Brigitte Nixdorf

Brandenburgische Technische Universität Cottbus, Kottbus, Brandenburg, Germany

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Publications (68)62.97 Total impact

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    ABSTRACT: Abstract Process Understanding as Basis for Water Body Management – Case Studies on Limitation, Competition, Water Body Structure and Food Web Control A precise understanding of the processes that take place in water bodies is an important precondition for successful water body management schemes. On the basis of recent examples, the complexity and seasonality of controlling the trophic status of standing water bodies is described from different angles. The limitation of phytoplankton development by nitrogen (N) and phosphorus (P) as well as further factors are seasonal in character and depend on the type of lake; this must be taken into account when setting target values. Long-term data show that the intended repopulation of lakes with macrophytes can take a long time, even after drastic measures were taken to reduce P levels. Influencing the food web through fish stocking is a still underestimated potential tool for controlling water quality. An analysis of the case studies shows that the objective of nutrient reduction must be a phosphorus-limited status, since this offers the best opportunities for the practical implementation of therapy measures for lakes. The results confirm that in addition to P reduction, there are also other practical tools that will lead to a clear improvement in water quality if used consistently. Key words: trophic level, phytoplankton, nutrients, macrophytes, therapy measures for lakes, fish stocking, standing water bodies Language: German Zusammenfassung Das genaue Verständnis der in den Gewässern ablaufenden Prozesse ist eine wichtige Voraussetzung für erfolgreiche Bewirtschaftungsmaßnahmen. Anhand von aktuellen Fallbeispielen wird die Komplexität und Saisonalität der Trophiesteuerung von Standgewässern unter verschiedenen Aspekten vorgestellt. Die Limitation der Phytoplanktonentwicklung durch Stickstoff (N) und Phosphor (P) sowie weiterer Faktoren ist saisonal geprägt und hängt vom Seetyp ab, was bei der Zielwertfestlegung zu berücksichtigen ist. Langzeitdaten zeigen, dass die gewünschte Wiederbesiedlung mit Makrophyten in Seen auch nach drastischen Maßnahmen zur Verringerung der P-Konzentrationen lange dauern kann. Ein immer noch unterschätztes Potenzial zur Steuerung der Wasserqualität bietet die Beeinflussung des Nahrungsnetzes über den Fischbesatz. Die Analyse der Fallbeispiele zeigt, dass das Ziel von Nährstoffreduzierungen ein P-limitierter Zustand sein sollte, da er für praktische Umsetzungen in der Seentherapie die günstigsten Voraussetzungen bietet. Die Ergebnisse belegen, dass neben der P-Verminderung weitere praxistaugliche Werkzeuge existieren, die bei konsequenter Umsetzung deutliche qualitätsverbessernde Effekte zur Folge haben. Schlagwörter: Trophie, Phytoplankton, Nährstoffe, Makrophyten, Seentherapie, Fischbesatz, stehende Gewässer DOI: 10.3243/kwe2013.12.001
    Wasserwirtschaft 02/2013; 60:693-701. · 0.09 Impact Factor
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    ABSTRACT: Based on measured and calculated long-term data on external phosphorus (P) load (1920–2009), hypolimnetic P accumulation and trophic parameters for the dimictic Lake Scharmützelsee, we aimed to identify factors which cause variable P net sedimentation and the importance of internal P loading for different time periods especially focusing on non-steady state after abrupt external load reduction in 1988. P retention (R) decreased from 0.85 during the high external P loading (0.37 g m–2 a–1) phase (1950–1988) to 0.71 during the following transient phase, and increased to 0.81 for the present recovery phase (0.17 g m–2 a–1) beginning in 2003. Mean net sedimentation coefficients for the same periods were 0.47, 0.22 and 0.30. Our results show that a) empirical models overestimate R during the high loading phase and underestimate R during the transient phase after load reduction, and b) the application of simple one-box models which assume that a portion of in-lake P stock is retained requires the consideration of the variability of the net sedimentation coefficient. We identified multiple reasons for variable gross sedimentation (e.g., particle trapping in the elongated lake; efficient accumulation of sewage P) as well as release of P (delayed release of mobile P from sediment; changes in plant colonization and food webs), so that their relation (net sedimentation) varies. Despite a new equilibrium reached in 2003, it is still unclear when the lake will reach mesotrophic reference conditions and a good ecological status. Historical data and elevated Cl– concentration (22 mg L–1) indicate that P import from sewage contaminated groundwater still continues, so that the mean in-lake P concentration is still too high (53 µg L–1), and biological structures have not fully recovered yet. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Internationale Revue der gesamten Hydrobiologie und Hydrographie 11/2011; 96(5):599 - 621.
