One of the most important physical characteristics driving lifecycle events in lakes is stratific... more One of the most important physical characteristics driving lifecycle events in lakes is stratification. Already subtle variations in the timing of stratification onset and break-up (phenology) are known to have major ecological effects, mainly by determining the availability of light, nutrients, carbon and oxygen to organisms. Despite its ecological importance, historic and future global changes in stratification phenology are unknown. Here, we used a lake-climate model ensemble and long-term observational data, to investigate changes in lake stratification phenology across the Northern Hemisphere from 1901 to 2099. Under the high-greenhouse-gas-emission scenario, stratification will begin 22.0 ± 7.0 days earlier and end 11.3 ± 4.7 days later by the end of this century. It is very likely that this 33.3 ± 11.7 day prolongation in stratification will accelerate lake deoxygenation with subsequent effects on nutrient mineralization and phosphorus release from lake sediments. Further mis...
The review intends to give an overview on developments, success, results of photosynthetic resear... more The review intends to give an overview on developments, success, results of photosynthetic research and on primary productivity of algae both freshwater and marine with emphasis on more recent discoveries. Methods and techniques are briefly outlined focusing on latest improvements. Light harvesting and carbon acquisition are evaluated as a basis of regional and global primary productivity and algal growth. Thereafter, long-time series, remote sensing and river production are exemplified and linked to the potential effects of climate change. Lastly, the synthesis seeks to put the life achievements of Colin S. Reynolds into context of the subject review.
Background. Poyang Lake is an exceptional system exhibiting a water level change of up to 14 m ev... more Background. Poyang Lake is an exceptional system exhibiting a water level change of up to 14 m every year. In the years 2013 and 2014 water level changes were 8.03 m and 11.22m respectively. The biomass of Anabaena and heterocyst frequency increased in the summers of recent years. Methods. A weekly or bi-weekly monitoring period from June to November 2013 and 2014 was set up to explain the reason for this phenomenon. Results. Anabaena was observed throughout the year. The average relative biomass of Anabaena in the study period was over 40%, being most abundant in summer. The average heterocyst frequency was 0.226% in 2013 and 0.760% in 2014. The SPSS analysis indicated a positive correlation of Anabaena biomass with water temperature and water level and negative one with TN, which is the reason for the increase of heterocyst frequency from 2013 to 2014. It also indicated that heterocyst frequency of Anabaena was positively correlated with water temperature, water level and PO4-P, a...
Aquatic ecosystems are of critical ecological, social and economic importance. Worldwide increase... more Aquatic ecosystems are of critical ecological, social and economic importance. Worldwide increase in their use and anthropogenic pressures alter their health which is essential for the maintenance of water quality, biodiversity, and fishing activities. The European Parliament sets out a framework for managing and protecting water for each main catchment basin at a European level. The aim is to propose objectives to conserve or restore the state of water-bodies into a status that would be considered "good" in development and ecological terms. A key issue in the implementation of the Water Framework Directive is the classification of water-bodies into "quality status" using biological indices. Comparison and classification of water bodies throughout Europe require the improvement and development of new methodologies based upon scientific knowledge. New methods and indices have been proposed for categorizing water bodies into quality status. In this study we took advantage of the long-term data set of phytoplankton abundance and composition sampled in Lake Geneva (France-Switzerland) to test an index formally developed for Austrian lakes. Lake Geneva has suffered from eutrophication in the 80's. Comparisons between the tested and classical indices show that recovery from eutrophication is a long process that could be altered by large scale pressures such as climate change.
This review summarizes winter conditions from six polymictic European shallow lakes. The lakes ra... more This review summarizes winter conditions from six polymictic European shallow lakes. The lakes range from oligotrophic to hyper-eutrophic. Four of the lakes freeze regularly while ice cover is absent or rare in the two others. Ice duration and timing of ice-out are significantly influenced by climate signals in three of the lakes. Winter water temperature remains higher in nonice-covered lakes. No long-term trend in temperature is detectable except for one lake where winter water temperature began to increase in 1986. Secchi depth in winter is equal or greater than summer values in all six lakes indicating relatively better light conditions in winter. Total phosphorus concentration in winter ranges from 10 to 130 µg L-1 , which is equal or lower than summer values and is unrelated to chlorophyll a in five of the sites. Phytoplankton species composition during winter differs largely at the six sites. The winter assemblages largely depend on the trophic level and the conditions during the previous season. Winter chlorophyll a and phytoplankton biomass are usually lower than summer values because of reduced photosynthetic rates. Bacterial production often exceeds primary production. Epipelic algal assemblages tend to proliferate during winter in both ice-covered and non-ice-covered lakes. Primary production is low during winter because of insufficient light. Zooplankton abundances and biomass critically depend on conditions during the previous season and the winter situation and are quite variable from year to year, but their values correlate with the trophic status of the lakes. As a result, winter conditions are important to understand seasonal and annual changes in shallow lakes.
