Társadalmi konfliktusokat generáló ökológiai történések a Balaton életében az utóbbi néhány évtizedben – A víz zöld elszíneződése, az eutrofizáció

Social Conflict Generating Ecological Developments in the Life of Lake Balaton in Recent Decades – Eutrophication, the green discolouration of the water As a result of increased nutrient loads affecting Lake Balaton phytoplankton biomass showed a considerable rise from the 1970s onwards, particularly in summer, indicating eutrophication, a process eventually leading to unfavourable ecological conditions. Summer blooms were increasingly dominated by filamentous N2-fixing cyanobacteria, particularly in the western basin showing a shift from eutrophic to hypertrophic state. Increased phosphorus loading was found to be the major cause of eutrophication in the lake, thus, in order to eliminate the sources of excessive nutrient input and its harmful consequences the 1980s saw the elaboration of reasoned restoration efforts including the adoption of phosphorus removal in wastewater treatment, sewage water diversion and the establishment of the Kis-Balaton reservoir. Due to these technical solutions eutrophication has been reversed, the trophic state of the lake has been showing a decreasing trend since 1995.Social Conflict Generating Ecological Developments in the Life of Lake Balaton in Recent Decades – Eutrophication, the green discolouration of the water As a result of increased nutrient loads affecting Lake Balaton phytoplankton biomass showed a considerable rise from the 1970s onwards, particularly in summer, indicating eutrophication, a process eventually leading to unfavourable ecological conditions. Summer blooms were increasingly dominated by filamentous N2-fixing cyanobacteria, particularly in the western basin showing a shift from eutrophic to hypertrophic state. Increased phosphorus loading was found to be the major cause of eutrophication in the lake, thus, in order to eliminate the sources of excessive nutrient input and its harmful consequences the 1980s saw the elaboration of reasoned restoration efforts including the adoption of phosphorus removal in wastewater treatment, sewage water diversion and the establishment of the Kis-Balaton reservoir. Due to these technical solutions eutrophication has been reversed, the trophic state of the lake has been showing a decreasing trend since 1995

Diversity patterns of trait-based phytoplankton functional groups in two basins of a large, shallow lake (Lake Balaton, Hungary) with different trophic state

The application of functional approaches in understanding phytoplankton community-level responses to changes in the environment has become increasingly widespread in recent years. Eutrophication is known to cause profound modifications in ecosystem processes, however, the underlying relationships between environmental drivers and phytoplankton diversity and functioning are complex and largely unknown. Therefore, in the present study we investigated and compared the temporal diversity patterns of phytoplankton functional groups in the mesotrophic eastern and eutrophic western basin of the shallow Lake Balaton situated in Hungary. Diversity data were derived from taxonomic composition and biomass data corresponding to the years 2005-2006 and 2008-2009. With the use of cluster analysis phytoplankton species were classified into eight distinct groups representing different combinations of functionally relevant traits including greatest axial linear dimension, surface to volume ratio, photosynthetic pigment composition, N2-fixation, phagotrophic potential, growth form/complexity (unicell, filamentous, colony- or coenobiumforming) and motility. Our results have revealed that there is a significant inverse relationship between the functional group diversity used in our study and trophic state (total phytoplankton biomass) as opposed to species diversity, where no correlation was observed. In addition, group evenness showed an even stronger negative correlation with trophic state, while species evenness yielded only a weak relationship. The observed variability in functional group diversity suggests that such an approach could provide an efficient means of revealing structural changes in phytoplankton communities, establishing new hypotheses and highlighting fundamental points in ecosystem functioning

Phytoplankton functional composition shows higher seasonal variability in a large shallow lake after a eutrophic past