  • Marion Martienssen, Jörg Böllmann, Brigitte Nixdorf
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    ABSTRACT: Im Verbundprojekt NITROLIMIT werden in den prozessorientierten Teilprojekten Stickstoffeinträge durch N-Fixierung und Ammoniumfreisetzung aus den Sedimenten sowie die Kapazitäten für Nitrifikation, Denitrifikation und Anammox durch Laboruntersuchungen und Bilanzierungsansätze erfasst. Des Weiteren werden die Zellzahlen der dazugehörigen Spezialisten (Nitrifikanten und Denitrifikanten, Planctomycetales) mittels kultivierungsabhängiger und gentechnischer Methoden bestimmt. Die Resultate der Laboruntersuchungen dienen als Grundlage für eine modellgestützte Bilanzierung der tatsächlichen Stickstoffumsätze unter Berücksichtigung der jahreszeitlichen Schwankungen weiterer Prozessgrößen wie C-Angebot, Temperatur und Sauerstoffgehalt im Gewässer. Im Mittelpunkt der Untersuchungen stehen ein mesotropher dimiktischer (Scharmützelsee) und ein eutropher sehr flacher See (Langer See), ein mitteltiefer Flusssee (Müggelsee) und das Flussseensystem Untere Havel. Auswertungen von Stickstoffumsatzraten aus langjährigen Datenreihen zu den Gewässern belegen saisonale Limitationsereignisse auch für Stickstoff in den unterschiedlichen Gewässertypen in den Sommermonaten. Erste vorläufige Bilanzierungen auf der Basis von Änderungsraten der unterschiedlichen N-Komponenten in den Gewässern ergaben Umsatzraten von bis zu 20 µgN L-1 d-1 , wobei die einzelnen N-Umsatzprozesse mit diesem Ansatz nicht quantitativ getrennt werden können. Erste modellbasierte Analysen der Nitrifikations- und Denitrifikationskapazität mittels reaktionskinetischer Betrachtungen lieferten Umsatzraten in Abhängigkeit von der Kohlenstoff- und Sauerstoffkonzentration und der Temperatur zwischen 1,3 und 170 µgN L-1 d-1 für die Nitrifikation und 0,5 – 170 µgN L-1 d-1 für die Denitrifikation. Diese Ergebnisse werden durch Messungen aus der Vegetationsperiode 2011 ergänzt und mit den Kalkulationen der Umsatzkinetiken und Zellzahlen aus den Laborversuchen verglichen und diskutiert.