Long-term phytoplankton assemblages in a large shallow Chinese lake, Lake Taihu, were presented u... more Long-term phytoplankton assemblages in a large shallow Chinese lake, Lake Taihu, were presented using the monthly monitoring data from October 1991 to December 1999. Earlier research results (1960, 1981 and 1988) were applied to discuss the different trophic stages of the lake. The species composition in the lake was more closely related to eutrophication level than to lake-size, shallowness, or turbidity. Each summer, a single peak of phytoplankton biovolume appeared in Meiliang Bay. The results of principal components analysis showed a distinct temporal shift in species composition between summer and winter. A clear spatial difference in phytoplankton occurred between Meiliang Bay and the lake centre. Wind speed and direction affected the horizontal distribution of phytoplankton, especially Microcystis, in the lake. Temperature, underwater light climate, nutrients and grazing by zooplankton and by fish were discussed to explain the overwhelming dominance of Microcystis. Four nutri...
Eutrophication: Causes, Consequences and Control, 2013
Ecosystem services are the benefits provided to people by ecosystems and biodiversity. Fresh wate... more Ecosystem services are the benefits provided to people by ecosystems and biodiversity. Fresh water is a ' provisioning' service referring to the human use offresh water for several purposes. The hydrological cycle also sustains inland water ecosystems, including rivers, lakes and wetlands. These ecosystems provide regulating, supporting and cultural services that contribute directly and indirectly to human well-being through recreation, seenie values and fisheries. To maintain ecosystem health or ecosystem integrity, extemal or intemal perturbations must be kept below the carrying capacity. Anthropogenie disturbances offreshwater resources as a consequence oftourism are diverse. In many regions of the world, lakes and ponds in particular are important freshwater habitats providing significant attraction for the public. Impacts to lakes from tourist activities occur directly to the lake water and shoreline, or can affect the water body indirectly through various actions in the catchment. The response of a specific freshwater ecosystem depends on the type of interference as well as the type and size of the lake. Shallow lakes are affected and hence behave differently from deep lakes. Large lakes react in a different way than smalllakes. Impacts are also modified and mediated by the characteristics of the catchment, such as morphology, size, land-use and population structure. Impacts to tourist lakes are classified as direct and indirect effects and are analysed and exemplified.
In this chapter, the quantitative changes of the components of the hydrosphere are analyzed for t... more In this chapter, the quantitative changes of the components of the hydrosphere are analyzed for the period from 1950 to 2010 and then for the period from 2 000 until the end of this century. For the first period, the observed changes are descri- bed by analyzing the time series of snow depth, glacier volu- mes, surface runoff, water temperatures and groundwater tab- les. For the future period from 2010 to 2100, regional climate models are applied in order to provide the input to various hydrological models. In particular, results were selected from the CLM-ECHAM5-A1B and REMO-UBA models, with SRES emission scenarios A2, A1B and B1, as well as the A1B simulation from the ARPEGE-ALADIN and Reg-CM3 from the ENSEMBLES project. Additionally, two scenarios from the 5th IPCC-Assessment Report (RCP2.6 und RCP8.5) were analysed with respect to the impacts on glaciers. The data show that in Austria, since 1980 the snow line has shifted upwards, predominantly in the summer season. This is cons...