Abstract Eutrophication is a well‐known problem of global proportions with some easily recognizable and potentially harmful effects on aquatic habitats, but our knowledge on the underlying associated changes in ecosystem functioning is rather limited. Relevant studies suggest that seasonal variability in the functional composition of phytoplankton shows an increase as eutrophication progresses. The aim of the present study was to test this hypothesis through the assessment of long‐term changes in the functional diversity and composition of phytoplankton in a large shallow lake situated in Central Europe with a history of dramatic changes in trophic state. Contrary to our expectations, results have shown that the maximum range of compositional variability had a significant negative correlation with the summer biomass maxima. On the other hand, average seasonal variability measured as annual beta diversity exhibited an increasing trend throughout the years from the period of early eutrophication to the recent period of reoligotrophication, seemingly following a decline in functional richness and a long‐term rise in annual mean water temperature. The enhanced variability in phytoplankton succession implies that all the ecosystem processes connected to the phytoplankton follow more complex seasonal dynamics. Besides changing community structure, trophic state also seems to be an important factor in setting the limits to compositional changes during the annual cycle, whereas long‐term warming is likely to enhance instability in the phytoplankton. The trajectories of these two factors and the changes in seasonal succession indicate a lake in transition, urging more in‐depth research efforts to understand the impact of climate change on this specific ecosystem, and raise the question of whether the observed changes can also occur in other similar aquatic systems

The effects of interspecific interactions between bloom forming cyanobacteria and Scenedesmus quadricauda (chlorophyta) on their photophysiology

Eutrophication and enhanced external nutrient loading of lakes and seas are most clearly reflected by increased cyanobacterial blooms, which are often toxic. Freshwater cyanobacteria produce a number of bioactive secondary metabolites, some of which have allelopathic properties, significantly influencing the biological processes of other algae, thereby affecting species composition and succession of the phytoplankton. The goal of this work was to investigate the influence of bloom-forming cyanobacterial exudates on the photophysiology of the green alga Scenedesmus quadricauda by chlorophyll fluorescence analysis. We were able to prove the effect of algal cell-free filtrates on the performance of S. quadricauda and demonstrate for the first time that the freshwater picocyanobacterium Cyanobium gracile has strong negative impact on the coexisting green alga. Neither the cyanotoxin (MYC, CYN and ATX) producing, nor the non-toxic strains showed any systematic effect on the production of S. quadricauda. Various strains of the cyanobacterium Cylindrospermopsis raciborskii inhibited the performance of the green alga independently of their origin. Our results urge further studies for a better understanding of the factors affecting the release of allelopathic compounds and the mechanisms of their effects on target organisms

Remote Sensing of Water Quality Parameters over Lake Balaton by Using Sentinel-3 OLCI

Source at https://doi.org/10.3390/w10101428.The Ocean and Land Color Instrument (OLCI) onboard Sentinel 3A satellite was launched in February 2016. Level 2 (L2) products have been available for the public since July 2017. OLCI provides the possibility to monitor aquatic environments on 300 m spatial resolution on 9 spectral bands, which allows to retrieve detailed information about the water quality of various type of waters. It has only been a short time since L2 data became accessible, therefore validation of these products from different aquatic environments are required. In this work we study the possibility to use S3 OLCI L2 products to monitor an optically highly complex shallow lake. We test S3 OLCI-derived Chlorophyll-a (Chl-a), Colored Dissolved Organic Matter (CDOM) and Total Suspended Matter (TSM) for complex waters against in situ measurements over Lake Balaton in 2017. In addition, we tested the machine learning Gaussian process regression model, trained locally as a potential candidate to retrieve water quality parameters. We applied the automatic model selection algorithm to select the combination and number of spectral bands for the given water quality parameter to train the Gaussian Process Regression model. Lake Balaton represents different types of aquatic environments (eutrophic, mesotrophic and oligotrophic), hence being able to establish a model to monitor water quality by using S3 OLCI products might allow the generalization of the methodology

Unique picoeukaryotic algal community under multiple environmental stress conditions in a shallow, alkaline pan

Winter phytoplankton communities in the shallow alkaline pans of Hungary are frequently dominated by picoeukaryotes, sometimes in particularly high abundance. In winter 2012, the ice-covered alkaline Zab-sze´k pan was found to be extraordinarily rich in picoeukaryotic green algae (42–82 9 106 cells ml-1) despite the simultaneous presence of multiple stressors (low temperature and light intensity with high pH and salinity). The maximum photosynthetic rate of the picoeukaryote community was 1.4 lg C lg chlorophyll a-1 h-1 at 125 lmol m-2 s-1. The assimilation rates compared with the available light intensity measured on the field show that the community was considerably light-limited. Estimated areal primary production was 180 mg C m-2 d-1. On the basis of the 18S rRNA gene analysis (cloning and DGGE), the community was phylogenetically heterogeneous with several previously undescribed chlorophyte lineages, which indicates the ability of picoeukaryotic communities to maintain high genetic diversity under extreme conditions