    Jahrestagung der DGL 2011, Weihenstephan; 09/2011
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    ABSTRACT: Im Verbundprojekt NITROLIMIT werden in den prozessorientierten Teilprojekten Stickstoffeinträge durch N-Fixierung und Ammoniumfreisetzung aus den Sedimenten sowie die Kapazitäten für Nitrifikation, Denitrifikation und Anammox durch Laboruntersuchungen und Bilanzierungsansätze erfasst. Des Weiteren werden die Zellzahlen der dazugehörigen Spezialisten (Nitrifikanten und Denitrifikanten, Planctomycetales) mittels kultivierungsabhängiger und gentechnischer Methoden bestimmt. Die Resultate der Laboruntersuchungen dienen als Grundlage für eine modellgestützte Bilanzierung der tatsächlichen Stickstoffumsätze unter Berücksichtigung der jahreszeitlichen Schwankungen weiterer Prozessgrößen wie C-Angebot, Temperatur und Sauerstoffgehalt im Gewässer. Im Mittelpunkt der Untersuchungen stehen ein mesotropher dimiktischer (Scharmützelsee) und ein eutropher sehr flacher See (Langer See), ein mitteltiefer Flusssee (Müggelsee) und das Flussseensystem Untere Havel. Auswertungen von Stickstoffumsatzraten aus langjährigen Datenreihen zu den Gewässern belegen saisonale Limitationsereignisse auch für Stickstoff in den unterschiedlichen Gewässertypen in den Sommermonaten. Erste vorläufige Bilanzierungen auf der Basis von Änderungsraten der unterschiedlichen N-Komponenten in den Gewässern ergaben Umsatzraten von bis zu 20 µgN L-1 d-1 , wobei die einzelnen N-Umsatzprozesse mit diesem Ansatz nicht quantitativ getrennt werden können. Erste modellbasierte Analysen der Nitrifikations- und Denitrifikationskapazität mittels reaktionskinetischer Betrachtungen lieferten Umsatzraten in Abhängigkeit von der Kohlenstoff- und Sauerstoffkonzentration und der Temperatur zwischen 1,3 und 170 µgN L-1 d-1 für die Nitrifikation und 0,5 – 170 µgN L-1 d-1 für die Denitrifikation. Diese Ergebnisse werden durch Messungen aus der Vegetationsperiode 2011 ergänzt und mit den Kalkulationen der Umsatzkinetiken und Zellzahlen aus den Laborversuchen verglichen und diskutiert.
    Jahrestagung der DGL 2011, Weihenstephan; 09/2011
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    ABSTRACT: Cyanobacteria of the order Nostocales found in lakes in temperate regions are generally assumed to benefit from climate change. To predict their future development under varying environmental conditions, we developed a mathematical model that simulates their entire life cycle. Cylindrospermopsis raciborskii, a tropical species which spread to the northern temperate zone during the last decades, was used as the model organism. We calibrated and validated the model using a 13-year data set on the species' population dynamics gathered in a shallow lake in northern Germany. The predicted values were consistent with the observed data. We used sensitivity studies and Hasse diagrams based on partial order theory to rank the impact of different model parameters on life cycle dynamics. Our results show that the seasonal dynamics of C. raciborskii are mainly determined by the optimum growth temperature of its vegetative cells. The dynamics of pelagic populations in the water and akinete populations (resting stages) in the sediment is highly dependent on lake water temperature and underwater light intensity and, thus, on climatic conditions. Therefore, any future increase in lake water temperature will presumably lead to an increase in the size of C. raciborskii populations in particular and of Nostocales populations in general. (c) 2010 Elsevier Ltd. All rights reserved.
    Environmental Modelling and Software 05/2011; 26:669-677. · 3.48 Impact Factor
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    ABSTRACT: Some tropical cyanobacteria have spread to temperate freshwaters during the last decades. To evaluate their further development in temperate lakes, we studied the temperature- and light-dependent growth of three invasive (Cylindrospermopsis raciborskii, Anabaena bergii and Aphanizomenon aphanizomenoides) and three native (Aphanizomenon gracile, Aphanizomenon flos-aquae and Anabaena macrospora) cyanobacterial species (Nostocales) from German lakes. We also included one potentially invasive (Aphanizomenon ovalisporum) Nostocales species. We conducted semi-continuous culture experiments and a microcosm experiment along a natural light gradient. Temperature data were used to design a model to simulate the development of selected species according to three temperature scenarios (past, present and future). Native species had significantly higher growth rates than invasive species and the potential invader A. ovalisporum at low temperatures (< 10 degrees C), while the opposite was true at high temperatures (>= 35 degrees C). Maximum growth rates of A. ovalisporum, A. aphanizomenoides and C. raciborskii were clearly higher than those of A. bergii and the native species. Regarding light-dependent growth, significant differences were found between single species but not between all native and invasive species. The model simulation demonstrates a shift in dominance from the native A. gracile in the historic scenario to C. raciborskii populations in the future scenario, in which also the potential invader A. ovalisporum is able to establish populations in temperate lakes. Our findings suggest that any further temperature increase would promote the growth and development of Nostocales species in general, and that of the invasive species in particular, and would enable a more northward expansion of A. ovalisporum.
