen availability may have favored non-nitrogen fixing cyanobacteria, such as the toxin-producing Microcystis aeruginosa, and the eutrophic effect may have been exacerbated by high phosphorus availability as well as the high calcium and magnesium content of the Carpathian Basin bedrock, potentially fostering exopolymer production and cell aggregation. Cyanobacterial bloom formation could have a negative environmental impact on other community members and potentially affect overall water quality as well as recreational activities. To our knowledge, this is the first prediction for relationships between photoautotrophic eukaryotes and bacteria from an alkaline, Hungarian lake.

Lukács et al., 2018 - Hydrobiologia

Abstract

Single-trait analyses are used to select the most appropriate species characteristics for an effective indication of changes in multiple stressors, but they are robust to detect fine-scale functional changes in biofilms. The combination of single traits may appropriately reflect ecological properties of changing benthic assemblages. We studied colonisation processes of benthic algal assemblages focusing on the changes in trait composition using life forms, type of attachments, cell size and mobility as single traits in a small lowland stream. We tested the descriptive power of single-trait groups (STGs) and also combined trait groups (CTGs). We assumed that STGs would be significantly affected by environmental factors, but compositional changes in biofilms would be described more easily by using CTGs rather than STGs. Our hypotheses were confirmed by the results. While some STGs correlated positively to environmental factors indicating disturbances, others correlated to environmental factors indicating the stable conditions. The fast settlement of large-sized groups was also relevant determining the compositional changes in the studied benthic community. Despite the strong correlation between STGs and environmental variables, CTGs analyses revealed important functional relations in the ecosystem, since CTGs display more sophisticated functional features of the organisms, which may provide more realistic responses.

Földi et al., 2018 - PlosOne

Abstract

The spatial response of epiphytic diatom communities to environmental stress was studied in a moderately saline wetland area located in the plain of Danube-Tisza Interfluve, Hungary. The area is characterised by World War II bomb crater ponds and can be regarded as an excellent ecological model system where the dispersion of species is slightly limited by distance. To study the effect of environmental variables on the communities, canonical correspondence analysis was applied. Salinity, pH, total suspended solids, total phosphorous and depth proved to be significant environmental drivers in this analysis. The ecological status of the ponds was assessed with Ziemann’s halobity index, as the trophity-depending metric cannot be applied to these habitats (due to the naturally high phosphorus content). Ponds in “good” ecological status significantly differed from those appertaining to water quality category of “not-good” ecological status considering characteristic of natural astatic soda pans (e.g. salinity, pH, ammonium, total phosphorous concentration, nitrogen:phosphorous ratio and turbidity). The differences between epiphytic diatom communities inhabiting the ponds were detected using non-parametric multidimensional scaling. The samples formed three groups according to the types of ponds (“transparent”, “transitional” and “turbid”) based on the width of the macrophyte belt around them. Indicator species related to the ecological status of the ponds and diatom communities contributing to the separation of groups of ponds were identified. One of the indicator species differed from species already described. Light and scanning electron microscopy features and phylogenetic analyses based on three genes (18S and 28S rRNA genes, rbcL) proved that it was a new species of Nitzschia genus, closely related to Nitzschia frustulum and Nitzschia inconspicua. Therefore, description of a new species, Nitzschia reskoi Ács, Duleba, C.E.Wetzel & Ector is proposed. We concluded that the increasing abundance of Nitzschia reskoi was a signal of the degradation of the intermittent saline wetlands.

Endrédi et al., 2018 - Community Ecology

Abstract

We briefly discuss the relationship between the biological knowledge and the methodological issues related to traitbased ecological analyses. We provide illustrative examples and argue that the biological novelty of trait-based research is generally less than expected - while new information is mostly coming from data management and methodology.

Selmeczy et al., 2018 - Hydrobiologia

Abstract

Analysis of a long-term (1994–2014) data set of phytoplankton and zooplankton in the deep, dimictic, oligo-mesotrophic Lake Stechlin (Germany) revealed trend-like changes: phytoplankton biomass and resource use efficiency increased with proliferation of heterocytic cyanobacteria (Dolichospermum spp. and Aphanizomenon flos-aquae), and those of especially large-sized zooplankton (Eudiaptomus, Eurytemora) decreased. These reverse trends are clear eutrophication symptoms and suggest a long-term trophic decoupling with potential decrease in energy transport towards higher tropic levels. Total phosphorus increased significantly over time; however, there is no known external P load for Lake Stechlin. Causality analysis enabled us to identify the primary reason of the observed changes. According to the results, stronger and longer-lasting stratification (measured as relative water column stability) drove the observed changes and the gradual regime shift was initiated by an extreme weather event—both indicating that climate change has been the crucial driver of the planktic community in this lake. Our study also documents that there might be decadal delays between cause and consequences in aquatic food webs, supporting the essential importance of long-term monitoring efforts.

Várbíró et al., 2018 - Hydrobiologia

Abstract

The impact of cumulative daily solar radiation (CDSR) on the biomass of river phytoplankton (Chl-a) in the growing season was studied using a large dataset of rivers in the Carpathian Basin. The amount of solar radiation was cumulated over the range of 1–60 days. The CDSR–Chl-arelationship could be described by linear regression and appeared to be significant for almost all watercourses with the exception of rivers with short water residence time. To determine the most relevant time period of CDSR impacting phytoplankton biomass, the slopes of regressions were plotted against the accumulating number of days of light exposure (1–60). Two characteristic shapes were obtained: unimodal for rhithral rivers with hard substrate and steady increase for lowland potamal rivers with fine substrate. In both cases, there is an increasing tendency in the slope values with water residence time (WRT). It was demonstrated that CDSR has a pronounced impact on river phytoplankton biomass even in cases when WRT was shorter than the cumulated solar radiation period. These results indicate that development of phytoplankton within the river channel is a complex process in which meroplankton dynamics may have significant impacts. Our results have two implications: First, CDSR cannot be neglected in predictive modelling of riverine phytoplankton biomass. Second, climate models forecast increased drought with subsequently increased CDSR in several regions globally, which may trigger a rise in phytoplankton biomass in light-limited rivers with high nutrient concentrations.

Abonyi et al., 2018 - Freshwater Biology

Abstract

1.         Long‐term dynamics of phytoplankton have been addressed in marine and lake systems, but rarely in rivers. Large rivers, however, are highly human‐impacted, whereas global warming may further affect the functioning of phytoplankton at long‐term scale.

2.         In the middle section of the large European Danube River, long‐term decrease in phytoplankton biomass (Chl‐a) and increase in species diversity have formerly been revealed. The functional community composition that relates to ecosystem functioning directly has not been addressed previously. We analyse a 34‐year‐long phytoplankton data set from the middle river section at Göd (N‐Budapest), Hungary. We focus on gradual changes in the functional composition and functional diversity components based on the functional trait and functional group approaches.

3.         We hypothesised that long‐term gradual changes in major environmental constraints should be followed by gradual shifts in dominance relationships among functional traits and functional groups of phytoplankton. We further hypothesised that functional shifts were highlighted by gradual changes in functional diversity components: evenness, divergence and dispersion.

4.         Water discharge of the middle Danube shifted towards the more frequent occurrence of lower values. On the other hand, high floods (>3,000 m3/s) increased significantly with shortening tendency in duration and altered seasonality. The concentration of N and P forms, as well as total suspended solids decreased significantly. Water temperature increased significantly, especially in summer. In the phytoplankton, single‐celled eutrophic centric diatoms decreased in relative abundance, but flagellated, elongated and filamentous forms increased. A clear functional shift was the dominance decrease in planktonic taxa and the relative abundance increase in benthic diatoms.

5.         All functional diversity components increased significantly in the entire data set, except functional evenness (FEVE) based on the functional group approach. At seasonal scale, all significant trends showed increases, except the FEVE components of the functional group approach, which decreased in winter and spring significantly.

6.         Long‐term increase in functional diversity components alone could indicate enhanced ecosystem functioning of phytoplankton in the middle section of the Danube. However, we argue that the observed increase in functional diversity may be related to a gradual shift from high‐biomass communities with the dominance of eutrophic centric diatoms towards the relative increase in several, but low‐biomass elements. These include a few planktonic algae well adapted to the altered conditions, diatoms with benthic origin and dispersed limnophilic taxa.

7.         Our results provide the first evidence for a long‐term phytoplankton functional regime shift in a European large river. Global warming, human impacts and oligotrophication might potentially increase the functional diversity of large river phytoplankton, but the origin and functional role of taxa should carefully be considered. The observed functional shift in phytoplankton might also be indicative for alterations in the food‐web structure of the middle section of the Danube River at long‐term scale.

Abonyi et al., 2018 - Freshwater Biology

Abstract

1.         Recent studies clearly support a positive biodiversity–ecosystem functioning (BEF) relationship in phytoplankton. As taxon richness does not quantify functional diversity, functional approaches have been developed to link community functioning to diversity. Compared to terrestrial plant communities, only a few studies have validated phytoplankton functional approaches in BEF relationships. Furthermore, the ability of functional and taxonomic richness measures in predicting ecosystem functioning of natural phytoplankton communities has not been compared yet.

