@phdthesis{Baptista2012, author = {Baptista, Melissa}, title = {Phytoplankton succession and diversity-productivity relation in German and Brazilian shallow lakes}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-24386}, school = {BTU Cottbus - Senftenberg}, year = {2012}, abstract = {Phytoplankton succession linked to productivity-diversity relationship at steady-state/non steady state conditions, mixing events as predominant disturbance in sense of Connell (1978) and influence of conditional differentiation (temperature) on phytoplankton diversity were investigated. Water samples were taken two times a week in 4 German shallow lakes in Brandenbug region (Melangsee, Petersdorfer See, Wolziger See, and Langer See) from 2007 to 2010 and in 2009/2010 during cold and rainy season in a Brazilian coastal lagoon Peri. A comparison between literature data from 4 Brazilian lakes, in order to investigate the influence of temperature on diversity and dynamic of phytoplankton species was also done. The cyanobacterial species dominated all studied lakes and the mixing had a positive effect on the supremacy of this group in tropical lakes. The high biovolume of cyanobacteria contributed to the achievement of steady state conditions in sense of Sommer et al. (1993) during consecutive periods in Petersdorfer See and in Peri lagoon practically during all phases. The monodominance of Cylindrospermopsis raciborskii was observed in warm water, under no stratification regime. Oscillatoriales of group S1 (Reynolds 2002), represented by Limnothrix redekei and Pseudanabaena limnetica, typical in turbid mixed layers and with high nitrogen affinity, were typical in Petersdorfer See. In Melangsee, steady state was observed during colder periods under dominance of Bacillariophyceae and Chrysophyceae. Lower diversity coincided with steady state conditions and higher values of resource use efficiency (RUE), while higher diversity occurred mainly at transitional state during the spring in temperate lakes, supporting the non-equilibrium concept (Hutchinson 1961) at lower RUE values. Higher biovolume occurred mainly during the late summer in temperate lakes under dominance of cyanobacteria, and/or at steady state. Concerning the temporal variation of phytoplankton, the highest peak of species richness preceded the resource use efficiency, suggesting the productivity as consequence of diversity. The richness was much higher in temperate shallow lakes, which were more similar to each other in terms of seasonality, species number and biovolume. A positive correlation between richness and biovolume of temperate lakes was found and the opposite was observed in tropical lakes. The biovolume and richness in tropical lakes were more variable and in temperate lakes presented higher richness at intermediate level of biovolume (annual mean from 10 to 18 mm3/l). Low level of biodiversity allows an ecosystem to function under constant conditions, but a greater biodiversity occurred in fluctuating environments.}, subject = {Brandenburg; Brasilien; Flachsee; Phytoplankton; {\"O}kosystem; Phytoplanktondiversit{\"a}t; Prim{\"a}rproduktion; Phytoplanktonsukzession; Paradoxon des Phytoplankton; Steady-state; Phytoplankton diversity; Succession; Primary productivity; Paradox of phytoplankton}, language = {en} } @techreport{OPUS4-4019, type = {Working Paper}, title = {Positionspapier des Projekts NITROLIMIT - Stickstofflimitation in Binnengew{\"a}ssern - Ist Stickstoffreduktion {\"o}kologisch sinnvoll und wirtschaftlich vertretbar? - Ergebnisse, Schlussfolgerungen, Empfehlungen}, editor = {Wiedner, Claudia and Schlief, Jeanette}, organization = {Projekt NITROLIMIT c/o Brandenburgische Technische Universit{\"a}t Cottbus, Lehrstuhl Gew{\"a}sserschutz, Forschungsstelle Bad Saarow}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-40197}, year = {2016}, abstract = {Das Positionspapier stellt die wichtigsten Ergebnisse des NITROLIMIT Projekts f{\"u}r Fachkollegen aus Wissenschaft und Praxis sowie f{\"u}r alle, die sich f{\"u}r Gew{\"a}sser{\"o}kologie interessieren, kompakt zusammen. Aufgrund der K{\"u}rze k{\"o}nnen nicht alle Teilergebnisse, methodischen Details oder ein kompletter Literatur{\"u}berblick gegeben werden. Eine ausf{\"u}hrliche Darstellung aller Teilstudien ist jedoch in den Abschlussberichten von NITROLIMIT I und NITROLIMIT II zu finden. Zudem wurden ausgew{\"a}hlte Ergebnisse in Form von Diskussionspapieren und wissenschaftlichen Publikationen bereits ver{\"o}ffentlicht. Eine komplette Publikationsliste ist ab Seite 44 zu finden. Die Verantwortung f{\"u}r den Inhalt der einzelnen Kapitel des Positionspapiers liegt bei den Autoren.