    Journal of Plankton Research 07/2010; 32:1009-1021. · 2.44 Impact Factor
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    Brigitte Nixdorf, Wilfried Uhlmann, Dieter Lessmann
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    ABSTRACT: About one third of several hundred mining lakes in Eastern Germany are highly acidified, and there is a need to restore them to neutral conditions because they constitute an environmental hazard for water resources and downstream environments. The aim of this study is to evaluate the efficiency of three different acid pit lake water remediation treatments: dilution with alkaline (river) water, limestone treatment and biological neutralization by organic carbon-driven alkalinity generation. The efficiency is evaluated for the acidic mining lake Grünewalder Lauch by adjusting input values into a geochemical model and making future projections. Current approaches, such as flooding with neutral surface water or extensive liming, are not suitable for many lakes because of a limited supply of alkaline water or high lime immobilizing potential of Fe- and Al-rich water in acidic lakes, respectively. Further treatment methods are, therefore, designed to combine water supply and biological measures with the management of water quality by the application of in-lake microbial processes. These processes are focused on the metabolic response of aquatic ecosystems to nutrient enrichment (enhancement of primary production and thereby organic carbon supply) and the microbial decomposition of organic matter and their effects on the gain or loss of alkalinity.The results and comparisons of different neutralization measures will be generalized by the application of hydrogeochemical models for alkalinity production showinga)the long term efficiency of the measures, depending on carbon turnover at the sediment/water interface,b)the development of bicarbonate buffering capacity as a consequence of biological measures,c)the importance of pyrite formation instead of FeS.
    Limnologica. 01/2010; 40(2):167-174.
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    Deutsche Gesellschaft für Limnologie (DGL) Erweiterte Zusammenfassungen der Jahrestagung 2009 (Oldenburg); 01/2010
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    ABSTRACT: Feedback between submerged macrophytes and water transparency stabilizing the clear, macrophyte-dominated regime has been described so far for shallow lakes. Based on data of total phosphorus (TP) concentrations, underwater light supply, phytoplankton and submerged macrophyte abundance from narrow, stratified Lake Scharmützelsee (mean depth: 9 m, retention time: 16 yr) of the period 1994-2006 we hypothesize that submerged macrophytes may influence transparency and trophic state in deep lakes. The lake was characterized by summer epilimnion TP concentrations of 38 to 57 mug L(-1), turbid water due to mass development of cyanobacteria, and low abundance of few submerged macrophyte species until 2003. Thereafter, a sudden increase in water transparency was followed by a rapid submerged macrophyte colonization of the littoral down to about 5 m depth corresponding to the depth of a light supply of 3 E m(-2) d(-1). Initially, this recolonization was probably a consequence of decreased turbidity. We argue that the increase of submerged macrophyte coverage from < 10% in 1994 to 2003 to about 24% in 2005-2006 has contributed to the stabilization of the clear-water regime during the subsequent years. This is supported by the fact that earlier shifts to clear-water regimes in 1994 and 2000 without a significant spread of submerged macrophytes were not stable. We discuss potential mechanisms that may have resulted in a positive effect of plants on transparency such as P uptake and immobilization by the dominant rootless macrophyte species Nitellopsis obtusa and Ceratophyllum demersum and other macrophyte-related mechanisms such as increased zooplankton grazing and allelopathy.
    Journal of Environmental Quality 01/2010; 39(2):725-33. · 2.35 Impact Factor
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    ABSTRACT: Süßwasserseen haben als ökosysteme und Lebensraum für Pflanzen und Tiere eine herausragende Bedeutung für die Artenvielfalt auf der Erde und prägen als Landschaftselemente unsere natürliche Umwelt. Seen fungieren als natürliche Stoffsenken, vor allem für Kohlenstoff und Nährstoffe, aber auch als Senken für in ihren Einzugsgebieten emittierte gelöste und feste Schadstoffe. Darüber hinaus ist Wasser eine wichtige Naturressource. Süßwasserseen stellen in den meisten Regionen der Erde lebenswichtige Quellen für die Versorgung mit Trinkwasser und tierischem Eiweiß (Fischfang) dar. Sie dienen als Wasserspeicher für die landwirtschaftliche und industrielle Nutzung. Auch für Erholungsaktivitäten des Menschen kommt ihnen eine große Bedeutung zu.