Alte Donau nowadays is an eutrophic urban lake within the city of Vienna. Increasing nutrient con... more Alte Donau nowadays is an eutrophic urban lake within the city of Vienna. Increasing nutrient concentrations and massive blooms of cyanobacteria mainly caused by Limnothrix redekei Van Goor and Cylindrospermopsis raciborskii (Wołsz.) Seenayya et Subba Raju were recently registered. As a consequence Secchi depth was significantly reduced especially during the summer season (minimum: 0.25 m). An investigation including water chemistry, phytoplankton, macrophytes, and sediment was initiated in 1993 and extended to metazooplankton, ciliates and bacteria in 1994. The first half of the year 1994 was characterised by relatively clear water and a high diversity of the phytoplankton composition due to flushing of the lake with water of better quality by the end of 1993. Ciliates and metazooplankton held about 10% of the total biomass of all the investigated trophic levels. The vanishing of the remaining macrophytes enlarged the nutrient supply during summer 1994 and favoured the development of cyanobacteria. The high water temperatures which excluded certain zooplankton species, and the inedibility of the filaments further increased the dominance of cyanobacteria. In November, when the algal bloom finally ceased, the highest bacterial numbers of the investigation period occurred. Thereafter, other algal groups, bacteria and metazooplankton gained more importance. Interactions are possible because of close overlap in space and time due to the turbulent mixed conditions of the water body and the change from the macrophyte dominated to the algal dominated stable state. Planned restoration measures must aim to re-establish the previous macrophyte dominated clear-water stage.
One of the key actions identified by the Water Framework Directive (WFD; 2000/60/EC) is to develo... more One of the key actions identified by the Water Framework Directive (WFD; 2000/60/EC) is to develop ecological assessment tools and carry out a European intercalibration (IC) exercise. The aim of the Intercalibration is to ensure that the values assigned by each Member State to the good ecological class boundaries are consistent with the Directive’s generic description of these boundaries and comparable to the boundaries proposed by other MS. In total, 83 lake assessment methods were submitted for the 2nd phase of the WFD intercalibration (2008-2012) and 62 intercalibrated and included in the EC Decision on Intercalibration (EC 2013). The intercalibration was carried out in the 13 Lake Geographical Intercalibration Groups according to the ecoregion and biological quality element. In this report we describe how the intercalibration exercise has been carried out in the Alpine Lake Phytoplankton Intercalibration group
The Ecological Bases for Lake and Reservoir Management, 1999
Recent changes which have been observed at Alte Donau, a shallow urban lake within the city of Vi... more Recent changes which have been observed at Alte Donau, a shallow urban lake within the city of Vienna, have been interpreted as a shift to a new stable state. The former macrophyte-dominated state changed to a turbid state dominated by high biomass of filamentous cyanobacteria, associated with a significant reduction in Secchidepth. Phytoplankton was dominated by the filamentous cyanobacterial species Cylindrospermopsis raciborskii (Wolosz.), Seenayya et Subba Raju and Limnothrix redekei (Van Goor) Meffert. Integrated restoration plans included internal and external measures. Improvements in the catchment aim to minimize the input of nutrients from contaminated groundwater and from storm water and to reduce large numbers of water fowl. Internal restoration measures included water exchange, chemical flocculation and nitrate oxidation of the sediments. Additionally, macrophyte re-colonisation was enhanced through planting. A pelagic predator (Aspius aspius L.) was stocked to reduce bleak (Alburnus alburnus L.), the dominant cyprinid planktivore. Results from the period after water exchange and chemical treatment, showed significant reduction of nutrient and chlorophyll a concentrations. A shift in the phytoplankton species from cyanobacteria towards diatoms and greens was observed. Secchi depth greatly increased. Macrophyte growth became apparent both through re-colonisation, as well as from the planting.
Climate change impacts include such an overwhelming number of facets that the extent of reference... more Climate change impacts include such an overwhelming number of facets that the extent of references is impossible to cover. The selection presented in this review on global warming is presumably subjective, although the author has tried to assemble relevant and/or most recent information. The references specified should be regarded as examples that direct the reader to more information on a specific subject.