2.         Here, we analysed the BEF relationship using taxonomic and functional (trait categories and response groups sensu Reynolds) approaches in a broad‐scale phytoplankton dataset from Fennoscandia. First, we analysed how taxonomic and functional compositions were related to local environmental predictors. We then compared how taxonomic and functional richness performed in predicting resource‐use efficiency (the yield in phytoplankton biomass standardised by total phosphorus) as an ecosystem functioning measure. Finally, we tested whether the relationship between ecosystem functioning and taxonomic richness is further enhanced once each of the functional richness measure is also considered.

3.         Among the approaches, phytoplankton functional trait categories as community matrix showed the best correspondence with the local environment. The richness of phytoplankton response groups predicted ecosystem functioning significantly better than the taxonomic and the functional trait category richness—both in the full dataset and in almost all Fennoscandian countries. On top of taxonomic richness, only the residual variation in response group richness predicted ecosystem functioning positively in the entire dataset and in all individual countries.

4.         Applying functional approaches, reduced complexity of data should come along with reduced ecological information. We showed, however, that both functional approaches represented some functional redundancy among taxa in a meaningful way, and enhanced our ability in predicting community composition from environmental predictors. Moreover, phytoplankton response group richness sensu Reynolds summarises information on ecosystem functioning contained in the taxonomic data in a way that represents functional diversity better than the richness of functional trait categories.

5.         Interestingly, the response group approach, which is exclusively derived from field observations rather than from quantified phytoplankton traits, outperforms taxonomic richness and trait category richness in predicting ecosystem functioning in our dataset. This may highlight that our ability to quantify phytoplankton traits is still limited. Existing phytoplankton functional approaches, however, can translate the taxonomic information into a reduced but reliable functional matrix already and predict ecosystem functioning better than taxonomic data.

Stenger-Kovács et al., 2018 - Ecological Indicators

Abstract

Shallow, saline inland lakes occur over large areas in Central-Europe and they bear exceptionally high biological conservation values. Climate change and anthropogenic activities threaten their natural conditions, or even their existence. These aquatic ecosystems are exposed to multiple stress like naturally high conductivity, pH and nutrient load with very low transparency for light. As they are subjects of criteria set by the EC Water Framework Directive and biological conservation managment, there is an urgent need for developing a suitable quality index for their ecological status assessment. As one major Biological Quality Element, benthic diatoms may provide a reliable basis for their ecological status indication. Here, in a large data set covering the soda lakes of the Carpathian basin, we developed a species- and a trait-based diatom ecological status index. First, based on the weighted average method, we developed a type specific, species-based diatom index (DISP = Diatom Index for Soda Pans) using conductivity as master variable of environmental constrains; and therefore the ecological status in soda lakes. Furthermore, by adapting and improving further the widely-used diatom ecological guild concept, we also developed an alternative trait-based index, which helps avoiding some limitations arising from the obvious complexity of the taxonomy-based approach. Our DISP index covered a significantly larger species pool for index calculation, and responded to conductivity in a more reliable way compared to other available indices. In the trait-based index (TBI) motility, small cell size, and less roundish, more elongated shape as functional and morphological traits indicated pristine ecological conditions (i.e high conductivity) of the soda pans. Planktic life form, high and low ecological guild profiles, as well as the large cell size indicated worse ecological conditions (e.g. lower conductivity). Our study highlights that benthic diatoms provide a reliable basis for ecological status assessment in soda lakes. While both the taxonomic and the functional trait approaches performed well in our analysis, the success of the trait-based approach may enable the use of our TBI index in biomonitoring and conservation management of soda lakes outside of the Carpathian basin, independently of the geographic location.

Wang et al., 2018 - Hydrobiologia

Abstract

The occurrence of benthic diatoms in large river plankton is considered to be highly stochastic. Accordingly, the widely applied phytoplankton functional group concept sensu Reynolds (FG) classifies all benthic diatom taxa together. Based on data of a high-frequency 1-year long phytoplankton survey of the Pearl River (China), we tested whether the combination of the FG system with various trait-based classifications of benthic diatoms enhances our ability in predicting the community composition from the local environment. Using the Self-Organizing Map approach, we identified characteristic community compositions based on (i) taxonomic data, (ii) the FG approach, and (iii) the FG system combined with trait-based functional approaches of benthic diatoms: size structure, ecological guilds, and eco-morphological groups. All combined functional approaches enabled better predictions for the community composition than the taxonomic data or the FG system alone. The most reliable approach was the combination of the FG system with ecological guilds of benthic diatoms. Therefore, the occurrence of benthic diatoms in large river phytoplankton can be assessed ecologically in a meaningful way based on combined planktic and benthic functional classifications. The application of this approach seems to be highly relevant in large river phytoplankton ecology, ecological modelling, or in ecological status indication.

Szabó et al., 2018 - European Journal of Phycology

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.

Tapolczai et al., 2018 - Ecology and Evolution

Abstract

Extensive studies on the taxonomic resolution required for bioassessment purposes have determined that resolution above species level (genus, family) is sufficient for their use as indicators of relevant environmental pressures. The high‐throughput sequencing (HTS) and meta‐barcoding methods now used for bioassessment traditionally employ an arbitrary sequence similarity threshold (SST) around 95% or 97% to cluster sequences into operational taxonomic units, which is considered descriptive of species‐level resolution. In this study, we analyzed the effect of the SST on the resulting diatom‐based ecological quality index, which is based on OTU abundance distribution along a defined environmental gradient, ideally avoiding taxonomic assignments that could result in high rates of unclassified OTUs and biased final values. A total of 90 biofilm samples were collected in 2014 and 2015 from 51 stream sites on Mayotte Island in parallel with measures of relevant physical and chemical parameters. HTS sequencing was performed on the biofilms using the rbcL region as the genetic marker and diatom‐specific primers. Hierarchical clustering was used to group sequences into OTUs using 20 experimental SST levels (80%–99%). An OTU‐based quality index (IdxOTU) was developed based on a weighted average equation using the abundance profiles of the OTUs. The developed IdxOTU revealed significant correlations between the IdxOTU values and the reference pressure gradient, which reached maximal performance using an SST of 90% (well above species level delimitation). We observed an interesting and important trade‐off with the power to discriminate between sampling sites and index stability that will greatly inform future applications of the index. Taken together, the results from this study detail a thoroughly optimized and validated approach to generating robust, reproducible, and complete indexes that will greatly facilitate effective and efficient environmental monitoring.

Bolgovics et al. (2017): Fundamental and Applied Limnology

Bolgovics Ágnes, Ács Éva, Várbáró Gábor, Görgényi Judit, Kiss Keve Tihamér, Földi Angéla, Nagy-László Zsolt, Trábert Zsuzsa, Borics Gábor: Benthic diatom-based lake types in Hungary

Abstract

Hydromorphological and chemical properties of water bodies have pronounced influence on the occurrence and distribution of biological elements in the aquatic ecosystems. Based on a series of abiotic characteristics, seventeen lake types were established in Hungary for management purposes. Benthic diatom assemblages were studied in shallow standing water bodies in Hungary in order to provide a biological validation of these types. Species composition and abundance of the occurring taxa were analysed. By their diatom taxonomic composition five basic lake types could be distinguished; two calcareous lake types, which differ in size and in their trophic characteristics and three types within the group of high salinity lakes. In this latter group the astatic and perennial lakes showed considerable differences. These results have great practical importance, because biological validation of the hydromorphological lake typology is the first step for reliable assessment of the ecological status of water bodies.

Kralj Borojević et al. (2017): Acta Botanica Croatica

Kralj Borojević K, Gligora Udovič M, Žutinić P, Várbíró G, Plenković-Moraj A: Do benthic diatom assemblages reflect abiotic typology: a case study of Croatian streams and rivers

Abstract

Benthic diatoms are widely used in Europe and worldwide to access ecological status of running waters. One of key goals of Water Framework Directive is to classify rivers and streams using biological quality elements and type specific reference conditions. According to system B which incorporates additional abiotic descriptors, there are 24 water types in Croatia. For biological analyses 92 rivers and streams with 140 sampling points were chosen and sampled for benthic diatoms and water chemistry simultaneously. Self organizing map (SOM) analysis was used to define biotypes from species composition and abundance of benthic diatoms. Grouping of samples in SOM resulted in 10 distinctive groups. Based on their geographical position and site characteristics, groups represent sites with similar properties (as waterbed, catchment size, altitude, size of stream) belonging to different ecoregions in Croatia. Analysis of variance revealed statistically significant differences (p < 0.05) among SOM groups concerning ammonia, nitrates and total phosphorus. Indicator species analysis (IndVal) singled out species that were significantly characteristic (p < 0.05) for SOM and abiotic types. Compared to abiotic groups, in which 7 out of 24 have no indicator species, all SOM groups have one or several characteristic diatom species, thus indicating diatom assemblages as valuable site descriptors. Canonical analysis of principal coordinates analysis also indicated that SOM grouping of samples is statistically reliable. Grouping of similar sites, although placed into different abiotic types, makes SOM groups with its corresponding representative species an easy tool for water quality assessment and description of reference assemblage.