    08/2009: pages 125-151;
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    ABSTRACT: Akinete formation enables cyanobacteria of the order Nostocales to survive adverse conditions (e.g. winters in temperate zones) and is assumed to be a prerequisite for the invasion of tropical species like Cylindrospermopsis raciborskii into the temperate zones. We chose C. raciborskii for a 4-year study of the seasonal patterns of all life cycle stages in the pelagic and benthic zones of a shallow eutrophic lake in NE Germany. Akinete production started when C. raciborskii populations reached maximum cell abundance and water temperatures started to decrease, resulting in an increase in the number of akinetes at the sediment surface. The number of akinetes on the sediment (inoculum for the next year) was population size dependent. It decreased slightly in winter but dropped sharply from end of April to June/July, reflective of germination. Thus, germination started at temperatures of about 13°C. Typically, first filaments appeared in June and populations peaked in August. However, the size of the population in summer was not determined by the size of the inoculum. Consequently, it is assumed that population development is determined by growth conditions and loss processes after germination.
    01/2009;
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    ABSTRACT: Cylindrospermopsin (CYN) is a potent hepatotoxin produced by different cyanobacteria of the order Nostocales. Questions of major concern are: which species produce CYN, which are the seasonal patterns of CYN dynamics and how are they regulated? Therefore, we studied for the first time the seasonal dynamics of particulate and dissolved CYN concentrations, cyanobacterial abundance and environmental factors in two German lakes over 2 years. Total CYN reached maximum concentrations of 0.34 and 1.80 microg L(-1) in Melangsee and Langer See, respectively. In both lakes, maxima of the dissolved CYN fraction occurred later in the season than those of the particulate fraction, and it reached higher concentrations. This indicates that CYN is poorly decomposed and accumulates in the water. The cyanobacterial community in both lakes included several potentially CYN-producing species that did not correlate with CYN concentrations. Significant correlations between the particulate CYN concentrations and species biovolume were only found for Aphanizomenon gracile (r(s)=0.803) in Langer See indicating that this species is a CYN producer. Different correlations of CYN with abiotic factors in the two lakes indicate the presence of further undetected CYN producers as well as different regulation mechanisms of their dynamics and the variability of CYN.
    Toxicon 09/2008; 52(6):677-86. · 2.92 Impact Factor
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    ABSTRACT: This chapter describes the revised method to assess lakes based on phytoplankton in accordance with the proposal by Mischke et al. (2008) and corresponds to Chapter 3 of the German report. The German phytoplankton-based assessment system for lakes yields a multi-metric index value, the Phyto-See-Index (PSI), and differentiates between different lake types. It classifies water bodies into one of five status classes in accordance with the Water Framework Directive (WFD). The PSI consists of three mandatory metrics: "biomass", "algal classes" and the "Phytoplankton-Taxa-Seen-Index" (PTSI). A step-by-step calculation of the German PSI is included. The first proposal (Nixdorf et al. 2005b) was extensively modified in response to the outcome of both a national exercise and the European intercalibration exercise. This chapter will serve as the basis for a final publication in the form of a manual on the German system for phytoplankton-based assessment of lakes after further improvement.
    03/2008: pages 117-146; , ISBN: 978-3-940471-06-2
  • Brigitte Nixdorf, Atis Rektins, Ute Mischke
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    ABSTRACT: Water protection policy of the European Union (EU) dates back to 1970s, especially to Paris Summit in 1972, where commitment was made to introduce common EU wide environmental policy that included protection of water resources (European Parliament 1972). Since then, several water quality acts have been passed, mostly regulating water pollution. As environmental issues took more important place in the political agenda and EU water policy was rather fragmented, consisting of many complex individual and fragmented regulations, the European Commission (EC) stressed out the need for an integrated approach to water resources covering both the quantitative and qualitative aspects of the policy, management of both surface water and groundwater, environmental protection and the links with other policies (EC 1994). The Water Framework Directive (WFD), proposed in 1994, was finally adopted in 2000. It applies to all water in the natural environment - rivers, lakes, estuaries and coastal waters as well as groundwater.