In Europe, the effects of global warming are expected to be particularly acute in areas exposed t... more In Europe, the effects of global warming are expected to be particularly acute in areas exposed to a more extreme continental climate. The climate change scenarios summarized in Chapter 2, this volume, suggest that the average summer temperatures in some areas of Central Europe could increase by as much as 6 • C by 2071-2100. The associated projections for the rainfall give even more cause for concern with the reductions in some areas approaching 50% in summer. In this chapter we analyse impacts of changing weather conditions on lakes in Central Europe. Long-term data sets from a number of lakes are used to link measured variables to climate signals. Particular attention is paid to the lakes in the perialpine region which are known to be very sensitive to short-term changes in the weather (Psenner, 2003; Thompson et al., 2005). Here, the topography and the steep orography enhance the water cycle, and result in flooding, debris flows, avalanches, vertical plant migration etc. The Alps also form a barrier to the mass movement of air and are responsible for the sharp climatic divide between Atlantic, Continental and Mediterranean influences. Central Europe is a variously and vaguely defined region. Rather than a physical entity, it is more a reflection of a shared history. The results summarized here are based on the analysis of long-term climatological and limnological data from the countries shown in Fig. 20.1. These include Germany (DE), Poland (PL), the Czech Republic (CZ), Slovakia (SK), Switzerland (CH), Lichtenstein (LI), Austria (AT) and Hungary (HU). The Central European countries are geographically diverse with landforms ranging from the North-German Lowlands, through the Alps to the Hungarian plain. The pannonian plain in the eastern part is also a major climatic 'crossing point' and is affected by the Eastern-European continental, the Western-European oceanic and the Mediterranean influence.
The Impact of Climate Change on European Lakes, 2009
Fig.17.2 An overview of the factors affecting the relationship between climatic forcing and the p... more Fig.17.2 An overview of the factors affecting the relationship between climatic forcing and the physical lake response to this forcing Climate: Spatially and temporally coherent Degree cif spatial coherence deriendson scale (regional, synoptic, hemlspherlc,global) Weather; Local manifestation of climate Air temperature Cloud cover Relative humidity Wind speed
Twenty to fifty years of annual mean deepwater (hypolimnetic) temperature data from twelve deep l... more Twenty to fifty years of annual mean deepwater (hypolimnetic) temperature data from twelve deep lakes spaced across Europe (2u959W to 14u09E, 46u279 to 59u009N) show a high degree of coherence among lakes, particularly within geographic regions. Hypolimnetic temperatures vary between years but increased consistently in all lakes by about 0.1-0.2uC per decade. The observed increase was related to the weather generated by largescale climatic processes over the Atlantic. To be effective, the climatic signal from the North Atlantic Oscillation (NAO) must affect deep lakes in spring before the onset of thermal stratification. The most consistent predictor of hypolimnetic temperature is the mean NAO index for January-May (NAO J-M), which explains 22-63% of the interannual variation in deepwater temperature in 10 of the 12 lakes. The two exceptions are remote, less windexposed alpine valley lakes. In four of the deepest lakes, the climate signal fades with depth. The projected hypolimnetic temperature increase of approximately 1uC in 100 yr, obtained using a conservative approach, seems small. Effects on mixing conditions, thermal stability, or the replenishment of oxygen to deep waters result in accumulation of nutrients, which in turn will affect the trophic status and the food web.
One of the most important physical characteristics driving lifecycle events in lakes is stratific... more One of the most important physical characteristics driving lifecycle events in lakes is stratification. Already subtle variations in the timing of stratification onset and break-up (phenology) are known to have major ecological effects, mainly by determining the availability of light, nutrients, carbon and oxygen to organisms. Despite its ecological importance, historic and future global changes in stratification phenology are unknown. Here, we used a lake-climate model ensemble and long-term observational data, to investigate changes in lake stratification phenology across the Northern Hemisphere from 1901 to 2099. Under the high-greenhouse-gas-emission scenario, stratification will begin 22.0 ± 7.0 days earlier and end 11.3 ± 4.7 days later by the end of this century. It is very likely that this 33.3 ± 11.7 day prolongation in stratification will accelerate lake deoxygenation with subsequent effects on nutrient mineralization and phosphorus release from lake sediments. Further mis...
The review intends to give an overview on developments, success, results of photosynthetic resear... more The review intends to give an overview on developments, success, results of photosynthetic research and on primary productivity of algae both freshwater and marine with emphasis on more recent discoveries. Methods and techniques are briefly outlined focusing on latest improvements. Light harvesting and carbon acquisition are evaluated as a basis of regional and global primary productivity and algal growth. Thereafter, long-time series, remote sensing and river production are exemplified and linked to the potential effects of climate change. Lastly, the synthesis seeks to put the life achievements of Colin S. Reynolds into context of the subject review.