Abd-Ellatif et al. (2016): International Journal of Applied Environmental Sciences Research

Abd-Ellatif M. Hussian, Abd El-Hady Howayda H. , Toufeek MEF, Várbiro G: Phytoplankton Structure biochemical Stoichiometry and elemantal comnosition in Lake Nasser Egypt

Abstract

The relationship between environmental variables and elemental, biochemical composition of phytoplankton species in Lake Nasser were studied. In the lake 130 phytoplankton species were recorded, the lake is dominated mainly by Cyclotella glomerata (Bacillariophyceae), Planktolyngbya limnetica, Eucapsis minuta (Cyanophyceae). Phytoplankton organic carbon content at the lake was 32%. The elevation of NO₃^- (365 µg/l) and CO₃^- (21 mg/l) at the east of the lake was concurrently with the highest proportion of inorganic C, N and algal protein content. C/N ratio decreased thus Redfield ratio indicating a high growth rate of phytoplankton with increasing protein content. C/H and O/C ratio for natural phytoplankton samples were less than one, which means unsaturated aliphatic compounds at metabolites categories of phytoplankton. RDA analysis cleared that, Cyclotella glomerata (dominant at the north area) was sensitive to flushing, tolerant to nutrient deficiency and had higher protein content. Planktolyngbya limnetica (dominant at the middle) was more sensitive to pH, phosphorus is non-limiting factor and characterized by elevation in lipid content. Eucapsis minuta (dominant at the south) was tolerant to mild light deficiency and contains a maximum value of carbohydrates and Chlorophyll a.

Bácsi et al. (2016): Environmental Pollution

Bácsi I, B-Béres V, Kókai Z, Gonda S, Novák Z, Nagy SA, Vasas G: Effects of non-steroidal anti-inflammatory drugs on cyanobacteria and algae in laboratory strains and in natural algal assemblages

Abstract

In recent years measurable concentrations of non-steroidal anti-inflammatory drugs (NSAIDs) have been shown in the aquatic environment as a result of increasing human consumption. Effects of five frequently used non-steroidal anti-inflammatory drugs (diclofenac, diflunisal, ibuprofen, mefenamic acid and piroxicam in 0.1 mg ml⁻¹concentration) in batch cultures of cyanobacteria (Synechococcus elongatus, Microcystis aeruginosa, Cylindrospermopsis raciborskii), and eukaryotic algae (Desmodesmus communis, Haematococcus pluvialis, Cryptomonas ovata) were studied. Furthermore, the effects of the same concentrations of NSAIDs were investigated in natural algal assemblages in microcosms. According to the changes of chlorophyll-a content, unicellular cyanobacteria seemed to be more tolerant to NSAIDs than eukaryotic algae in laboratory experiments. Growth of eukaryotic algae was reduced by all drugs, the cryptomonad C. ovata was the most sensitive to NSAIDs, while the flagellated green alga H. pluvialis was more sensitive than the non-motile green alga D. communis. NSAID treatments had weaker impact in the natural assemblages dominated by cyanobacteria than in the ones dominated by eukaryotic algae, confirming the results of laboratory experiments. Diversity and number of functional groups did not change notably in cyanobacteria dominated assemblages, while they decreased significantly in eukaryotic algae dominated ones compared to controls. The results highlight that cyanobacteria (especially unicellular ones) are less sensitive to the studied, mostly hardly degradable NSAIDs, which suggest that their accumulation in water bodies may contribute to the expansion of cyanobacterial mass productions in appropriate environmental circumstances by pushing back eukaryotic algae. Thus, these contaminants require special attention during wastewater treatment and monitoring of surface waters.

B-Béres V et al. (2016): Ecological Indicators

B-Béres V, Lukács Á, Török P, Kókai Zs, Novák Z, T-Krasznai E, Tóthmérész B, Bácsi I: Combined eco-morphological functional groups are reliable indicators of colonisation processes of benthic diatom assemblages in a lowland stream

Abstract

Classifying benthic diatom taxa based on ecological and morphological features became increasingly important in recent years due to the demand of understanding the dynamics and functioning of diatom assemblages. The great potential in using these functional classifications in diatom ecology involves further refinement of current classification. In our experimental study, colonisation processes of diatom assemblages were studied in a typical small lowland stream, using both diatom guilds and cell size categories. We also tested newly proposed combined eco-morphological functional groups (ecological guilds combined with cell size categories) in the study of the colonisation process in benthic diatom assemblages. We hypothesised that (i) there is a decrease in the proportion of low profile guild, while an increase in that of high profile and motile guilds in time with the decreasing rate of physical disturbance; (ii) the presence of small size categories will be pronounced at the beginning of the colonisation processes, while proportion of larger size categories will be higher in the latter phases of colonisation; and (iii) the relationship between taxa and environmental factors are better reflected by the use of combined eco-morphological functional groups than by the sole analyses of rough guilds or cell size categories. The first hypothesis was not confirmed, and our second hypothesis was only partially confirmed by the results. We found that the relationship between environmental factors and guilds, as well as cell size categories was not appropriate to reveal the relationship between abiotic factors and taxa composition. In contrast we found that compositional changes in colonisation were appropriately reflected by the newly defined combined eco-morphological functional groups. In the combined eco-morphological functional groups, such kind of taxonomical and ecological features can be prevailed which are hidden in guilds or cell size categories separately. Thus these combined eco-morphological functional groups could help to come one step closer to develop a widely used ecological classification in diatom researches.

B-Béres Viktória et al. (2016): Kitaibelia

B-Béres Viktória, Nagy-László Zsolt, T-Krasznai Enikő, Stenger-Kovács Csilla, Barreto Sára, Kiss Gábor, Buczkó Krisztina, Abonyi András

A 2015-ös év algája szavazás jelöltjei = The Algae of the Year 2015 – Candidates of the election

Abstract 

While science-based education is widespread for macroscopic flora and fauna, the microscopic world has received much less attention. In 2015, having the aim of establishing a tradition, the Phycological Forum announced its first “Alga of the Year” in form of an online voting. The three candidates of algae were Didymosphenia geminata, Haematococcus pluvialis and Prymnesium parvum, from which the Haematococcus pluvialis received the overwhelming majority of votes. Introducing the ecological and economical aspects and distribution of the candidate taxa in Hungary, we aimed at to stress that there is a high educational potential of microscopic life. Furthermore, our study draws the attention to the fundamental role of algae in aquatic ecosystems, stressing their importance in maintaining life.

Bolgovics et al. (2016): Hydrobiologia

Bolgovics Ágnes, Ács Éva, Várbíró Gábor, Görgényi Judit, Borics Gábor: Species area relationship (SAR) for benthic diatoms: a study on aquatic islands

Abstract

The question of how species richness depends on the area is one of the most intensively studied subjects in biogeography. Many studies have reported this pattern for terrestrial and macroscopic taxa; however, microscopic and aquatic communities have received much less attention in the literature. The aim of our study was to reveal the relationship between the habitat size and richness of freshwater benthic diatom assemblages. We hypothesized that if the size of studied water bodies covers wide spatial scales, the species-area relationship (SAR) could be described by a sigmoid model. Benthic diatom assemblages were investigated in pools, ponds and lakes of various sizes (10⁻²–10⁸ m²). We demonstrated that although the SAR in the log-log space can be described by a linear model, the linear breakpoint regression provides better fit to data. Using this technique a characteristic small island effect (SIE) could be distinguished. The SIE fell in the range of 10⁻²–10⁴ m². We also demonstrated that species richness of the diatom guilds is remarkably different in the various size ranges of the water bodies. We also demonstrated that the slope of the SAR (z value) is similar to those values that have been reported for other microbial organisms.

Borics et al. (2016): Hydrobiologia

Borics Gábor, Tóthmérész Béla, Várbíró Gábor, Grigorszky István, Czébely Andrea, Görgényi Judit: Functional phytoplankton distribution in hypertrophic systems across water body size

Abstract

the lowland region of the Carpathian basin in a late summer period. It has been demonstrated that lake size has pronounced impact on the morphological and chemical properties of the water bodies, and acting through these variables it shapes the distribution of the various algal groups in the water bodies of different sizes. Changes of the relative abundance of the various algal groups along the spatial scale showed four apparently distinct patterns. We found increasing relative abundance of heterocytic cyanobacteria, dinoflagellates and those taxa which have no capability of active locomotion and are characterised by high sinking rate in the large water bodies. The flagellated algae (Chlamydomonas spp., euglenophytes, Synura spp.) and the tichoplanktonic elements were characteristic for small-sized water bodies. Most of the chrysophytes and several other flagellated taxa showed hump-shaped distribution along the size scale of water bodies. The group of large colonial flagellated chlorophytes, non-heterocytic filamentous cyanobacteria and filamentous chlorophytes occasionally occurred in high relative abundance both in small and large-sized water bodies. Our findings suggest that water body size has pronounced impact on the composition of algal assemblages.