}, subject = {Stickstoff; Gew{\"a}sserschutz; Stickstoff}, language = {de} } @inproceedings{OPUS4-1829, title = {Proceedings of the Workshop "Pollution Monitoring in the Upper Course of the Lerma River and Application of Clean Technologies in Water Treatment", 17th and 18th February 2009 at the Instituto Nacional de Investigaciones Nucleares (ININ), Mexico-City}, isbn = {978-3-940471-14-7}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-18954}, year = {2010}, abstract = {Rapidly developing countries are facing severe environmental problems at an extent that industrialized countries did not have to solve in comparable periods. Freshwaters belong to the ecosystems with the most severe impacts despite they are one of the most vital resources. The Lerma River is one example of a heavily degraded freshwater ecosystem in the rapidly developing country of Mexico. A number of NGOs and governmental institutions have made great efforts to elaborate strategies for the restoration and rehabilitation of the river system during the last years. Scientists from different disciplines and institutions met for a workshop at ININ in February 2009 to discuss the actual degradation of the upper Lerma River and argue about solutions for its sustainable restoration. This also included the presentation and discussion of new technologies that are currently in an experimental stage, but have the potential to solve different river pollution problems in the near future.}, subject = {Gew{\"a}sserschutz; Fließgew{\"a}sserrestaurierung; Schwellenl{\"a}nder; Bioremediation; Freshwater conservation; Running water restoration; Rapidly developing countries; Bioremediation}, language = {mul} } @phdthesis{MendozaLera2015, author = {Mendoza-Lera, Clara}, title = {Reciprocal influences of microbial community and hydrogeomorphology in sandy streambeds}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-35175}, school = {BTU Cottbus - Senftenberg}, year = {2015}, abstract = {The main goal of this dissertation was to explore the interactions between the hydrogeomorphology of the streambed in sandy lowland low-order streams and the microbial community inhabiting it. In particular, (i) the influence of the vertical water exchange across the streambed and (ii) of the sediment transport on the function and structure of the streambed microbial community, (iii) and the potential of the microbial community to influence these physical factors were explored. The influences were studied with a model system approach (micro- and mesocosms). Firstly, I examined the significance of vertical water exchange across the streambed for the microbial community. I determined the differences in the microbial community structure and function associated with sediments of differing grain sizes. The grain sizes differed in surface-to-volume ratio and hydraulic conductivity. The results revealed vertical water exchange as the major factor for the structure and function of the microbial community. Secondly, I studied the ability of the microbial community to influence the vertical water exchange across two sandy streambeds: leveled and rippled. My results showed that the microbial community can reduce and even block the vertical water exchange by reducing pore space with gas bubbles formed due to high primary production. Thirdly, I determined the effect of short-term sediment transport events on the function of the microbial community and on the influence of the microbial