Gábor Borics

Use of Phytoplankton Assemblages for Monitoring Ecological Status of Lakes within the Water Framework Directive: The Assemblage Index

On basis of recent developments in phytoplankton ecology an assemblage index, Q, was developed to assess ecological status of different lake types established by the Water Framework Directive (WFD). Since 5 ≥ Q ≥ 0, the developed index can provide 5-grade qualification required by WFD. Case studies from very different lake types support the usefulness of the developed index. Straights and weaknesses of the Q index for monitoring purposes are discussed. Without arguing for the superiority of the assemblage index in comparison with any other measures of ecological status of lakes, we aim to open a discussion about its possible applications.

Dominant species, functional assemblages and frequency of equilibrium phases in late summer phytoplankton assemblages in Hungarian small shallow lakes

Late summer phytoplankton associations were studied qualitatively and quantitatively in 80 Hungarian lakes altogether (mostly shallow salt lakes, reservoirs, oxbows, gravel pit lakes). Equilibrium phases sensu Sommer et al. (1993) were found only in 17 lakes. Most of them were under some kind (high salt content or very low level of nutrients) of stress factor. It is concluded that environmental stress forces phytoplankton communities towards equilibrium. No relationship between occurrence of equilibria and trophic state was found. Species number of non-equilibrated lakes was almost three times as high as those in equilibrium. Of the 31 recently described (Reynolds et al., 2002) phytoplankton assemblages most of those were recognized that are likely to occur in shallow lakes. Separation of a functional group WS from W2 for Synura dominated lakes is suggested. It seemed also necessary to raise a group (YPh) for lakes dominated by Phacotus. Sorting of Dinophyta species into different already described functional groups is desirable.

Sustaining recreational quality of European lakes: minimizing the health risks from algal blooms through phosphorus control.

1. A safe, clean water supply is critical for sustaining many important ecosystem services provided by freshwaters. The development of cyanobacterial blooms in lakes and reservoirs has a major impact on the provision of these services, particularly limiting their use for recreation and water supply for drinking and spray irrigation. Nutrient enrichment is thought to be the most important pressure responsible for the widespread increase in cyanobacterial blooms in recent decades. Quantifying how nutrients limit cyanobacterial abundance in lakes is, therefore, a key need for setting robust targets for the management of freshwaters. 2. Using a dataset from over 800 European lakes, we highlight the use of quantile regression modelling for understanding the maximum potential capacity of cyanobacteria in relation to total phosphorus (TP) and the use of a range of quantile responses, alongside World Health Organisation (WHO) health alert thresholds for recreational waters, for setting robust phosphorus targets for lake management in relation to water use. 3. The analysis shows that cyanobacteria exhibit a non-linear response to phosphorus with the sharpest increase in cyanobacterial abundance occurring in the TP range from about 20 µg L-1 up to about 100 µg L-1. 4. The likelihood of exceeding the World Health Organisation (WHO) ‘low health alert’ threshold increases from about 5% exceedance at 16 µg L-1 to 40% exceedance at 54 µg L-1. About 50% of the studied lakes remain below this WHO health alert threshold, irrespective of high summer TP concentrations, highlighting the importance of other factors affecting cyanobacteria population growth and loss processes, such as high flushing rate. 5. Synthesis and applications. Developing a more quantitative understanding of the effect of nutrients on cyanobacterial abundance in freshwater lakes provides important knowledge for restoring and sustaining a safe, clean water supply for multiple uses. Our models can be used to set nutrient targets to sustain recreational services and provide different levels of precaution that can be chosen dependent on the importance of the service provision.