Buczkó (2016): Studia Botanica Hungarica

Krisztina Buczkó: FOREWORD: DIATOM MICROGRAPHS OF THE CARPATHIAN REGION – ICONOGRAPHIA DIATOMOLOGICA CARPATHICA

In the last couple of years – as other fields of photography – microphotography also benefited from the impressive, new advancements of digital technique. Diatom specialists profited from microphotography becoming cheap and easily accessible by making possible the publication of detailed documentation of diatom taxa regardless of size and resolution. However, there are signifi cant diff erences in applying microphotography in diff erent regions, where Hungary plays a pioneering role. As for Hungary, the microphotographs have long history going back to ca 150 years starting with the work of József Pantocsek (1846–1916), a prominent, well-known diatomist of the Carpathian Basin, with more than 1,300 described diatom taxa (Buczkó 2012). In his collection more than 400 microphotographs are stored, the result of his pioneer sea rch for the best ways to document the enormous diversity of diatoms. His experiments in microphotography were fruitful and as a photographer he won awards with his diatom pictures in 1884 on the National Exhibition. However, perhaps the photodocumentation turned out to be too expensive or time-consuming, Pantocsek turned back to drawing his specimens as documentation. Th us, most of his books and papers were exclusively published with tint-drawings (Buczkó 2012). Among the first microphotographers Oszvald Gallik must also be mentioned. He published pictures of diatoms of Lake Balaton, especially taxa belonging to the Cymbella genus (Gallik 1926). However, the delineation of most diatoms remained documented by drawings for decades. In Hungary, the Hungarian Geological Institute could support the high quality scanning and light microscope photodocumentation from the 1960s, till the 1990s, resulting in the unusual situation that the fossil diatom fl ora is quite well documented (Hajós 1986), while the recent diatoms were rather neglected concerning modern illustrations. Moreover, the prominent diatomists of the time focused exclusively on the taxonomy of a genus or group, and microphotographs have been published just of a restricted group, e.g. centric forms in Kiss et al. (2012). A new epoch in the global history of diatom research began in the 1980s, when the most of the newly described freshwater diatom fl ora relied on photographs rather than on drawings, largely due to the work of Krammer and LangeBertalot (e.g. 1986–1991). Aft er these first volumes several richly illustrated books and monographs followed each other: the series of Bibliographia Diatomologica (ed. H. Lange-Bertalot), Iconographia Diatomologica (ed. H. Lange-Bertalot), and the Diatom Monographs, (ed. A. Witkowski). Illustrated checklists of diatoms inhabiting lakes and rivers were still not available, until recently in the Carpathian region. The detailed diatom guide to the sodic lakes of Hungary of Stenger-Kovács and Lengyel (2015) appeared aft er a long gap. Hopefully, we can regard their compilation as the opening volume of a new series that aims to document – based on modern photographic means – the diatom flora of the Carpathians. The present publication – as a new volume of the series – was constituted to be a guide for the diatoms of the Retezat Mountains. We hope that in the forthcoming years more diatom guides will be published of the Carpathian region contributing to the “Iconographia Diatomologica Carpathica” series. A new project entitled “CRYPTIC – Cryptogam’s Traits in the Carpathians” (see at buczko.eu/Cryptic) also supports the realisation of this project (thanks to the National Research, Development and Innovation Offi ce NKFI-6 119208). We are confi dent that the “Iconographia Diatomologica Carpathica” series will provide a complete overview on the diatoms of the Carpathian region, and hopefully, as such, will be a substantial help for any diatomists working in the region or far away. The series will serve as a relevant source of information for non-diatom experts with scientifi c interest in the biogeography or morphological diversity of diatoms. 

Buczkó et al. (2016): Studia Botanica Hungarica

Krisztina Buczkó: Guide to diatoms in mountain lakes in the Retezat Mountains, South Carpathians, Romania

Abstract

Mountain lakes have special importance in the neo- and palaeolimnology. Th e diatom fl ora of mountain regions of Europe has been studied in detail, but less attention was paid to the Romanian part of the Carpathians. Siliceous algae of mountain lakes (1,740–2,122 m a.s.l.) were studied in the Retezat Mts (South Carpathians, Romania). Sediment samples were collected in the deepest points of twenty-three pristine lakes between 2011 and 2014. A total of 152 species and intraspecifi c diatom taxa were found during this study (excluding the representatives of the two most diverse diatom genera Eunotia and Pinnularia). Altogether 140 taxa were listed and nomenclaturally checked from the previously published results. 79 common species and some rarely reported taxa are illustrated by means of light- (LM) and scanning electron microscope (SEM), and 40 other are presented here only with LM images. A partial diatom checklist is presented with 217 items, 80 of them have been recently recorded for the Retezat Mountains. Th is compilation focuses on small celled (< 20 μm) diatoms. Th e main aim is to help the identifi cation to the hardly visible, lightly silicifi cied and recently described forms, instead of repeating the earlier published data. Th is guide consist of a detailed light and scanning electron microscopy documentation of the diatom fl ora, based on 752 LM and 188 SEM pictures. New Humidophila and Staurosira taxa are presented and a new combination is proposed for Achnanthes helvetica var. minor. Th e detailed, illustrated guide hopefully will be a useful manual for ecological and palaeoecological surveys in the future. 

Fuchs et al. (2016): Hydrobiologia

Andrea Fuchs, Géza B. Selmeczy, Peter Kasprzak, Judit Padisák, Peter Casper: Coincidence of sedimentation peaks with diatom blooms, wind, and calcite precipitation measured in high resolution by a multi-trap

Abstract

Organisms and processes in the epilimnion of lakes determine the rate of sedimentation. To investigate the impact of phyto- and zooplankton on the sedimentation rate, we sampled the sedimenting material in Lake Stechlin. Sedimenting matter was collected using a high-resolution multi-trap in three-day intervals during the thermally stratified seasons in 2011 (at 65 m depth) and 2012 (at 20 m depth). Dry weight of the sedimented material was related to chemical, physical, and biological data collected from the water column, as well as to meteorological data. The high-resolution trap showed two mass sedimentation peaks in 2011 and one in 2012. We found that diatom blooms in spring were followed by the highest sedimentation rate in 2011, but not in 2012. The sedimentation rates significantly correlated to low wind speed, followed by a rapid formation of the thermocline, as well as to high calcite concentrations in 2011. Our results suggest that the presence of some aggregation factors like calcite crystal exopolymers or fecal pellets support the sinking process. Furthermore, the high resolution of the trap used here allowed for obtaining precise correlations between sedimentation and the measured parameters indicating relevance of temporal coincidence of multiple environmental variables.

Görgényi et al. (2016): Hydrobiologia

Görgényi J, Boros G, Vitál Z, Mozsár A, Várbíró G, Vasas G, Borics G: The role of filter-feeding Asian carps in algal dispersion

Abstract

The gut contents of filter-feeding fish often contain considerable amounts of viable phytoplankton cells; thus, these animals can act as vectors in the horizontal and vertical transport of algae. In this study, the potential role of the introduced filter-feeding Asian carps (hybrids of silver carp Hypophthalmichthys molitrix and bighead carp H. nobilis) in algal dispersion was studied in the oligo-mesotrophic Lake Balaton (Hungary). We examined the algal composition in the lake water, gut contents (foregut and hindgut), and occasionally in the filtered suspensions collected directly from the gill rakers (filtering apparatus) of fish. Microscopic analyses revealed that the phytoplankton composition of the ingested food differed considerably from what we found in the lake water. Cryptophytes, dinoflagellates, and euglenophytes were observed in both the lake water and foregut samples but were absent in the hindgut samples. However, in the cultured hindgut samples, we found viable cells of several phytoplankton taxa (e.g., diatoms, blue-greens, desmids, volvocalean and chlorococcalean green algae), which managed to survive the physical and chemical digestion. These results imply that the presence of these filter-feeding fish can alter the phytoplankton species composition and promote the dominance of taxa that are able to resist digestion.

Hu et al. (2016): Hydrobiologia

Ren Hu, Qiuhua Li, Bo-Ping Han, Luigi Naselli-Flores, Judit Padisak, Nico Salmaso: Tracking management-related water quality alterations by phytoplankton assemblages in a tropical reservoir

Abstract

Water quality improvement and suppression of cyanobacterial blooms were planned in a eutrophic reservoir in southern China through ecological engineering measures from 2006 to 2011. This consisted in (i) a hydraulic resetting of inflows and outflows to increase the distance between inlet and outlet and the water residence time in the reservoir, and in (ii) the installation of floating frames hosting wetland vegetation to promote an alteration in phytoplankton composition. The environmental changes were therefore followed through the analysis of biotic responses in phytoplankton assemblages. Ecological engineering was effective in reducing phytoplankton total biomass, in re-establishing more diversified phytoplankton assemblages and in avoiding cyanobacterial blooms. These changes may be considered as an improvement of the reservoir water quality. However, trophic state parameters and the dynamics of dominant species were not sensitive enough in describing the environmental changes that had occurred when the eco-engineering measures were implemented. These were more effectively tracked by the dynamics followed by phytoplankton Morpho-Functional-Groups and by their classification based on Competitors, Stress tolerants and Ruderals strategies. Although providing immediate positive effects, the eco-engineering was temporally limited, highlighting the importance of constant management in the context of long-term oriented remediation techniques.

Leese et al. (2016): Research Ideas and Outcomes (Rio) 2

Leese F et al.: DNAqua-Net: Developing new genetic tools for bioassessment and monitoring of aquatic ecosystems in Europe

Abstract

The protection, preservation and restoration of aquatic ecosystems and their functions are of global importance. For European states it became legally binding mainly through the EU-Water Framework Directive (WFD). In order to assess the ecological status of a given water body, aquatic biodiversity data are obtained and compared to a reference water body. The quantified mismatch obtained determines the extent of potential management actions. The current approach to biodiversity assessment is based on morpho-taxonomy. This approach has many drawbacks such as being time consuming, limited in temporal and spatial resolution, and error-prone due to the varying individual taxonomic expertise of the analysts. Novel genomic tools can overcome many of the aforementioned problems and could complement or even replace traditional bioassessment. Yet, a plethora of approaches are independently developed in different institutions, thereby hampering any concerted routine application. The goal of this Action is to nucleate a group of researchers across disciplines with the task to identify gold-standard genomic tools and novel eco-genomic indices for routine application in biodiversity assessments of European fresh- and marine water bodies. Furthermore, DNAqua-Net will provide a platform for training of the next generation of European researchers preparing them for the new technologies. Jointly with water managers, politicians, and other stakeholders, the group will develop a conceptual framework for the standard application of eco-genomic tools as part of legally binding assessments.