community on vertical water exchange. The results show that the mechanical stress associated with short-term sediment transport events does not influence the microbial community function. However, a single short-term sediment transport event increased vertical water exchange by (i) releasing the gas bubbles produced by the microbial community and (ii) creating irregularities in the flume bed. Lastly, I ascertained the potential of benthic algal mats to transport sediment by means of buoyancy-mediated detachment from the bed. The results revealed the detachment of algal mats as a novel mechanism of sediment transport during low-flow periods. Overall, the interactions studied show that in sandy streambeds (i) the pattern of vertical water exchange is the primary physical template for the microbial community, and (ii) the activity of the microbial community and sediment transport are stochastic sources of spatiotemporal heterogeneity in vertical water exchange. These results contribute to the understanding and prediction of stream ecosystem functions in sandy streams, which is of special significance in light of the increase in fine sediment load in streams worldwide.}, subject = {Flumes; Hyporheic zone; Lowland streams; Colmation/Sedimentation; Rinnen; Hyporheische Interstitial; Flachland B{\"a}che; Sedimentation; Flachland; Bach; Sedimentation; Hyporheisches Interstitial}, language = {en} } @phdthesis{Schreckinger2023, author = {Schreckinger, Jos{\´e}}, title = {Short- and long-term succession in intermittent rivers and ephemeral streams : sediment microbial communities structure and biogeochemical trajectories}, doi = {10.26127/BTUOpen-6379}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-63793}, school = {BTU Cottbus - Senftenberg}, year = {2023}, abstract = {Intermittent rivers and ephemeral streams (IRES) experience drying events, and they are becoming increasingly common due to climate change and anthropogenic water withdrawal. Despite their prevalence, IRES have been less studied than non-drying rivers, and more research is needed to understand their dynamics. This dissertation examines drying events' effects on the sediment microbial community structure and biogeochemistry in temperate IRES. First, a research study was carried out using an outdoor mesocosm setup to track changes in bacterial and fungal communities, microbial functions and properties of sediment-dissolved organic carbon during three different drying events. Results showed that drying duration and intensity and sediment organic matter content regulated river Spree sediment microbial community composition and biogeochemical processes during drying. The associated sediment respiration, assessed as CO2 flux, rapidly declined during all drying treatments, and Bacilli class became the most dominant bacteria after 90 days of drying, except in non-enriched sediment under the most intense drying. Second, a microcosm experiment was conducted to understand how sediment drying history and properties influence biogeochemical dynamics during an IRES expansion phase. Sediment respiration and nutrient release/retention rates were measured through flow resumption, and results showed that drying duration and intensity and sediment organic matter content regulated the dynamics of nutrients and respiration upon flow resumption. Under the most intense and prolonged drying, non-enriched sediment showed a lag response in respiration during the first day after flow resumption, while all other treatments had either a linear increase or a fast pulse in respiration. Finally, the long-term microbial succession in IRES sediment and soil in the experimental catchment of Chicken Creek was investigated. In 2008 and 2018, the sediment of three ephemeral streams and their adjacent soil was analyzed for the structure of the bacterial and fungal communities and microbial functions across different seasons. Results showed that environmental factors, such as vegetation type and organic matter content, mediated sediment and soil microbial succession in Chicken Creek. Ephemeral streams under spare and sporadic flow events remained unique ecosystems with distinctive microbial communities and biogeochemical dynamics, different from its riparian soil. Overall, this dissertation concludes that temperate IRES are dynamic ecosystems where dry-wet cycles and environmental factors modulate their sediment microbial community structure and function trajectories in the short- and long term.