One of the most important physical characteristics driving lifecycle events in lakes is stratific... more One of the most important physical characteristics driving lifecycle events in lakes is stratification. Already subtle variations in the timing of stratification onset and break-up (phenology) are known to have major ecological effects, mainly by determining the availability of light, nutrients, carbon and oxygen to organisms. Despite its ecological importance, historic and future global changes in stratification phenology are unknown. Here, we used a lake-climate model ensemble and long-term observational data, to investigate changes in lake stratification phenology across the Northern Hemisphere from 1901 to 2099. Under the high-greenhouse-gas-emission scenario, stratification will begin 22.0 ± 7.0 days earlier and end 11.3 ± 4.7 days later by the end of this century. It is very likely that this 33.3 ± 11.7 day prolongation in stratification will accelerate lake deoxygenation with subsequent effects on nutrient mineralization and phosphorus release from lake sediments. Further mis...
The review intends to give an overview on developments, success, results of photosynthetic resear... more The review intends to give an overview on developments, success, results of photosynthetic research and on primary productivity of algae both freshwater and marine with emphasis on more recent discoveries. Methods and techniques are briefly outlined focusing on latest improvements. Light harvesting and carbon acquisition are evaluated as a basis of regional and global primary productivity and algal growth. Thereafter, long-time series, remote sensing and river production are exemplified and linked to the potential effects of climate change. Lastly, the synthesis seeks to put the life achievements of Colin S. Reynolds into context of the subject review.
Background. Poyang Lake is an exceptional system exhibiting a water level change of up to 14 m ev... more Background. Poyang Lake is an exceptional system exhibiting a water level change of up to 14 m every year. In the years 2013 and 2014 water level changes were 8.03 m and 11.22m respectively. The biomass of Anabaena and heterocyst frequency increased in the summers of recent years. Methods. A weekly or bi-weekly monitoring period from June to November 2013 and 2014 was set up to explain the reason for this phenomenon. Results. Anabaena was observed throughout the year. The average relative biomass of Anabaena in the study period was over 40%, being most abundant in summer. The average heterocyst frequency was 0.226% in 2013 and 0.760% in 2014. The SPSS analysis indicated a positive correlation of Anabaena biomass with water temperature and water level and negative one with TN, which is the reason for the increase of heterocyst frequency from 2013 to 2014. It also indicated that heterocyst frequency of Anabaena was positively correlated with water temperature, water level and PO4-P, a...
Aquatic ecosystems are of critical ecological, social and economic importance. Worldwide increase... more Aquatic ecosystems are of critical ecological, social and economic importance. Worldwide increase in their use and anthropogenic pressures alter their health which is essential for the maintenance of water quality, biodiversity, and fishing activities. The European Parliament sets out a framework for managing and protecting water for each main catchment basin at a European level. The aim is to propose objectives to conserve or restore the state of water-bodies into a status that would be considered "good" in development and ecological terms. A key issue in the implementation of the Water Framework Directive is the classification of water-bodies into "quality status" using biological indices. Comparison and classification of water bodies throughout Europe require the improvement and development of new methodologies based upon scientific knowledge. New methods and indices have been proposed for categorizing water bodies into quality status. In this study we took advantage of the long-term data set of phytoplankton abundance and composition sampled in Lake Geneva (France-Switzerland) to test an index formally developed for Austrian lakes. Lake Geneva has suffered from eutrophication in the 80's. Comparisons between the tested and classical indices show that recovery from eutrophication is a long process that could be altered by large scale pressures such as climate change.
This review summarizes winter conditions from six polymictic European shallow lakes. The lakes ra... more This review summarizes winter conditions from six polymictic European shallow lakes. The lakes range from oligotrophic to hyper-eutrophic. Four of the lakes freeze regularly while ice cover is absent or rare in the two others. Ice duration and timing of ice-out are significantly influenced by climate signals in three of the lakes. Winter water temperature remains higher in nonice-covered lakes. No long-term trend in temperature is detectable except for one lake where winter water temperature began to increase in 1986. Secchi depth in winter is equal or greater than summer values in all six lakes indicating relatively better light conditions in winter. Total phosphorus concentration in winter ranges from 10 to 130 µg L-1 , which is equal or lower than summer values and is unrelated to chlorophyll a in five of the sites. Phytoplankton species composition during winter differs largely at the six sites. The winter assemblages largely depend on the trophic level and the conditions during the previous season. Winter chlorophyll a and phytoplankton biomass are usually lower than summer values because of reduced photosynthetic rates. Bacterial production often exceeds primary production. Epipelic algal assemblages tend to proliferate during winter in both ice-covered and non-ice-covered lakes. Primary production is low during winter because of insufficient light. Zooplankton abundances and biomass critically depend on conditions during the previous season and the winter situation and are quite variable from year to year, but their values correlate with the trophic status of the lakes. As a result, winter conditions are important to understand seasonal and annual changes in shallow lakes.