Lengyel et al. (2016): Hydrobiologia

Edina Lengyel, Judit Padisák, Éva Hajnal, Beáta Szabó, Attila Pellinger, Csilla Stenger-Kovács: Application of benthic diatoms to assess efficiency of conservation management: a case study on the example of three reconstructed soda pans, Hungary

Abstract

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.

Müller et al. (2016): Ecological Indicators

Müller, F., Bergmann, M., Dannowski, R., Dippner, J. W., Gnauck, A., Haase, P.,  Jochimsen, M. C.,  Kasprzak, P., Kröncke, I., Kümmerlin, R., Küster, M., Lischeid, G.,  Meesenburg,H.,  Merz, C. ,  Millat, G., Müller, J.,  Padisák, J., Schimming, C.G., Schubert, H., Schult, M.,  Selmeczy, G.,  Shatwell, T.,  Stoll, S.,  Schwabe, M.,  Soltwedel, T.,  Straileg, D.,  Theuerkauf, M..  & Küster, M.: Assessing resilience in long-term ecological data sets.

Abstract

In this paper the concept of resilience is discussed on the base of 13 case studies from the German branch of the International Long-Term Ecological Research Program. In the introduction the resilience approach is presented as one possibility to describe ecosystem dynamics. The relations with the concepts of adaptability and ecological integrity are discussed and the research questions are formulated. The focal research objectives are related to the conditions of resilient behaviour of ecosystems, the role of spatio-temporal scales, the differences between short- or long-term dynamics, the basic methodological requirements to exactly define resilience, the role of the reference state and indicators and the suitability of resilience as a management concept. The main part of the paper consists of 13 small case study descriptions, which demonstrate phase transitions and resilient dynamics of several terrestrial and aquatic ecosystems at different time scales. In the discussion, some problems arising from the interpretation of the time series are highlighted and discussed. The topics of discussion are the conceptual challenges of the resilience approach, methodological problems, the role of indicator selection, the complex interactions between different disturbances, the significance of time scales and a comparison of the case studies. The article ends with a conclusion which focuses on the demand to link resilience with adaptability, in order to support the long-term dynamics of ecosystem development.

Naselli-Flores & Padisák (2016): Hydrobiologia

Luigi Naselli-Flores, Judit Padisák: Blowing in the wind: how many roads can a phytoplanktont walk down? A synthesis on phytoplankton biogeography and spatial processes

Abstract

The selected theme of the 17th Workshop of the International Association for Phytoplankton Taxonomy and Ecology (IAP), “Biogeography and Spatial Patterns of Biodiversity of Freshwater Phytoplankton,” offered the opportunity to explore one neglected aspect of phytoplankton ecology: the distribution of species in the geographic space. This paper summarizes the outcomes of 20 selected contributions among those presented at the workshop. The articles report the results from studies carried out in five continents (only Oceania is not represented) and on a wide array of aquatic ecosystems (deep and shallow natural lakes, man-made lakes, temporary and permanent ponds, rivers). The topics analyzed by the contributors are related to Island Biogeography paradigms, dispersal vectors, survival strategies, environmental filters, dispersal distances, vertical and horizontal spatial variability of phytoplankton between and within water bodies, and of course, invasive algae. The overall analysis of the results presented clearly demonstrates that, as for many others organisms, there are “rules” governing freshwater phytoplankton spatial patterns and that these organisms also have a true biogeography, as nowadays is quite evident for several other groups in the same range of size. We can definitively conclude that the statement “Everything is everywhere” is obsolete, even though human activities tend to homogenize species distribution in the biosphere.

Padisák et al. (2016): Hydrobiologia

Judit Padisák, Gábor Vasas, Gábor Borics: Phycogeography of freshwater phytoplankton: traditional knowledge and new molecular tools

Abstract

“Everything is everywhere, but environments selects.” Is this true? The cosmopolitan nature of algae, including phytoplankton, has been highlighted in many textbooks and burnt into the minds of biologists during their studies. However, the accumulating knowledge on the occurrence of individual phytoplankton species in habitats where they have not been seen before, reports on invasive phytoplankton species, and the increasing number of papers with phylogenetic trees and tracing secondary metabolites, especially cyanotoxins, contradict. Phytoplankton species, with rare exceptions, are neither cosmopolitan, nor ubiquists. In this review paper, we provide an overview of the basic patterns and the processes relevant for biogeography of freshwater phytoplankton. The following topics are considered: dispersal agents and distances; survival strategies of species; geographic distribution of different types; patterns of invasions; tools of molecular genetics; and metabolomics to explore dispersal patterns, island biogeography, and associated species–area relationships for algae.

Pál et al. (2016): Holocene

Pál I, Magyari E K, Braun M, Vincze I, Pálfy J, Molnár M, Finsinger W, Buczkó K: Small-scale moisture availability increase during the 8.2-ka climatic event inferred from biotic proxy records in the South Carpathians (SE Romania)

Abstract

In this paper, we present high-resolution early Holocene pollen, plant macrofossil, charcoal, diatom, biogenic silica, and loss-on-ignition records from a mountain lake in the South Carpathians in order to reveal ecosystem response to the 8.2-ka climatic oscillation. We found significant changes both in terrestrial vegetation and lake diatom assemblages in the northern slope of the Retezat Mts between c. 8300 and 8000 cal. yr BP. Rapid changes in relative frequencies and pollen accumulation rates of the major deciduous pollen types associated with peaks in microcharcoal accumulation rates suggested that vegetation disturbance mainly took place in the mixed-deciduous forest zone, where woodland fires partially destroyed the populations of Fraxinus excelsior, Quercus, and Corylus avellana and facilitated the establishment of Carpinus betulus in the forest openings. The diatom record furthermore showed the spread of a planktonic diatom species, Aulacoseira valida, at 8150 cal. yr BP, coincidently with a short-lived expansion of C. betulus. Since diatom blooms mainly occur in spring in the Retezat Mts, increased spring water depth and increased water turbulence were inferred from these data. The expansion of C. betulus against F. excelsior and C. avellana at the same time suggested a modest increase in available moisture during the growing season. Taken together, these data imply that during the 8.2-ka event, winter and spring season available moisture increased, while summers were characterized by alternating moist/cool and dry/warm conditions.

Selmeczy et al. (2016): Hydrobiologia

Géza B. Selmeczy, Kálmán Tapolczai, Peter Casper, Lothar Krienitz, Judit Padisák: Spatial- and niche segregation of DCM-forming cyanobacteria in Lake Stechlin (Germany)

Abstract

At low trophic state, stable stratified water columns may provide favorable conditions for adapted phytoplankton species to form deep chlorophyll maxima (DCM). Such maxima occur regularly in Lake Stechlin, mainly contributed by the cyanobacterial species Cyanobium sp. and occasionally by Planktothrix rubescens. In the early twenty-first century, a rapid invasion by nostocalean cyanobacteria occurred in the lake and a number of Dolichospermum species together with Aphanizomenon flos-aquae appeared. As revealed by both microscopic and fluorimetric methods, during the summer stratification of 2013, a multispecific DCM was formed by Cyanobium, Planktothrix rubescens, and A. flos-aquae, however with spatial segregation. Planktothrix occurred in the upper hypolimnion, Aphanizomenon and Cyanobium dominated in the metalimnetic layer. Coexistence of these three cyanoprokaryota is possibly the consequence of different environmental factors limiting them (light, availability of N and P). This study represents a rare case when spatial niche segregation of phytoplankton species occurs in close to equilibrium conditions. DCM formed by Aphanizomenon and Cyanobium was detected by the fluoroprobe; Planktothrix with its different pigment compositions remained largely hidden. Our results indicate the necessity of parallel microscopic investigations and the need of careful calibration when fluorimetric methods are used for detecting cyanobacterial populations.

Stenger-Kovács et al. (2016): Ecological Indicators

Csilla Stenger-Kovács, Éva Hajnal, Edina Lengyel, K. Buczkó, Judit Padisák: A test of traditional diversity measures and taxonomic distinctness indices on benthic diatoms of soda pans in the Carpathian basin

Abstract

Saline lakes are threatened all over the world and their conservation has been a key issue. Various diversity indices are available for ecological status assessments, however, with poorly explored relevance and applicability in saline, alkaline pans. Therefore, traditional diversity measures (species richness and Shannon diversity) and taxonomic distinctness indices (Average [AvTD] and Variance of Taxonomic Distinctness [VarTD]) were tested in more than 100 sampling sites of 39 soda pans in Central-Europe to find sufficient indicators of the ecological condition and simultaneously to facilitate their preservation according to the modern conservation practices. Results of the analyses showed that healthy soda pan ecosystems with high level of natural stress and reduced habitat heterogeneity are characterized by low diversity diatom assemblages. In soda pans where the stress can be extremely high from natural reasons, oligopoly of closely related species can develop: the average taxonomic distinctness appeared between genus and family level. The non-DNA-sequence based phylogenetic diversity measures (AvTD and VarTD), were generally sensitive to the trophic state of the lakes, in contrast to traditional diversity metrics, which were unequivocally indicative for the special physical and chemical parameters (e.g. conductivity, pH) of the soda pans. In some cases, when the response of the diversity measures for a given environmental variable (pH, temperature) overlapped, the AvTD was found to be a more precise indicator of the environmental changes (pH) than traditional ones. The decreasing tendency of the AvTD along the intensified natural impact may be explained by the long available time for the species to adapt to these special environments.