}, subject = {Rivers; Drying; Biogeochemistry; Bacteria; Fungi; Fl{\"u}sse; Trocknung; Biogeochemie; Bakterien; Pilze; Fluss; Bach; Bakterien; Pilze; Biogeochemie; D{\"u}rre; Klimawandel; Flusssediment}, language = {en} } @inproceedings{Ramm2015, author = {Ramm, Jessica}, title = {Spatial variability and germination potential of cyanobacterial akinetes in sediments of deep dimictic lakes}, series = {PLANKTON RESTING STAGES 2015 WORKSHOP: Geological, Ecological and Evolutionary Perspectives, held in Hanko (Tv{\"a}rminne Zoological Station), Finnland, 5-8 October 2015}, booktitle = {PLANKTON RESTING STAGES 2015 WORKSHOP: Geological, Ecological and Evolutionary Perspectives, held in Hanko (Tv{\"a}rminne Zoological Station), Finnland, 5-8 October 2015}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-41552}, year = {2015}, abstract = {Nostocales form thick-walled, resting cells (akinetes) for overwintering in lake sediments of Central Europe. The pelagic Nostocales population recruits after the germination of akinetes, which mainly takes place in the spring with increasing temperatures and light intensities. The study aimed to i) characterize the sediment surfaces inhabited by viable akinetes that potentially contribute to the formation of a pelagic population, and ii) estimate the inoculum size of the available sedimentary akinete pool. We investigated the horizontal distribution of akinetes in sediments and the seasonal course of light and temperature in two deep dimictic lakes (Lake Stechlinsee, max. depth 69 m and Lake Scharm{\"u}tzelsee, max. depth 29.5 m; NE Germany). The akinete pool was calculated and the potential inoculum was estimated using assumed light and temperature data for akinete germination. The akinete abundance in sediments depended on the basin morphometry and increased with water depth. Only a small proportion of the viable akinete pool in shallow water areas contributed as inoculum to pelagic population. The potential inoculum size in Lake Scharm{\"u}tzelsee was larger than in Lake Stechlinsee.}, subject = {Cyanobacteria; Dimitic lakes; Akinetes; Sediments; Cyanobakterien; Limnobakteriologie; Seesediment}, language = {en} } @phdthesis{Bouchnak2011, author = {Bouchnak, Rihab}, title = {Steuerung der Energieallokation in Cladoceren durch Futteralgen unterschiedlicher Qualit{\"a}t und unter Stressbedingungen}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-22092}, school = {BTU Cottbus - Senftenberg}, year = {2011}, abstract = {Viele biotische und abiotische Faktoren, wie die Nahrungsqualit{\"a}t und diverse chemische Stressoren, bestimmen die Lebensparameter von Cladoceren. Diese Arbeit konzentriert sich auf die Effekte der unterschiedlichen Futteralgen (Pseudokirchneriella subcapitata, Monoraphidium minutum und Desmodesmus armatus) auf die Lebensparameter von vier Cladoceren-Arten (Daphnia magna, D. galeata, Moina macrocopa und M. micrura) in An- und Abwesenheit von chemischem Stress, ausgel{\"o}st durch den Huminstoff HuminFeed® (HF). Um die Effekte von HF auf D. magna zu ermitteln, wurden Lebenszyklusexperimente durchgef{\"u}hrt. In umweltrelevanten Konzentrationen wirkte HF lebensverl{\"a}ngernd, jedoch zeigten sich Verminderung in der Reproduktion. Die Ergebnisse wurden im Licht der Disposable Soma Theorie diskutiert. Es konnte keine Steuerung der Energieallokation durch HF und durch die Futteralgenqualit{\"a}t festgestellt werden. In einem Multigenerationsexperiment wurde der Einfluss von HF auf D. magna {\"u}ber drei Generationen hinweg betrachtet. Dabei bewirkte HF stets eine Verminderung der Reproduktion und eine Erh{\"o}hung der Lebensspanne. Die