Long-term phytoplankton assemblages in a large shallow Chinese lake, Lake Taihu, were presented u... more Long-term phytoplankton assemblages in a large shallow Chinese lake, Lake Taihu, were presented using the monthly monitoring data from October 1991 to December 1999. Earlier research results (1960, 1981 and 1988) were applied to discuss the different trophic stages of the lake. The species composition in the lake was more closely related to eutrophication level than to lake-size, shallowness, or turbidity. Each summer, a single peak of phytoplankton biovolume appeared in Meiliang Bay. The results of principal components analysis showed a distinct temporal shift in species composition between summer and winter. A clear spatial difference in phytoplankton occurred between Meiliang Bay and the lake centre. Wind speed and direction affected the horizontal distribution of phytoplankton, especially Microcystis, in the lake. Temperature, underwater light climate, nutrients and grazing by zooplankton and by fish were discussed to explain the overwhelming dominance of Microcystis. Four nutri...
Eutrophication: Causes, Consequences and Control, 2013
Ecosystem services are the benefits provided to people by ecosystems and biodiversity. Fresh wate... more Ecosystem services are the benefits provided to people by ecosystems and biodiversity. Fresh water is a ' provisioning' service referring to the human use offresh water for several purposes. The hydrological cycle also sustains inland water ecosystems, including rivers, lakes and wetlands. These ecosystems provide regulating, supporting and cultural services that contribute directly and indirectly to human well-being through recreation, seenie values and fisheries. To maintain ecosystem health or ecosystem integrity, extemal or intemal perturbations must be kept below the carrying capacity. Anthropogenie disturbances offreshwater resources as a consequence oftourism are diverse. In many regions of the world, lakes and ponds in particular are important freshwater habitats providing significant attraction for the public. Impacts to lakes from tourist activities occur directly to the lake water and shoreline, or can affect the water body indirectly through various actions in the catchment. The response of a specific freshwater ecosystem depends on the type of interference as well as the type and size of the lake. Shallow lakes are affected and hence behave differently from deep lakes. Large lakes react in a different way than smalllakes. Impacts are also modified and mediated by the characteristics of the catchment, such as morphology, size, land-use and population structure. Impacts to tourist lakes are classified as direct and indirect effects and are analysed and exemplified.
In this chapter, the quantitative changes of the components of the hydrosphere are analyzed for t... more In this chapter, the quantitative changes of the components of the hydrosphere are analyzed for the period from 1950 to 2010 and then for the period from 2 000 until the end of this century. For the first period, the observed changes are descri- bed by analyzing the time series of snow depth, glacier volu- mes, surface runoff, water temperatures and groundwater tab- les. For the future period from 2010 to 2100, regional climate models are applied in order to provide the input to various hydrological models. In particular, results were selected from the CLM-ECHAM5-A1B and REMO-UBA models, with SRES emission scenarios A2, A1B and B1, as well as the A1B simulation from the ARPEGE-ALADIN and Reg-CM3 from the ENSEMBLES project. Additionally, two scenarios from the 5th IPCC-Assessment Report (RCP2.6 und RCP8.5) were analysed with respect to the impacts on glaciers. The data show that in Austria, since 1980 the snow line has shifted upwards, predominantly in the summer season. This is cons...