Tapolczai et al. (2016): Hydrobiologia

Kálmán Tapolczai, Agnès Bouchez, Csilla Stenger-Kovács, Judit Padisák, Frédéric Rimet: Trait-based ecological classifications for benthic algae: review and perspectives

Abstract

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.

Török et al. (2016): Functional Ecology

Török P, T-Krasznai E, B-Béres V, Bácsi I, Borics G, Tóthmérész B: Functional diversity supports the biomass-diversity humped-back relationship in phytoplankton assemblages

Summary

1. Modelling the relationship between biomass and diversity in phytoplankton assemblages provides new insights into the mechanisms responsible for the coexistence of species, even in terrestrial ecosystems.
2. We tested the biomass–diversity relationship in lake phytoplankton along a wide biomass gradient using functional species groups. We hypothesized that changes in the taxonomic diversity of the phytoplankton along a biomass gradient are associated with altered functional diversity.
3. For the analyses, in total 768 samples were collected from 30 oxbows, reservoirs and lakes in the Hungarian Lowland Region and analysed between 1992 and 2002.
4. We found that the diversity and also the number of functional species groups showed a humped-back curve similar to the species richness. The changes in functional group composition act as a good proxy for phytoplankton species responses. We found that the peak of the number of strategy groups and their Shannon diversity was at a much lower biomass than that of species richness.
5. We revealed the fine-scale effects of increasing the dominance of respective species or species groups with increasing biomass. This increase was well reflected by the changes in the functional characteristics: first, the species evenness; then, the Shannon diversity; and finally, the species richness started to decrease with increasing biomass.
6. Cyanoprokaryota were positively correlated with increasing biomass and negatively with the increase in species richness; thus, the high increase both in their abundance and biomass can be responsible for the abruptly decreasing part of the humped-back curve.
7. We detected a humped-back curve between biomass and diversity, where the peak compared to terrestrial plant communities tended to be towards high biomass scores, that is, >60% instead of the 20–60% of the biomass range typical for terrestrial plant communities. Marked differences in the structural and dynamic features of phytoplankton assemblages and terrestrial plant communities are likely responsible for this difference.

Williams & Buczkó (2016): Phytotaxa

David Mervyn Williams, Kristina Buczkó: Fragilariforma Hajósiae: re-description and revision of Pantocsek’s species Diatoma fossile (Bacillariophyta)

Abstract

Fragilariforma Hajósiae is re-described from Pantocsek’s specimens of Diatoma fossile; these specimens are from Deménd (Demandice, Slovakia). Nomenclatural issues are examined and clarified as the name Fragilaria fossilis has previously been invalidly used by Hajós (1973a) and the combination Fragilariforma fossilis (Pant.) Tanaka unavailable thus making it necessary to create a new name to effect the transfer of Pantocsek’s Diatoma fossile to Fragilariforma.

Yang et al. (2016): Hydrobiologia

Yang Yang, Kurt Pettersson, Judit Padisák: Repetitive baselines of phytoplankton succession in an unstably stratified temperate lake (Lake Erken, Sweden): a long-term analysis

Abstract

The seasonal development of phytoplankton is a sequence of consecutive events with waxes and wanes of biomass and compositional shifts. This study analyzed 16 years data in Lake Erken, Sweden and revealed four baselines of phytoplankton succession with their underlying drivers. Results showed that there were two diatom-dominated phases annually. The vernal community was dominated by centric diatoms larger than 15 µm (functional groups B and C) which were fast-growing diatoms being highly efficient in the use of nutrients. The autumn community was comprised mainly meroplanktonic mixing-dependent Aulacoseira granulata and Fragilaria sp. (MP and P) or/and large centric diatoms (B). Between the two mixing-phases with diatoms, a Gloeotrichia echinulata (H2) bloom occurred due to its preference for a stratified water column with elevated water temperatures and high light availability. The summer stratification in Lake Erken was weak and short, thus, favoring meroplanktonic diatoms to peak once the lake turned over in early autumn. Lake Erken represents an intermediate case between a highly mixed polymictic lake and a lake with strong summer stratification, where the observed stratification patterns allowed the development of an autumn diatom phase similar, by extent, to the vernal one and mainly dominated by meroplanktonic diatoms.

Yang et al. (2016): Hydrobiologia 

Yang Yang, Csilla Stenger-Kovács, Judit Padisák, Kurt Pettersson: Effects of winter severity on spring phytoplankton development in a temperate lake (Lake Erken, Sweden)

Abstract

Phytoplankton seasonal succession has been linked to a variety of serial environmental changes, especially weather- and climate-induced physical forcing. This study compared spring phytoplankton dynamics after winters of different severity (cold, normal, and warm) in Lake Erken, Sweden. The spring diatom bloom was dominated by different functional groups: group A (centric diatoms 5–10 μm) after cold winters, B (centric diatoms >15 μm) after normal winters, and P (Aulacoseira granulata, Fragilaria crotonensis) after warm winters. Our results suggest that weather-related processes were the primary external drivers accounting for differences in spring phytoplankton dynamics in Lake Erken. Spring phytoplankton are influenced by overwintering species from the last autumn that can initiate the following spring bloom. Average taxonomic distinctness of the spring community was assessed using a new biodiversity measurement that incorporates taxonomic relatedness information. This value was lower than expected after warm and cold winters, which had winter air temperature 1°C deviation from an average value calculated over 21 years. Such winters increased the level of disturbance or stress to the lake, resulting in a spring with less diverse phytoplankton by narrowing the niche for species with various ecological requirements.

Bácsi et al. (2015): Ecotoxicology

Bácsi I, Gonda S, B-Béres V, Novák Z, Nagy SA, Vasas G: Alterations of phytoplankton assemblages treated with chlorinated hydrocarbons: Effects of dominant species sensitivity and initial diversity

Abstract

Changes in composition of phytoplankton assemblages due to short-chained chlorinated hydrocarbons (tetrachloroethane, tetrachloroethylene and trichloroethylene) were studied in microcosm experiments with different initial diversities. Diversity decreased further during treatments in the less diverse 2011 summer assemblages, dominated by the euglenid Trachelomonas volvocinopsis (its relative abundance was nearly 70 %). Diversity did not change significantly during treatments in the more diverse 2012 summer assemblages, dominated by cryptomonads (their relative abundance was 40 %). The dominant Trachelomonas volvocinopsis in 2011, due to its insensitivity to the treatment and presumably high competition skills, filled released habitats occurring when sensitive species were not detectable any more. In contrast, cryptomonads were extremely sensitive to the treatments, their abundance decreased under detection limit in the treated assemblages, regardless of diversity conditions. Our results showed that population dynamics of dominant species determine the response to the contamination of the entire community, if these species display high resistance or resilience. If the dominant species was highly sensitive and recovered slowly, compensatory growth of rare species maintained high levels of ecosystem performance.

Bácsi et al. (2015): International Journal of Environmental Science and Technology

Bácsi I, Novák Z, Jánószky M, B-Béres V, Grigorszky I, Nagy SA: The sensitivity of two Monoraphidium species to zinc - their possible future role in bioremediation

Abstract

Effects of zinc on growth, cell morphology, oxidative stress responses and zinc removal activity of two common phytoplankton species, Monoraphidium pusillum (Printz) Komárková-Legnerová and Monoraphidium griffithii (Berkeley) Komárková-Legnerová were investigated at a concentration range of 0.2–160 mg l⁻¹ zinc. Cell densities and chlorophyll content decreased compared with controls in cultures of both species, effective concentrations causing 50 % growth inhibition within 72 h on the basis of cell numbers were 33.69 and 25.63 mg l⁻¹ zinc for M. pusillum and M. griffithii, respectively. Changes in cell morphology and elevated lipid peroxidation levels appeared in zinc-treated cultures of both species, but only at higher (>10 mg l⁻¹) zinc concentrations. The most effective zinc removal appeared at 20 and 10 mg l⁻¹ zinc concentration for M. pusillum and M. griffithii, respectively. Removed zinc is mainly bound on the cell surface in the case of both species. This study provides new data for the zinc tolerance and zinc removal ability of the green algae M. pusillum and M. griffithii and shows that green algal species common in surface waters could have zinc tolerance and zinc-binding abilities, which makes them feasible in treatment of waters contaminated with 10–20 mg l⁻¹ zinc.

B-Béres et al. (2015): Marine Drugs 

Viktória B-Béres, Gábor Vasas, Dalma Dobronoki, Sándor Gonda, Sándor Alex Nagy, István Bácsi: Effects of Cylindrospermopsin Producing Cyanobacterium and Its Crude Extracts on a Benthic Green Alga - Competition or Allelopathy?