Ergebnisse des ersten Filialgenerationsversuchs F1 haben gezeigt, dass ein signifikanter Unterschied in der Fruchtbarkeit von Versuchstieren besteht, die in derselben Umwelt aufgewachsen sind (ohne HF), aber deren M{\"u}tter (P) unterschiedlichen Behandlungen ausgesetzt waren. Die Ergebnisse des zweiten Filialgenerationsversuchs F2 haben aber aufgezeigt, dass die Umwelt, in der die Parentalgeneration aufgewachsen ist, die Fruchtbarkeit der F2 Generation nicht nachhaltig beeinflusst. Es handelt sich vermutlich um Transgenerationseffekte (epigenetische Programmierung). In einem Langzeitexperiment wurden die Auswirkungen vom HF auf die Reproduktion und die Lebensspanne von D. galeata untersucht. Es zeigte sich, dass HF erneut eine Steigerung der Lebensdauer und eine Verringerung der Reproduktion bewirkt. Die Ergebnisse wurden im Licht der Disposable Soma Theorie diskutiert. Des Weiteren wurde der Einfluss von HF auf die Lebensparameter von M. macrocopa untersucht. Durch die Zugabe von HF bei F{\"u}tterung mit D. armatus wurde teilweise eine Verk{\"u}rzung der Lebensspanne und eine Erh{\"o}hung der Nachkommenzahl hervorgerufen. Bei F{\"u}tterung mit P. subcapitata zeigte sich, dass HF keine signifikanten Effekte erzielte. Bei F{\"u}tterung mit M. minutum konnte in exponierten Ans{\"a}tzen eine Verl{\"a}ngerung der Lebensspanne und Erh{\"o}hung der durchschnittlichen kumulativen Nachkommenzahl festgestellt werden. Hormon{\"a}hnliche Effekte der Huminstoffe wurden in Betracht gezogen. Die unterschiedliche Antwort von M. macrocopa auf Huminstoffe bei verschiedenen Futteralgen kann darauf hindeuten, dass die Energieallokation in M. macrocopa bei HF-Exposition durch die Futteralgenqualit{\"a}t gesteuert wird. Ebenfalls wurde bei M. micrura festgestellt, dass die Energieallokation unter dem chemischen Stressor HF durch die Futteralgenqualit{\"a}t gesteuert wurde. So wurde gezeigt, dass HF einen (teilweise signifikant) negativen Einfluss sowohl auf die Lebensspanne als auch auf die Fruchtbarkeit hat, wenn die Versuchstiere mit P. subcapitata gef{\"u}ttert wurden. Werden M. micrura hingegen mit M. minutum gef{\"u}ttert, wirkte HF teilweise lebensverk{\"u}rzend und ein Trend zur Erh{\"o}hung der Nachkommenzahl war sichtbar. Diese Arbeit gibt Hinweise darauf, dass zwischen den Zooplanktonarten Unterschiede hinsichtlich der Antwort auf chemischen Stress und des Bedarfs an einzelnen Futterqualit{\"a}tsfaktoren bestehen.}, subject = {Wasserfl{\"o}he; Algen; Futter; Lebensdauer; Futteralgen; Cladoceren; Huminstoffe; Stress; Algal food; Cladocera; Humic substance; Stress}, language = {de} } @techreport{Nixdorf2014, author = {Nixdorf, Brigitte}, title = {Stickstofflimitation in Binnengew{\"a}ssern - Ist Stickstoffreduktion {\"o}kologisch sinnvoll und wirtschaftlich vertretbar? Abschlussbericht NITROLIMIT I {\"u}berarbeitete Fassung}, organization = {Projekt NITROLIMIT c/o Brandenburgische Technische Universit{\"a}t Cottbus, Lehrstuhl Gew{\"a}sserschutz, Forschungsstelle Bad Saarow}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-41845}, year = {2014}, abstract = {In NITROLIMT stand an erster Stelle die Frage: Ist N-Reduktion {\"o}kologisch sinnvoll? Die Auswertung der Seendatenbank hat gezeigt, dass Stickstoff weit h{\"a}ufiger die Biomasse des Phytoplanktons begrenzt und damit die Gew{\"a}sserg{\"u}te bestimmt als bisher angenommen. In flachen durchmischten Seen und Flussseen tritt N-Limitation sogar h{\"a}ufiger auf als P-Limitation, wobei meist ein {\"U}bergang von P-Limitation im Fr{\"u}hjahr zu N-Limitation im Sommer stattfindet. Diese Befunde wurden durch Gew{\"a}ssermonitoring und Bioassays in vier Modellgew{\"a}ssern best{\"a}tigt. Demnach ist nicht nur P-, sondern auch N-Reduktion {\"o}kologisch sinnvoll. Daher wurden seentypspezifische Zielwerte f{\"u}r TN- und TP-Konzentrationen zur Erreichung eines guten {\"o}kologischen Zustandes ermittelt. „Ist-" und „Sollzustand" der so ermittelten TN- bzw. TP-Konzentrationen differieren stark. Der Zusammenhang zwischen TN und Biomasse des Phytoplanktons ist aufgrund der