    12/2007: pages 301-314;
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    ABSTRACT: The cyanobacterial toxin cylindrospermopsin (CYN) is widely distributed in German lakes, but volumetric data for risk assessment are lacking and it is unclear which cyanobacterial species produce CYN in Europe. We therefore analyzed CYN concentration and cyanobacterial composition of 21 German lakes in 2005. CYN was detected in 19 lakes (102 of 115 samples). In total, 45 samples contained particulate CYN only, and 57 contained both dissolved and particulate CYN. The concentrations were 0.002-0.484 microg L(-1) for particulate CYN and 0.08-11.75 microg L(-1) for dissolved CYN with a maximum of 12.1 microg L(-1) total CYN. A drinking water guideline value of 1 microg L(-1) proposed by Humpage and Falconer [2003. Oral toxicity of the cyanobacterial toxin CYN in male Swiss albino mice: determination of no observed adverse effect level for deriving a drinking water guideline value. Environ. Toxicol. 18, 94-103] was exceeded in 18 samples from eight lakes due to high concentrations of dissolved CYN. CYN occurrence in the German lakes could not be ascribed to the three known CYN-producing species Cylindrospermopsis raciborskii, Anabaena bergii and Aphanizomenon flos-aquae, which were detected in some lakes in low abundances. The highest correlation coefficients were observed between particulate CYN and the native Aphanizomenon gracile. It occurred in 98 CYN-positive samples, was the most abundant Nostocales and was the only Nostocales in five samples. This indicates that A. gracile is a potential CYN producer in German lakes.
    Toxicon 12/2007; 50(6):800-9. · 2.92 Impact Factor
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    ABSTRACT: Cylindrospermopsis raciborskii, an invasive freshwater cyanobacterium, originated from the tropics but has spread to temperate zones over the last few decades. Its northernmost populations in Europe occur in North German lakes. How such dramatic changes in its biogeography are possible and how its population dynamics in the newly invaded habitats are regulated are still unexplained. We therefore conducted a long-term (1993-2005) study of two German lakes to elucidate the mechanisms behind C. raciborskii population dynamics and to identify the abiotic constraints on its development. Our data revealed that pelagic populations of C. raciborskii thrived for three months during the summer, contributing up to 23% of the total cyanobacteria biovolume. Population sizes varied greatly between years without exhibiting any distinct long-term trends. In the annual lifecycle, C. raciborskii filaments emerged in the pelagic habitat when the temperature rose above 15-17 degrees C. At that time, mean photosynthetically active radiation in the mixed water column (I (mix)) overstepped its maximum. Rates of population net increase were highest at the beginning of the season (0.15-0.28 day(-1)), declined continuously over time, and were significantly positively correlated with I (mix). This indicates that the onset of the pelagic population is temperature-mediated and that I (mix) controls its growth. Since I (mix) peaks before the population onset, the time of germination is of crucial importance for successful development. To test this hypothesis, we designed a model to simulate pelagic population size, starting at different dates in the annual cycle. Moving the population onset forward by 30 days resulted in a doubling of the population size. We therefore conclude that an earlier rise in water temperature associated with climate change has promoted the spread of C. raciborskii to the temperate zone. Earlier warming permits earlier germination, thereby shifting the pelagic populations to a phase with higher I (mix), which advances growth and the population establishment.
    Oecologia 07/2007; 152(3):473-84. · 3.01 Impact Factor
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    ABSTRACT: The frequent occurrence of the cyanobacterial toxin cylindrospermopsin (CYN) in the (sub)tropics has been largely associated with cyanobacteria of the order Nostocales of tropical origin, in particular Cylindrospermopsis raciborskii. C. raciborskii is currently observed to spread northwards into temperate climatic zones. In addition, further cyanobacteria of the order Nostocales typically inhabiting water bodies in temperate regions are being identified as CYN-producers. Therefore, data on the distribution of CYN in temperate regions are necessary for a first assessment of potential risks due to CYN in water used for drinking and recreation. A total of 127 lakes situated in the north-eastern part of Germany were investigated in 2004 for the presence of the toxin CYN and the phytoplankton composition. The toxin could be detected in half of the lakes (n = 63) and in half of 165 samples (n = 88). Concentrations reached up to 73.2 microg CYN/g DW. CYN thus proved more widely distributed than previously demonstrated. The analyses of phytoplankton data suggest Aphanizomenon sp. and Anabaena sp. as important CYN producers in Germany, and confirm recent findings of Aphanizomenon flos-aquae as CYN-producing species frequently inhabiting water bodies in temperate climatic regions. The data shown here suggest that CYN may be an important cyanobacterial toxin in German water bodies and that further data are needed to assess this.