Strength and uncertainty of phytoplankton metrics for assessing eutrophication impacts in lakes

Phytoplankton constitutes a diverse array of short-lived organisms which derive their nutrients from the water column of lakes. These features make this community the most direct and earliest indicator of the impacts of changing nutrient conditions on lake ecosystems. It also makes them particularly suitable for measuring the success of restoration measures following reductions in nutrient loads. This paper integrates a large volume of work on a number of measures, or metrics, developed for using phytoplankton to assess the ecological status of European lakes, as required for the Water Framework Directive. It assesses the indicator strength of these metrics, specifically in relation to representing the impacts of eutrophication. It also examines how these measures vary naturally at different locations within a lake, as well as between lakes, and how much variability is associated with different replicate samples, different months within a year and between years. On the basis of this analysis, three of the strongest metrics (chlorophyll-a, phytoplankton trophic index (PTI), and cyanobacterial biovolume) are recommended for use as robust measures for assessing the ecological quality of lakes in relation to nutrient-enrichment pressures and a minimum recommended sampling frequency is provided for these three metrics.

Phytoplankton associations in a small hypertrophic fishpond in East Hungary during a change from bottom-up to top-down control

Phytoplankton species composition and abundance of a shallow hypertrophic fishpond (Mézeshegyi-tó, East Hungary) was studied for the period 1992–1995. The pond showed a pronounced algal periodicity. High-diversity phytoplankton assemblages occurred in spring and autumn. During the winter period, low diversity values were related either to stable community states, when K-strategist species dominated the plankton, or to a large bloom of r-strategist species. In summer, the stable environment led to low-diversity, high-biomass phytoplankton assemblages, dominated by Cylindrospermopsis raciborskii. At this time, the growth conditions for Cylindrospermopsiswere akin to those prevailing in a continuous fermentor. The overwhelming dominance of this species lasted for more than four months, during which time, the phytoplankton resembled that of one in the tropics. In August, 1993, an unsuccessful chemical treatment for reducing the algal bloom succeeded in killing the ponds entire population of fish. The large fish-stock comprised the planktivorous silver carp. Although the summer of 1994 was one of the warmest summers of this century, the expected Cylindrospermopsis bloom failed to develop probably because of a higher grazing pressure by large zooplankton. In spite of the fact that the temporal and spatial pattern of the phytoplankton is influenced principally by bottom-up effects, changes in cascading trophic interactions may also considerably influence the species composition and biomass.

Algal assemblage types of bog-lakes in Hungary and their relation to water chemistry, hydrological conditions and habitat diversity

Algal flora of 12 bog lakes was investigated during the period of March 1995 to August 1999 in Hungary. Of the 129 samples, 624 taxa of algae were identified. Species richness of individual samples ranged between 8 and 107 except the extraordinarily species rich Baláta-tó where 533 algal taxa were observed. Ordination of the samples resulted in five groups: (1) assemblages dominated by chlorococcalean algae and planktonic Cyanoprokaryota; (2) assemblages dominated by flagellates (Dinophyta, Cryptophyta, Euglenophyta, Chrysophyceae, Raphidophyceae); (3) chlorococcalean algae and cyanoprokaryotic assemblages with desmids, cryptophytes, dinoflagellates or euglenophytes as subdominants; (4) assemblages dominated by diatoms and (5) a group of samples where other taxa belonging to Xanthophyta and filamentous green algae dominated. The bogs were typically rich in inorganic N and P, moreover, their water chemical characteristics (including pH and conductivity) were rather uniform. Therefore, other factors than chemical properties were responsible for different flora. The above groups were characteristic to certain types of habitats. In the first group, plankton samples from relatively large pools with considerable open water can be found. The second group included samples taken from small bog pools. The third group contained the periphyton samples from macrophytes, living in bogs with constantly reliable water supply. Samples of group four and five comprised small bogs that occasionally dry up. Periphyton of lakes with Sphagnum belonged exclusively to the fifth group. This study has shown that small bog-pools are often inhabited by different species of flagellates and desmids are not as important as it has been widely believed. Hydrological properties and habitat diversity are the major factors influencing species richness of Hungarian bog-lakes.