Alte Donau nowadays is an eutrophic urban lake within the city of Vienna. Increasing nutrient con... more Alte Donau nowadays is an eutrophic urban lake within the city of Vienna. Increasing nutrient concentrations and massive blooms of cyanobacteria mainly caused by Limnothrix redekei Van Goor and Cylindrospermopsis raciborskii (Wołsz.) Seenayya et Subba Raju were recently registered. As a consequence Secchi depth was significantly reduced especially during the summer season (minimum: 0.25 m). An investigation including water chemistry, phytoplankton, macrophytes, and sediment was initiated in 1993 and extended to metazooplankton, ciliates and bacteria in 1994. The first half of the year 1994 was characterised by relatively clear water and a high diversity of the phytoplankton composition due to flushing of the lake with water of better quality by the end of 1993. Ciliates and metazooplankton held about 10% of the total biomass of all the investigated trophic levels. The vanishing of the remaining macrophytes enlarged the nutrient supply during summer 1994 and favoured the development of cyanobacteria. The high water temperatures which excluded certain zooplankton species, and the inedibility of the filaments further increased the dominance of cyanobacteria. In November, when the algal bloom finally ceased, the highest bacterial numbers of the investigation period occurred. Thereafter, other algal groups, bacteria and metazooplankton gained more importance. Interactions are possible because of close overlap in space and time due to the turbulent mixed conditions of the water body and the change from the macrophyte dominated to the algal dominated stable state. Planned restoration measures must aim to re-establish the previous macrophyte dominated clear-water stage.
One of the key actions identified by the Water Framework Directive (WFD; 2000/60/EC) is to develo... more One of the key actions identified by the Water Framework Directive (WFD; 2000/60/EC) is to develop ecological assessment tools and carry out a European intercalibration (IC) exercise. The aim of the Intercalibration is to ensure that the values assigned by each Member State to the good ecological class boundaries are consistent with the Directive’s generic description of these boundaries and comparable to the boundaries proposed by other MS. In total, 83 lake assessment methods were submitted for the 2nd phase of the WFD intercalibration (2008-2012) and 62 intercalibrated and included in the EC Decision on Intercalibration (EC 2013). The intercalibration was carried out in the 13 Lake Geographical Intercalibration Groups according to the ecoregion and biological quality element. In this report we describe how the intercalibration exercise has been carried out in the Alpine Lake Phytoplankton Intercalibration group
The Ecological Bases for Lake and Reservoir Management, 1999
Recent changes which have been observed at Alte Donau, a shallow urban lake within the city of Vi... more Recent changes which have been observed at Alte Donau, a shallow urban lake within the city of Vienna, have been interpreted as a shift to a new stable state. The former macrophyte-dominated state changed to a turbid state dominated by high biomass of filamentous cyanobacteria, associated with a significant reduction in Secchidepth. Phytoplankton was dominated by the filamentous cyanobacterial species Cylindrospermopsis raciborskii (Wolosz.), Seenayya et Subba Raju and Limnothrix redekei (Van Goor) Meffert. Integrated restoration plans included internal and external measures. Improvements in the catchment aim to minimize the input of nutrients from contaminated groundwater and from storm water and to reduce large numbers of water fowl. Internal restoration measures included water exchange, chemical flocculation and nitrate oxidation of the sediments. Additionally, macrophyte re-colonisation was enhanced through planting. A pelagic predator (Aspius aspius L.) was stocked to reduce bleak (Alburnus alburnus L.), the dominant cyprinid planktivore. Results from the period after water exchange and chemical treatment, showed significant reduction of nutrient and chlorophyll a concentrations. A shift in the phytoplankton species from cyanobacteria towards diatoms and greens was observed. Secchi depth greatly increased. Macrophyte growth became apparent both through re-colonisation, as well as from the planting.
Climate change impacts include such an overwhelming number of facets that the extent of reference... more Climate change impacts include such an overwhelming number of facets that the extent of references is impossible to cover. The selection presented in this review on global warming is presumably subjective, although the author has tried to assemble relevant and/or most recent information. The references specified should be regarded as examples that direct the reader to more information on a specific subject.