Abstract

Cylindrospermopsin (CYN) is a toxic secondary metabolite produced by filamentous cyanobacteria which could work as an allelopathic substance, although its ecological role in cyanobacterial-algal assemblages is mostly unclear. The competition between the CYN-producing cyanobacterium Chrysosporum (Aphanizomenon) ovalisporum, and the benthic green alga Chlorococcum sp. was investigated in mixed cultures, and the effects of CYN-containing cyanobacterial crude extract on Chlorococcum sp. were tested by treatments with crude extracts containing total cell debris, and with cell debris free crude extracts, modelling the collapse of a cyanobacterial water bloom. The growth inhibition of Chlorococcum sp. increased with the increasing ratio of the cyanobacterium in mixed cultures (inhibition ranged from 26% to 87% compared to control). Interestingly, inhibition of the cyanobacterium growth also occurred in mixed cultures, and it was more pronounced than it was expected. The inhibitory effects of cyanobacterial crude extracts on Chlorococcum cultures were concentration-dependent. The presence of C. ovalisporum in mixed cultures did not cause significant differences in nutrient content compared to Chlorococcum control culture, so the growth inhibition of the green alga could be linked to the presence of CYN and/or other bioactive compounds.

B-Béres et al. (2015): Acta Botanica Croatica

B-Béres V, Bácsi I, T-Krasznai E, Kókai Zs, Buczkó K: First report of Navicula jakovljevicii Hustedt (Bacillariophyta) from Hungary: distribution, comparative morphology and a related species

Abstract

In Hungary Navicula jakovljevicii was firstly recorded in biofilm of Elodea nuttallii in 2005 in an oxbow of the catchment area of the River Danube. Subsequently, in 2006, N. jakovljevicii was also found in the same oxbow on reed stems as well. In the following years it appeared in another oxbow, suggesting an expanding distribution in the tributaries of the Danube in Hungary. The Hungarian population can be characterised as having mixed morphological features in comparison with other known N. jakovljevicii populations of Europe. When the morphological study was expanded, a similar, but 'giant form' was detect ed in fossil material. We found similarities and a possible connection between N. jakovljevicii and Navicula lucida, a diatom taxon described from a Neogene deposit in the Carpathian Basin. Despite the morphological similarities in the shape, apices, striae pattern and raphe structure of these two species, there are significant differences in valve dimensions: the valves of N. lucida are larger and more heavily silicified than N. jakovljevicii.

Bolgovics et al. (2015): Acta Botanica Croatica 

Bolgovics Á, Ács É, Várbíró G, Kiss KT, Lukács BA, Borics G: Diatom composition of the rheoplankton in a rhithral river system

Abstract

Diatom composition of the rheoplankton (phytoplankton) in the Sajó-Hernád river system (Slovakia and Hungary) was studied. Forty two sample sites were designated on the watershed from source to mouth of the two rivers and their tributaries. Samples were taken in July 2012. Altogether, 258 diatom taxa were identified. The microflora was dominated by tychoplanktonic elements. According to the relative abundance of the occurring taxa, four groups could be distinguished. Differentiation of these groups was confirmed by differences in the habitat characteristics, viz. altitude, width of watercourse, macrophyte coverage and river bed material. Diversity of diatom taxa in the phytoplankton was also studied. A positive relationship was found between the macrophyte coverage and the Simpson and the Shannon indices. In contrast, a negative relationship was shown between the macrophyte coverage and Berger-Parker diversity, in which metric the role of the dominant taxa is emphasized. Although the phytoplankton in rhithral rivers is influenced by stochastic events, our results reveal that geographical and hydromorphological characteristics of the rivers and coverage of macrophytes can also play role in shaping the composition and diversity of the phytoplankton.

Borics et al. (2015): Inland Waters

Gábor Borics, András Abonyi, Gábor Várbíró, Judit Padisák, Enikő T-Krasznai: Lake stratification in the Carpathian basin and its interesting biological consequences

Abstract

Stratification of small temperate lakes of the Carpathian basin was studied. Values of Schmidt stability and Lake Number indicated stable summer stratification. Depending on their depth and wind shelter, the lakes could be characterized by various stratification patterns. A near-linear stratification was observed in the Malom Tisza oxbow where in summer during midday the whole water column belonged to the metalimnion. Mixing of the upper water layer was generated by nocturnal cooling. Stable stratification had pronounced consequences for the vertical distribution of chemical variables and phytoplankton. Concentration of sestonic chlorophyll showed bimodal distribution produced by algae in the upper and purple bacteria in the deeper layers. These results revealed that processes and phenomena associated with deep stratified lakes can be observed in shallow basins.

Buczkó et al. (2015): Studia Botanica Hungarica

Buczkó, K., Wojtal, A., Beszteri, B. & Magyari, E.: Morphology and distribution of Navicula schmassmannii and its transfer to genus Humidophila

Abstract 

A small diatom with a peculiar shape is often identified as Navicula schmassmannii in samples collected from alpine lakes and the Arctic region. Due to its characteristic outline, it is relatively well-identifiable, but scanning electron microscope (SEM) confirmation is essential for proving species identity. This species likely has a palaeoecological indicator value of warming climate in mountain lakes, although it is generally a minor component of the diatom assemblages. Here we re-investigate its type material to clarify its identity and taxonomic position. We provide an emended description based on SEM observation, including new information on girdle morphology. Furthermore, another population of N. schmassmannii was studied. Detailed morphological observations using light microscope (LM) and SEM were done on specimens from a sediment core obtained from Lake Brazi in the Southern Carpathian Mountains. Late-glacial and early Holocene populations of the diatom resembling N. schmassmannii showed high morphological variability in comparison with the type material. On the basis of details of type material and the different morphotypes from Lake Brazi, the transfer of N. schmassmannii Hustedt to the genus Humidophila is proposed as H. schmassmannii (Hustedt) Buczkó et Wojtal.

Buczkó et al. (2015): Phytotaxa

Krisztina Buczkó, Nadja Ognjanova-Rumenova, Agata Z. Wojtal, Csilla Stenger-Kovács: Ultrastructure and taxonomic position of Cymbella latestriata Pantocsek (Bacillariophyta)

Abstract

A rare Neogene species, Cymbella latestriata, was studied by light and scanning electron microscopy. Cymbella latestriata was found to have apical pore fields on both apices, although these are simple, very small. Because of the presence of apical pore fields APF the transfer of this species to the genus Cymbopleura is not justified as previously was suggested by Krammer. Thus, the study confirms Pantocsek’s original assignment of the taxon as Cymbella latestriata.

Duleba et al. (2015): Diatom Research

Duleba, M., Kiss, K. T., Földi, A., Kovács, J., Borojević, K. K., Molnár, L. F., Plenković-Moraj, A.,  Pohner, Zs., Solak, C.N., Tóth, B. & Ács, É.: Morphological and genetic variability of assemblages of Cyclotella ocellata Pantocsek/C. comensis Grunow complex (Bacillariophyta, Thalassiosirales).

Abstract

Centric diatom taxa in the Cyclotella ocellata and C. comensis complexes show high morphological variability and often apparently continuous morphological transitions. In this study, we investigated natural assemblages of the C. ocellata/C. comensis complex from Hungarian and Croatian lakes and from Turkish streams using morphological and molecular methods. The studied assemblages contained cells with morphologies resembling C. ocellata as well as other, closely related, species: C. comensis, C. pseudocomensis, C. costei, and C. trichnoidea. The goal of our paper was to assess whether the observed morphological differences were due to intraspecific variability or suggest the existence of several, putatively distinct species.

Ten morphometric characters were measured, which, either individually, or in pairs, did not differentiate the nominal taxa in our assemblages. However, multivariate discriminant analysis has revealed a group including C. ocellata and C. trichonidea morphologies could be separated from another containing C. comensis, C. pseudocomensis and C. costei.

A nuclear (18S rDNA) and a chloroplast (rbcL) gene were amplified and partially sequenced from environmental DNA or from isolated cells. The sequences showed little variability among the assemblages and nominal species. Although general congruence of molecular and morphometric separation supports the species level separation of C. ocellata/trichonidea from the probably conspecific C. comensis/pseudocomensis/costei, sequence divergences between the groups are in the same range as within them, so that a conspecificity of all four taxa cannot be unequivocally excluded.

Kókai et al. (2015): Acta Botanica Croatica 

Kókai Zs, Bácsi I, Török P, Buczkó K, T-Krasznai E, Balogh Cs, Tóthmérész B, B-Béres V: Halophilic diatom taxa are sensitive indicators of even short term changes in lowland lotic systems

Abstract

The occurrence and spread of halophilic diatom taxa in freshwater lotic ecosystems are influenced both by natural processes and anthropogenic pollution. Diatom assemblages were regularly monitored in lowland lotic systems in Hungary (Central Europe) during the unusually dry year of 2012. Highly pronounced changes in diatom composition were observed from spring to autumn. Halophilic taxa (especially Nitzschia sensu lato species) appeared in the dry autumn. In addition, the total relative abundances of halophilic species also increased up to autumn. Abundance of Nitzschia cf. lorenziana and Nitzschia tryblionella showed a positive correlation with chloride and phosphate concentration, while that of other taxa like Tryblionella apiculata or Tryblionella calida showed a positive correlation with the concentration of nitrate. Our findings clearly demonstrated that these halophilic and mesohalophilic diatom taxa were sensitive indicators of even short-term changes in lowland lotic ecosystems, such as the increasing salt concentration from spring to autumn caused by the lack of rainfall and/or environmental loads.