Koncepcióváltás a belvízgazdálkodásban: talajtani és vízminőségi kérdések = Conceptual Change in Excess Water Management: Soil and Water Quality Issues

Munkánk során igyekeztünk a belvízminőséggel, annak időbeli változásaival kapcsolatos kérdéseket megválaszolni

Unusual behaviour of phototrophic picoplankton in turbid waters

Autotrophic picoplankton (APP) abundance and contribution to phytoplankton biomass was studied in Hungarian shallow lakes to test the effect of inorganic turbidity determining the size distribution of the phytoplankton. The studied lakes displayed wide turbidity (TSS: 4–2250 mg l-1) and phytoplankton biomass (chlorophyll a: 1–460 μg l-1) range, as well as APP abundance (0 and 100 million cells ml-1) and contribution (0–100%) to total phytoplankton biomass. Inorganic turbidity had a significant effect on the abundance and contribution of APP, resulting in higher values compared to other freshwater lakes with the same phytoplankton biomass. Our analysis has provided empirical evidence for a switching point (50 mg l-1 inorganic turbidity), above which turbidity is the key factor causing APP predominance regardless of phytoplankton biomass in shallow turbid lakes. Our results have shown that turbid shallow lakes are unique waters, where the formerly and widely accepted model (decreasing APP contribution with increasing phytoplankton biomass) is not applicable. We hypothesize that this unusual behaviour of APP in turbid waters is a result of either diminished underwater light intensity or a reduced grazing pressure due to high inorganic turbidity

Picophytoplankton predominance in hypersaline lakes (Transylvanian Basin, Romania)

The occurrence and importance of photoautotrophic picoplankton (PPP, cells with a diameter <2μm) was studied a long a trophic and salinity gradient in hypersaline lakes of the Transylvanian Basin (Romania. The studied lakes were found to be rich in PPP, with abundances (maximum:7.6 x 106 cells mL - ) higher than in freshwater and marine environments of similar trophic conditions. The contribution of PPP to the total phytoplankton bio volume did not decrease with in creasing trophic state as it was generally found in other aquatic environments. Regardless of the trophic conditions, the contribution of PPP could reach 90-100% in these hypersaline lakes. We hypothesized that the PPP predominance might be the result of the low grazing pressure, since heterotrophic nanoflagellates (the main grazers of PPP) were absent in the studied samples. There were significant differences in community composition among the lakes a long the salinity gradient. CyPPP predominated in less saline waters (mainly below 5%), while EuPPP were present along the entire salinity range (up to 18.7%), dominating the phytoplankton between 3 and 13% salin ity . Above 13% salinity, the phytoplankton was composed mainly of Dunaliella species

Environmental changes associated with drying climate are expected to affect functional groups of pro- and microeukaryotes differently in temporary saline waters

Temporary ponds are among the most sensitive aquatic habitats to climate change. Their microbial communities have crucial roles in food webs and biogeochemical cycling, yet how their communities are assembled along environmental gradients is still understudied. This study aimed to reveal the environmental drivers of diversity (OTU-based richness, evenness, and phylogenetic diversity) and community composition from a network of saline temporary ponds, soda pans, in two consecutive spring seasons characterized by contrasting weather conditions. We used DNA-based molecular methods to investigate microbial community composition. We tested the effect of environmental variables on the diversity of prokaryotic (Bacteria, Cyanobacteria) and microeukaryotic functional groups (ciliates, heterotrophic flagellates and nanoflagellates, fungi, phytoplankton) within and across the years. Conductivity and the concentration of total suspended solids and phosphorus were the most important environmental variables affecting diversity patterns in all functional groups. Environmental conditions were harsher and they also had a stronger impact on community composition in the dry spring. Our results imply that these conditions, which are becoming more frequent with climate change, have a negative effect on microbial diversity in temporary saline ponds. This eventually might translate into community-level shifts across trophic groups with changing local conditions with implications for ecosystem functioning