    Environmental Toxicology 03/2007; 22(1):26-32. · 2.71 Impact Factor
  • Horst Behrendt, Brigitte Nixdorf
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    ABSTRACT: The balance of phytoplankton biomass was studied during spring and early summer 1986 and 1987 in Lake Müggelsee, a eutrophic polymictic lake. It is assessed as the result of biomass changes, gross primary production (14C-method) and physiological or internal and ecological or external losses. Biomass changes, primary production, grazing, dark carbon losses and exudation were estimated from in situ measurements. The remaining light carbon losses and net sedimentation were calculated from the phytoplankton balance of the lake. On average the physiological losses of algae ranged between 80.5 of primary production in 1986 and 72% in 1987. Dark carbon losses by respiration ranged between 15 and 20%, and grazing losses between 24.5 and 21.9% of gross primary production in 1986 and 1987, respectively. The remaining 16.6 and 23.6% of primary production which were lost in 1986 and 1987, respectively, are mainly attributed to sedimentation.
    Internationale Revue der gesamten Hydrobiologie und Hydrographie 01/2007; 78(3):439 - 458.
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    ABSTRACT: Annual changes of rotifers, copepods, cladocerans, the ciliate Epistylis rotans, and larvae of Dreissena polymorpha were analysed for the period 1908–1990. Though food resources increased 6–10 fold in the course of eutrophication, only rotifers and Epistylis increased accordingly. Probably as a result of increased predation pressure crustaceans increased only twice.The seasonal pattern of metazoans and protozoans (flagellates, sarcodines, ciliates) were analysed for 12 and 3 years, resp. During winter and spring, large heterotrophic flagellates and ciliates dominated the zooplankton and were responsible for a pronounced - formerly underestimated - grazing pressure on phytoplankton. In early summer, metazoan filter-feeders were often able to cause a significant reduction of phyto- and protozooplankton. However, during some years, phytoplankton declined in the absence of a pronounced grazing pressure. Field data and experiments revealed that predators were able to regulate the density of cladocerans in early summer (mainly cyclopoids) and summer (mainly Leptodora, smelt and fish juveniles).
    Internationale Revue der gesamten Hydrobiologie und Hydrographie 01/2007; 78(3):379 - 402.
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    ABSTRACT: The influence of turbulence induced mixing on phytoplankton metabolic processes was investigated by hydrophysical and biological measurements in the eutrophic shallow lake Großer Müggelsee (mean depth = 4.9 m). To trace spatial and temporal changes in the mixing depth, high resolution temperature profiles were recorded and analysed.The vertical transport of algae in the mixed layer was simulated by the lift method, which allows an adjustment of the depth and the velocity of particle movement in a wide range (0.5-10 cm, 0.03–3 cm · s−1). The results of this dynamic incubation were compared with those of the conventional static incubation.In general, turbulence induced mixing enhances the areal daily primary production. Net oxygen production in cycled bottles is increased up to three times compared to the areal O2-release of algae which were incubated at a fixed position. This was proved particularly during afternoon incubation indicating the increasing importance of mixing during the course of a day. Changes in the mixing depth have only weak influence on primary production. There is a tendency towards higher O2-production as the mixing depth increases. Remarkable diurnal changes were observed in community respiration and compensation depth. Furthermore, the influence of photoinhibition, O2-saturation of the lake water and the diurnal changes in Chl a-concentration on primary production were measured and discussed.
    Internationale Revue der gesamten Hydrobiologie und Hydrographie 01/2007; 77(3):349 - 360.

Publication Stats

838 Citations
62.97 Total Impact Points

Institutions

  • 1993–2011
    • Brandenburgische Technische Universität Cottbus
      • Department of Freshwater Conservation
      Kottbus, Brandenburg, Germany
  • 2002–2010
    • Leibniz-Institute of Freshwater Ecology and Inland Fisheries
      • Department of Ecohydrology
      Berlín, Berlin, Germany