Kövér et al. (2015): Acta Botanica Croatica

Csilla Kövér, János Korponai, Sándor Harangi, Krisztina Buczkó: A new European record of Diadesmis fukushimae and its transference to Humidophila genus (Bacillariophyta)

Abstract

Diadesmis fukushimae, a rare oligotraphenic diatom, was found in some high mountain lakes of Romania. Its occurrence in the Parâng and Retezat Mountains is the second European record of the species. To date D. fukushimae has been known only from the type locality (Shenandoah National Park, Virginia, USA) and from a spring (Grotta Guernica, Dolomiti Bellunesi National Park (south-eastern Alps, Italy). Investigation by scanning electron microscopy showed that this species should be transferred to the recently established genus Humidophila. A new combination is proposed, Humidophila fukushimae. The morphological details of the European population are also presented.

Lengyel et al. (2015): Aquatic Ecology

Edina Lengyel, Attila W. Kovács, Judit Padisák, Csilla Stenger-Kovács: Photosynthetic characteristics of the benthic diatom species Nitzschia frustulum (Kützing) Grunow isolated from a soda pan along temperature-, sulfate- and chloride gradients

Abstract

The Carpathian Basin hosts a number of small, shallow, saline, alkaline ponds. As being endorheic basins, they are highly threatened by the climate change and response of biota to changing climate has been largely unexplored. We investigated the effects of salinity changes on the photosynthetic activity of Nitzschia frustulum, which is one of the main dominant taxa of the saline lakes in the Fertő-Hanság Region of the Carpathian Basin. The photosynthetic activity of the species was measured along temperature (5, 10, 15, 20, 25, 30, 35, 40 °C), light (0–8–35–70–110–200–400–800–1200 µmol m⁻² s⁻¹), SO₄²⁻ (0–50–600–1200–2400–3600–4800 mg L⁻¹) and Cl⁻ (0–36–437.5–875–1750–3500–5250 mg L⁻¹) gradients under laboratory conditions in photosynthetron. The conductivity optimal of N. frustulum was around 5600 µS cm⁻¹ with wide salinity tolerance. The species preferred the HCO₃⁻–SO₄²⁻-type waters since its photosynthetic activity (3.62 mg C mg Chl-a⁻¹ h⁻¹) was more than twice higher than in HCO₃⁻–Cl⁻-type media. Its photosynthesis saturated at very low-light intensity, and photoinhibition was not observed during the experiments. The maximal photosynthesis was measured at 28–29 °C. However, above 30 °C, the decline of photosynthesis of N. frustulum can be forecasted.

Lengyel et al. (2015): Hydrobiologia

Edina Lengyel, Judit Padisák, Csilla Stenger-Kovács: Establishment of equilibrium states and effect of disturbances on benthic diatom assemblages of the Torna-stream, Hungary

Abstract

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, Navicula gregaria, 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.

Ognjanova-Rumenova et al. (2015): Phytotaxa

Ognjanova-Rumenova N, Buczkó K, Wojtal A Z, Jahn J: Staurosirella rhombus (Ehrenberg), Ognjanova-Rumenova, Buczkó, Wojtal & R. Jahn, comb. nov.—Typification, morphology and biostratigraphic significance

Abstract

A new combination Staurosirella rhombus (Ehrenberg), comb. nov., is based of Fragilaria rhombus. Using light and scanning electron microscopy, the type material from Jastrabá, Slovak Republic was studied. The taxonomic description and typification was done on the basis of the original line drawings, mica preparations and on raw materials, which are housed in the Ehrenberg Collection, Museum für Naturkunde, Humboldt Universität zu Berlin (BHUPM). Comments are presented regarding possible synonyms, described for the Neogene sediments in the realm of Central Slovakia.

Salmaso et al. (2015): Freshwater Biology

Nico Salmaso, Luigi Naselli-Flores, Judit Padisák: Functional classifications and their application in phytoplankton ecology

Summary

1. Ecologists often group organisms based on similar biological traits or on taxonomic criteria. However, the use of taxonomy in ecology has many drawbacks because taxa may include species with very different ecological adaptations. Further, similar characters may evolve independently in different lineages.

2. In this review, we examine the main criteria that have been used in the identification of nine modes of classifying phytoplankton non-taxonomically. These approaches are based purely on morphological and/or structural traits, or on more complex combinations including physiological and ecological features.

3. Different functional approaches have proved able to explain some fraction of the variance observed in the spatial and temporal distribution patterns of algal assemblages, although their effectiveness varies greatly, depending on the number and characteristics of functional traits used. The attribution of functional traits to single species or broad groups of species has allowed a few classifications (e.g. Functional Groups, FG) to be used in the assessment of ecological status.

4. We stress that the misuse of functional classifications (by applying them under conditions other than those intended) can have serious consequences for interpreting ecological processes. Assigning functional traits or groups cannot be considered a surrogate for the knowledge of species or ecotypes, and the use of specific traits must always be justified and circumscribed within the limits of ecological questions and hypotheses.

5. An important future challenge will be to integrate advances in molecular genetics, metabolomics and physiology with more conventional traits; this will form the basis of the next generation of functional classifications.

Stenger-Kovács & Lengyel (2015): Studia Botanica Hungarica

Csilla Stenger-Kovács, Edina Lengyel: Taxonomical and distribution guide of diatoms in soda pans of Central Europe

Abstract

The 93 most characteristic and dominant diatom taxa (including varieties and forms) of soda pans are presented in this study with detailed information on their distribution. The taxonomical position of five taxa is still unclear. Altogether 1257 light and 180 scanning electron microscopic photos are shown from cleaned valves and frustules as well as from living cells (cultures isolated from these lakes).

Tapolczai et al. (2015): Hydrobiologia

Kálmán Tapolczai, Orlane Anneville, Judit Padisák, Nico Salmaso, Giuseppe Morabito, Tamar Zohary, Rémy D. Tadonléké, Frédéric Rimet: Occurrence and mass development of Mougeotia spp. (Zygnemataceae) in large, deep lakes

Abstract

Over the last decades, mass developments by the filamentous conjugating green alga Mougeotia have been followed in three large peri-alpine lakes (Lake Geneva, Lake Garda, Lake Maggiore) and in the sub-tropical Lake Kinneret. The aim of this study is to highlight annual and interannual patterns of Mougeotia biomass in the studied lakes and select key environmental parameters that may favour and maintain its mass development. Our results confirm former studies that planktic Mougeotia favours meso-oligotrophic conditions and becomes dominant when annual mean total phosphorus concentrations in the epilimnion fall below 20 µg l⁻¹. This triggering factor has effect with interactions of other environmental circumstances such as the water column stability. Physiological and morphological features of the taxon make it a successful competitor under stratified conditions. Results also showed that in three out of the four studied lakes, the annual peak was higher when the annual population development started earlier. Focusing on Lake Geneva, depth and strength of the thermocline, as well as wind speed in the beginning of summer that can cause nutrient replenishment and mix the epilimnion are key factors in the blooming of the taxon.

Vitál et al. (2015): Fundamental and Applied Limnology

Vitál Z, Specziár A, Mozsár A, Takács P, Borics G, Görgényi J, G -Tóth L, Nagy SA, Boros G: Applicability of gill raker filtrates and foregut contents in the diet assessment of filter-feeding Asian carps

Abstract

Reliable estimation of the diet composition of filter-feeding Asian carps is essential to evaluate their effects on ecosystem functioning. In previous studies, the diet composition of these fishes was primarily determined based on the analysis of foregut contents. To assess the reliability of foregut content analysis in diet assessments, these were compared with gill raker filtrate analyses. Gill raker filtrates were found to be more reliable than foregut contents for determining food composition due to higher amounts of sample, significantly higher numbers of identifiable taxa (including both phytoplankton and zooplankton), and considerably higher numbers of intact planktonic individuals. The present findings indicate that diet composition analyses based on foregut samples alone are likely to underestimate the number of individuals and the biomass of planktonic species which are less resistant to digestive processes.

Wojtal et al. (2015): Phytotaxa

Wojtal A Z, Ognjanova-Rumenova N, Buczkó K, Siwek J, Van de Vijver B: Revision of Navicula striolata (Grunow) Lange-Bertalot and N. rumaniensis Hustedt with the description of N. friedelhinziae sp. nov.

Abstract

In the present paper, material collected from the vicinity of Balchik (NE Bulgaria) and housed in the Pantocsek Collection at the Hungarian Natural History Museum (Budapest) has been studied. Ten characteristic diatom species of regional and local importance were revised using scanning electron microscopy in order to clarify their identity. The purpose of the present paper is to elaborate on and photographically document the morphological variability of the examined taxa, and to compare the species composition with previously published data. The presence of Surirella comis Schmidt has been recognized for the first time from Bulgaria, as either fossil or recent form. Species characteristic for the association of the Achnathes baldjikii var. podolica Subzone have been indicated. Its stratigraphic range is within the Sarmatian Stage (Bessarabian Substage).