kleineren Datenmenge f{\"u}r TN, uneinheitlicher N-Analytik und unber{\"u}cksichtigter gel{\"o}ster organischer N-Verbindungen (DON) sehr variabel. Eine Validierung der TN-Zielwerte basierend auf einer verbesserten Datengrund-lage wird daher in NITROLIMIT II angestrebt. Zudem galt es zu beantworten: Ist Stickstoffreduktion wirtschaftlich vertretbar? Ein Maßnahmenkatalog zur N{\"a}hrstoffreduktion (N und P) f{\"u}r die Bereiche Landwirtschaft und urbane Quellen wurde erstellt. Darin sind Informationen zu Wirkungen und Kosten der einzelnen Maßnahmen zusammengestellt. Zudem wurden in einer {\"O}kobilanz nichtmonet{\"a}re {\"o}kologische Auswirkungen verschiedener Varianten einer N-Elimination auf Großkl{\"a}rwerken an einem Modellkl{\"a}rwerk untersucht. Hier zeigten sich signifikante Unterschiede in Wirksamkeit und Energieeffizienz zwischen den verschiedenen Maßnahmen, die bei der weiteren Maßnahmenplanung f{\"u}r Großkl{\"a}rwerke ber{\"u}cksichtigt werden sollten. F{\"u}r die {\"o}kobilanzielle Bewertung von Maßnahmen im urbanen Bereich fehlt noch die Untersuchung von Maßnahmen der Regenwasserbewirtschaftung. Vorl{\"a}ufiges Fazit Die bisherigen Ergebnisse zeigen, dass Stickstoffreduktion {\"u}berwiegend {\"o}kologisch sinnvoll und f{\"u}r einige der analysierten Szenarien wirtschaftlich vertretbar ist. Daher wird empfohlen, zur Verbesserung der Gew{\"a}sserg{\"u}te nicht nur den Eintrag von Phosphor, sondern auch den von Stickstoff zu reduzieren. Entsprechende regionale Konzepte zur N{\"a}hrstoffreduktion sollten f{\"u}r kleine Modelleinzugsgebiete erstellt und umgesetzt werden. Durch wissenschaftliche Begleituntersuchungen sollten dabei der Erfolg von einzelnen Maßnahmen und Maßnahmenkombinationen gepr{\"u}ft und Schl{\"u}sselprozesse des N- und P-Umsatzes (N2-Fixierung, Denitrifikation und P-Freisetzung) weiter aufgekl{\"a}rt werden.}, subject = {Stickstofflimitation; Stickstoffbelastung; Wasserg{\"u}te}, language = {de} } @phdthesis{Tingwey2009, author = {Tingwey, Emilienne Ingie}, title = {Studies on the life cycle of akinete forming cyanobacterium Cylindrospermopsis raciborskii in the temperate region}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-7766}, school = {BTU Cottbus - Senftenberg}, year = {2009}, abstract = {In recent years Cylindrospermopsis raciborskii (Woloszynska) Seenayya et Subba Raju a potentially toxic freshwater cyanobacterium of the order Nostocales initially classified as a tropical species, has invaded the temperate region and has established in lakes in northern Germany. The formation of dormant cells (akinetes) is an important part of the life cycle which enables Nostocales species to survive harsh conditions like the winter in the temperate zone. In this thesis, my aim is to throw more light on the life cycle of the invasive cyanobacterium Cylindrospermopsis raciborskii and also to compare it to native Nostocales species of the genus Aphanizomenon using derived field and laboratory data. This would help in the understanding of the invasion of C. raciborskii and spread and how it can be contained. Abiotic factors influencing the development and growth of photoautotrophic planktonic organisms in nature are examined and their variation with the years is discussed. A comprehensive look at C. raciborskii's akinetes in the sediment and the filaments and akinetes in the water column is done. The timing and temperature condition of akinete germination, recruitment, formation in the pelagic and importation into the sediment is determined. An assessment of the role of abiotic factors on the dynamics and abundance of filaments is done with a statistical model used to isolate which abiotic factors are most influential on the population growth of C. raciborskii. Akinetes distribution on the bed of the lake and the effect of loss processes on their abundance are looked into. Cylindrospermopsis is compared to native species Aphanizomenon spp in terms of the seasonal dynamics and the germination condition of their akinetes. The main findings in this thesis were that the seasonal dynamics