Phytoplankton functional and morpho-functional approach in large floodplain rivers

Influence of hydrological characteristics and nutrient concentrations on phytoplankton was investigated in four large rivers (Mura, Drava, Danube and Sava) in the Pannonian ecoregion in Croatia to understand how phytoplankton of rivers can be explained by the “different functional group approach”. To gain a clearer understanding of the factors that affect river phytoplankton, the present study examined phytoplankton biomass and composition in relationship with physical and chemical parameters assessed in detail by preparing self-organising maps using functional groups and morpho-functional groups. Total nitrogen along with water residence time showed to be the best predictor to determine phytoplankton biomass and chlorophyll a. Phytoplankton diversity increased with higher water discharge, but it had the consequence of diluting algae and decreasing biomass. Bacillariophyceae and Chlorophyceae species dominated the phytoplankton assemblages in all rivers. Diatoms predominated in rivers with shorter residence time. Dominant diatom codons of functional groups were C, D and TB while morpho-functional groups were represented by only diatom group VI. As residence time increased, the proportion of chlorococcalean green algae, represented by functional group codon T and morpho-functional group IV grew in summer. Since potamoplankton is dominated by diatoms, functional groups with its fine partition of diatom codons proved to be excellent descriptor of the potamoplankton. Application of morpho-functional groups originally developed from the lake data, showed to be limiting because of the predominating presence of only one diatom group.

Characteristics of the pelagic phytoplankton in shallow oxbows

Numerous oxbows of different sizes, depths and ages accompany alluvial rivers in the Carpathian basin. These water bodies provide various habitats for macroscopic and microscopic assemblages. Phytoplankton of 13 oxbows in the Tisza valley was studied between 2005 and 2008. In this article, we focussed on the following questions (i) do the oxbows have unique microflora? (ii) does the macrophyte coverage have a large effect on the composition and biomass of the algal assemblages? and (iii) does the higher plants dominated state result in clear-water conditions in the oxbows? The studied oxbows were in different stages of the ageing process. We classified the sampled oxbows according to their macrophyte vegetation into five types. A total of 646 species of algae were recorded in the oxbows over the study period. The microflora was dominated by cyanophytes, chlorococcalean green algae, euglenophytes and diatom species. Phytoplankton species were allocated into 32 coda. For the determination of typical algal assemblages, we used Kohonen’s Self Organizing Map (SOM) statistical analysis combined with K-means clustering, which has resulted five different types of phytoplankton associations. These types were dominated by coda Y, LO, W1, WS and J. Chlorophyll a data of the sparsely and densely vegetated oxbows did not differ, since a wide range of values characterised both types of the lakes. In this study, the composition of the microflora is similar to that of other eutrophic lakes, but some rarely occurring taxa such as Peridinium gatunense Nygaard and Peridiniopsis elpatiewskyi (Ostenf.) Bourelly might play a key role in the phytoplankton succession of the oxbows. The effect of the macrophyte coverage was decisive in the composition of the algal assemblages, and our investigations indicated that, in the case of the oxbows, the macrophyte-dominated state does not necessarily result in a clear-water state.

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.

Littoral macrophyte-periphyton complexes in two Hungarian shallow waters

Periphyton developing on the surfaces of emergent and submerged aquatic plants has a significant influence on water quality. The periphyton types that form on various plant species can be characterized by their mass values, the proportion of the present organic and inorganic fractions, as well as their chlorophyll-a contents. Studies on periphyton complexes constituting integrated biomonitoring systems are useful to gain essential long-term information about the performance of shallow water bodies. The filtering and settling effect of Phragmites and other aquatic plants, as well as their periphyton was examined and clearly observable in the water areas and non-flooded aquatic habitats belonging to the second phase of Kis-Balaton Protection System, as it was indicated by the mass values and ash contents. The periphyton forming on the aquatic vegetation that annually develops in Kisköre Reservoir and yields a considerable biomass has a critical part in influencing water quality. The only difference (p<0.05) was found in the ash content of the periphyton, being lower in Kis-Balaton (48.64 ± 2.29 S.E., %) and higher in Kisköre Reservoir (57.42 ± 2.54 S.E., %). This paper presents the dry mass of the periphyton, as well as its ash and chlorophyll-a content, and the results obtained on the composition of the alga species of the periphyton.