MTA PE Limnoecology Research Group

Veszprém, Hungary

MTA PE Limnoecology Research Group

Veszprém, Hungary
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Kasprzak P.,Leibniz Institute of Freshwater Ecology and Inland Fisheries | Shatwell T.,Leibniz Institute of Freshwater Ecology and Inland Fisheries | Gessner M.O.,Leibniz Institute of Freshwater Ecology and Inland Fisheries | Gessner M.O.,TU Berlin | And 7 more authors.
Ecosystems | Year: 2017

Climate forecasts project a global increase in extreme weather events, but information on the consequences for ecosystems is scarce. Of particular significance for lakes are severe storms that can influence biogeochemical processes and biological communities by disrupting the vertical thermal structure during periods of stratification. An exceptional storm passing over northern Germany in July 2011 provided an opportunity to assess the consequences and underlying mechanisms of such extreme events on the interplay between the physics and ecological characteristics of a deep, nutrient-poor lake. Wind speeds were among the most extreme on record. A suite of variables measured throughout the event consistently indicates that a cascade of processes pushed the clear-water lake into an exceptionally turbid state. Specifically, thermocline deepening by the storm-entrained cyanobacteria of a deep chlorophyll maximum located at about 8 m depth into the surface mixed layer. Released from light limitation, intense photosynthesis of the cyanobacteria boosted primary production, increased algal biomass, raised the pH and thus induced massive calcite precipitation to a level never observed within three decades of lake monitoring. As a consequence, water transparency dropped from 6.5 to 2.1 m, the minimum on record for 40 years, and the euphotic zone shrank by about 8 m for several weeks. These results show that cyanobacterial blooms not only are promoted by climate warming, but can also be triggered by extreme storms. Clear-water lakes developing a deep chlorophyll maximum appear to be particularly at risk in the future, if such events become more intense or frequent. © 2017 Springer Science+Business Media New York

Tapolczai K.,French National Institute for Agricultural Research | Bouchez A.,French National Institute for Agricultural Research | Stenger-Kovacs C.,University of Pannonia | Stenger-Kovacs C.,MTA PE Limnoecology Research Group | And 3 more authors.
Science of the Total Environment | Year: 2017

Diatom-based ecological quality assessment methods have been implemented and used regularly in the Water Framework Directive. These indices use the species' abundance profiles along a specific environmental gradient, which they aim to assess. However, this approach has several problematic issues including the unstable and fast-changing diatom taxonomy. The use of traits can be a solution if their responses to the environmental pressure are well-defined. Here, we developed taxonomy-based and trait-based diatom assemblage indices to assess the ecological status of riverine sites on a tropical island. The two indices are based on two sub-indices that measure the diatom assemblage response to a nutrient and organic matter/turbidity gradient. Both taxonomy- and trait-based indices correlated significantly with the selected environmental gradients of the test database, which was not used during index development. We showed that traits could be used for quality assessment of the Mayotte rivers and require much less effort than taxonomy-based indices. There were differences between the two types of indices, which are discussed in this paper. As a perspective for further studies, tests of trait-based indices among different eco-regions would be challenging. © 2017 Elsevier B.V.

Selmeczy G.B.,University of Pannonia | Krienitz L.,Leibniz Institute of Freshwater Ecology and Inland Fisheries | Casper P.,Leibniz Institute of Freshwater Ecology and Inland Fisheries | Padisak J.,University of Pannonia | Padisak J.,MTA PE Limnoecology Research Group
Hydrobiologia | Year: 2017

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. © 2017 Springer International Publishing AG

Tapolczai K.,French National Institute for Agricultural Research | Tapolczai K.,University of Pannonia | Anneville O.,French National Institute for Agricultural Research | Padisak J.,University of Pannonia | And 6 more authors.
Hydrobiologia | Year: 2014

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. © 2014, Springer International Publishing Switzerland 2014.

Naselli-Flores L.,University of Palermo | Padisak J.,University of Pannonia | Padisak J.,MTA PE Limnoecology Research Group
Hydrobiologia | Year: 2015

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. © 2015 Springer International Publishing Switzerland

Yang Y.,Uppsala University | Stenger-Kovacs C.,University of Pannonia | Padisak J.,University of Pannonia | Padisak J.,MTA PE Limnoecology Research Group | Pettersson K.,Uppsala University
Hydrobiologia | Year: 2016

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. © 2016 Springer International Publishing Switzerland

Bede-Fazekas A.,Corvinus University of Budapest | Horvath L.,Corvinus University of Budapest | Trajer A.J.,University of Pannonia | Trajer A.J.,MTA PE Limnoecology Research Group | Gregorics T.,Eötvös Loránd University
Applied Artificial Intelligence | Year: 2015

This article is about the development and application of an ESRI ArcGIS tool that implements a multilayer, feed-forward artificial neural network (ANN) to study the climate envelopes of species. The supervised learning is achieved by a backpropagation algorithm. Based on the distribution and the grids of the climate (and edaphic data) of the reference and future periods, the tool predicts the future potential distribution of the studied species. The trained network can be saved and loaded. A modeling result based on the distribution of European larch (Larix decidua Mill.) is presented as a case study. Copyright © 2015 Taylor & Francis Group, LLC.

Tapolczai K.,Thonon les Bains | Bouchez A.,Thonon les Bains | Stenger-Kovacs C.,University of Pannonia | Padisak J.,University of Pannonia | And 2 more authors.
Hydrobiologia | Year: 2016

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. © 2016 Springer International Publishing Switzerland

Trajer A.,University of Pannonia | Trajer A.,MTA PE Limnoecology Research Group | Hammer T.,University of Pannonia
Idojaras | Year: 2016

The potential resurgence of malaria in the temperate areas of Europe due to climate change is an actual topic of epidemiology. Although several ecological forecasting models were built for the prediction of the potential re-emergence of malaria in the recently non-endemic areas of the world, the simulations are mainly based on the recent climatic thresholds of the tropical and subtropical vectors and Plasmodium parasites, mainly of Plasmodium falciparum. We aimed to reanalyze the primarily Plasmodium vivax caused autochthon malaria disease data of the past model period of 1927-1934 in Hungary to gain reliable knowledge about the climatic thresholds and the determinants of the malaria season for a temperate climate in a Central European country. Multivariable and simple linear correlation and regression was performed to analyze the malaria data of 96 months dividing the season a first and a second half parts of the year. Two models were built on the gained correlations using unstandardized and standardized correlation weights. It was found, that both in the first and second halves of the year, the ambient mean temperature was the most important predictor of the relative malaria incidence, while precipitation influenced the first half of the season. Summer sum of precipitation above 200 mm was found as one of the most important determinant of the absolute annual case number of benign tertian malaria. The unstandardized weights-based modeled malaria seasons returned well the observed autochthon malaria seasons. © 2016, Hungarian Meteorological Service. All rights reserved.

Yang Y.,Uppsala University | Pettersson K.,Uppsala University | Padisak J.,University of Pannonia | Padisak J.,MTA PE Limnoecology Research Group
Hydrobiologia | Year: 2015

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. © 2015 Springer International Publishing Switzerland

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