of C. raciborskii had a similar trend but different timing of each event in the four years of the study. The variabilities were due to the different timing of the abiotic conditions. But in all temperature was identified as the most important factor influencing the timing of most events with germination of akinetes occurring at 13°C which is lower than so far reported in literature Subsequent increment in temperature to at least 23°C was found to be essential for the development of high populations of C. raciborskii in the water column. With a drop of temperature in autumn the filaments are stimulated in to producing akinetes which settle out into the sediment and remain there until the next spring when favourable conditions force them to germinate. They might also be consumed before germination by non identified grazer or losses due to microbial infections are discussed. Overall, the native Nostocales species of the genus Aphanizomenon have a selective advantage over the invaded species C. raciborskii under low temperatures and temperature fluctuations in spring as observed from the field and laboratory studies.}, subject = {Blaualgen; Extrembiotop; Mikrobiologie; Akinet; Laboruntersuchungen; S{\"u}ßwasser-Cyanobakterium; Lebenszyklus; Akinete; Laboratory experiments; Freshwater cyanobakterium; Life cycle}, language = {en} } @masterthesis{Krueger2015, type = {Bachelor Thesis}, author = {Kr{\"u}ger, Simone}, title = {The impact of discharge regulation on microbial sediment respiration at a land-water-interface of the river Spree}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-40496}, school = {BTU Cottbus - Senftenberg}, year = {2015}, abstract = {Flooding of dry sediments is known to trigger pulses of microbial respiration at land-water-interfaces. The regulation of discharge variability is therefore proposed to affect the respiration balance of these sites. In this study, I assessed the impact of discharge regulation on microbial respiration associated to surface sediments at a land-water-interface of the river Spree. I developed a theoretical model, based on empirical respiration data, to estimate the two-month total respiration at the study site for three discharge scenarios. The real scenario represented the actual discharge at the study site, which was regulated by the Spremberg reservoir dam. In the unregulated scenario, the regulating effect by the dam was excluded. In the extremely regulated scenario, a hypothetical constant discharge was modeled. For each scenario, the daily discharge, the corresponding flooded areas, the extent of dry or rewetted areas, and the durations of flooding or rewetting by rain at the study site were determined. Microbial respiration rates associated to surface sediments were measured with a respirometer under flooded, dry, and rewetted conditions. The model applied these rates to the respective flooded, dry or rewetted areas of the study site, to calculate the daily areal respiration. In all sediments from the land-water-interface, a distinctive respiration pulse was measured on the first day of flooding, and higher respiration rates under flooded than under dry conditions. The discharge of the unregulated scenario was characterized by a higher variability and larger flow volume than the regulated real scenario. Due to the higher total discharge, larger areas were flooded in the unregulated scenario, the total respiration from sediments under long-term flooded conditions was therefore higher. Moreover, the daily extent of flooded areas fluctuated more strongly, hence more short-term respiration pulses upon flooding were triggered than in the real regulated scenario. The calculated total two-month respiration of the unregulated scenario exceeded that of the regulated real scenario by almost 14 \%. These results suggest that discharge regulation can have a considerable negative impact on sediment-associated microbial respiration at land-water-interfaces.}, subject = {Respiration; Land-water-interface; Spree; Atmung; Bodenatmung; Flussufer}, language = {en} }