In Europe, the effects of global warming are expected to be particularly acute in areas exposed t... more In Europe, the effects of global warming are expected to be particularly acute in areas exposed to a more extreme continental climate. The climate change scenarios summarized in Chapter 2, this volume, suggest that the average summer temperatures in some areas of Central Europe could increase by as much as 6 • C by 2071-2100. The associated projections for the rainfall give even more cause for concern with the reductions in some areas approaching 50% in summer. In this chapter we analyse impacts of changing weather conditions on lakes in Central Europe. Long-term data sets from a number of lakes are used to link measured variables to climate signals. Particular attention is paid to the lakes in the perialpine region which are known to be very sensitive to short-term changes in the weather (Psenner, 2003; Thompson et al., 2005). Here, the topography and the steep orography enhance the water cycle, and result in flooding, debris flows, avalanches, vertical plant migration etc. The Alps also form a barrier to the mass movement of air and are responsible for the sharp climatic divide between Atlantic, Continental and Mediterranean influences. Central Europe is a variously and vaguely defined region. Rather than a physical entity, it is more a reflection of a shared history. The results summarized here are based on the analysis of long-term climatological and limnological data from the countries shown in Fig. 20.1. These include Germany (DE), Poland (PL), the Czech Republic (CZ), Slovakia (SK), Switzerland (CH), Lichtenstein (LI), Austria (AT) and Hungary (HU). The Central European countries are geographically diverse with landforms ranging from the North-German Lowlands, through the Alps to the Hungarian plain. The pannonian plain in the eastern part is also a major climatic 'crossing point' and is affected by the Eastern-European continental, the Western-European oceanic and the Mediterranean influence.
The Impact of Climate Change on European Lakes, 2009
Fig.17.2 An overview of the factors affecting the relationship between climatic forcing and the p... more Fig.17.2 An overview of the factors affecting the relationship between climatic forcing and the physical lake response to this forcing Climate: Spatially and temporally coherent Degree cif spatial coherence deriendson scale (regional, synoptic, hemlspherlc,global) Weather; Local manifestation of climate Air temperature Cloud cover Relative humidity Wind speed
Twenty to fifty years of annual mean deepwater (hypolimnetic) temperature data from twelve deep l... more Twenty to fifty years of annual mean deepwater (hypolimnetic) temperature data from twelve deep lakes spaced across Europe (2u959W to 14u09E, 46u279 to 59u009N) show a high degree of coherence among lakes, particularly within geographic regions. Hypolimnetic temperatures vary between years but increased consistently in all lakes by about 0.1-0.2uC per decade. The observed increase was related to the weather generated by largescale climatic processes over the Atlantic. To be effective, the climatic signal from the North Atlantic Oscillation (NAO) must affect deep lakes in spring before the onset of thermal stratification. The most consistent predictor of hypolimnetic temperature is the mean NAO index for January-May (NAO J-M), which explains 22-63% of the interannual variation in deepwater temperature in 10 of the 12 lakes. The two exceptions are remote, less windexposed alpine valley lakes. In four of the deepest lakes, the climate signal fades with depth. The projected hypolimnetic temperature increase of approximately 1uC in 100 yr, obtained using a conservative approach, seems small. Effects on mixing conditions, thermal stability, or the replenishment of oxygen to deep waters result in accumulation of nutrients, which in turn will affect the trophic status and the food web.
One of the most important physical characteristics driving lifecycle events in lakes is stratific... more One of the most important physical characteristics driving lifecycle events in lakes is stratification. Already subtle variations in the timing of stratification onset and break-up (phenology) are known to have major ecological effects, mainly by determining the availability of light, nutrients, carbon and oxygen to organisms. Despite its ecological importance, historic and future global changes in stratification phenology are unknown. Here, we used a lake-climate model ensemble and long-term observational data, to investigate changes in lake stratification phenology across the Northern Hemisphere from 1901 to 2099. Under the high-greenhouse-gas-emission scenario, stratification will begin 22.0 ± 7.0 days earlier and end 11.3 ± 4.7 days later by the end of this century. It is very likely that this 33.3 ± 11.7 day prolongation in stratification will accelerate lake deoxygenation with subsequent effects on nutrient mineralization and phosphorus release from lake sediments. Further mis...
The review intends to give an overview on developments, success, results of photosynthetic resear... more The review intends to give an overview on developments, success, results of photosynthetic research and on primary productivity of algae both freshwater and marine with emphasis on more recent discoveries. Methods and techniques are briefly outlined focusing on latest improvements. Light harvesting and carbon acquisition are evaluated as a basis of regional and global primary productivity and algal growth. Thereafter, long-time series, remote sensing and river production are exemplified and linked to the potential effects of climate change. Lastly, the synthesis seeks to put the life achievements of Colin S. Reynolds into context of the subject review.
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Papers by Martin Dokulil