TY - GEN A1 - Nausch, Monika A1 - Bach, Lennart Thomas A1 - Czerny, Jan A1 - Goldstein, Josephine A1 - Grossart, Hans-Peter A1 - Hellemann, Dana A1 - Hornick, Thomas A1 - Achterberg, Eric Pieter A1 - Schulz, Kai Georg A1 - Riebesell, Ulf T1 - Effects of CO 2 perturbation on phosphorus pool sizes and uptake in a mesocosm experiment during a low productive summer season in the northern Baltic Sea T2 - Biogeosciences N2 - Studies investigating the effect of increasing CO2 levels on the phosphorus cycle in natural waters are lacking although phosphorus often controls phytoplankton development in many aquatic systems. The aim of our study was to analyse effects of elevated CO2 levels on phosphorus pool sizes and uptake. The phosphorus dynamic was followed in a CO2-manipulation mesocosm experiment in the Storfjarden (western Gulf of Finland, Baltic Sea) in summer 2012 and was also studied in the surrounding fjord water. In all mesocosms as well as in surface waters of Storfjarden, dissolved organic phosphorus (DOP) concentrations of 0.26aEuro-+/- aEuro-0.03 and 0.23aEuro-+/- aEuro-0.04aEuro-A mu molaEuro-L-1, respectively, formed the main fraction of the total P-pool (TP), whereas phosphate (PO4) constituted the lowest fraction with mean concentration of 0.15aEuro-A +/- aEuro-0.02 in the mesocosms and 0.17aEuro-A +/- aEuro-0.07aEuro-A mu molaEuro-L-1 in the fjord. Transformation of PO4 into DOP appeared to be the main pathway of PO4 turnover. About 82aEuro-% of PO4 was converted into DOP whereby only 18aEuro-% of PO4 was transformed into particulate phosphorus (PP). PO4 uptake rates measured in the mesocosms ranged between 0.6 and 3.9aEuro-nmolaEuro-L(-1)aEuro-h(-1). About 86aEuro-% of them was realized by the size fraction < aEuro-3aEuro-A mu m. Adenosine triphosphate (ATP) uptake revealed that additional P was supplied from organic compounds accounting for 25-27aEuro-% of P provided by PO4 only. CO2 additions did not cause significant changes in phosphorus (P) pool sizes, DOP composition, and uptake of PO4 and ATP when the whole study period was taken into account. However, significant short-term effects were observed for PO4 and PP pool sizes in CO2 treatments > aEuro-1000aEuro-A mu atm during periods when phytoplankton biomass increased. In addition, we found significant relationships (e.g., between PP and Chl a) in the untreated mesocosms which were not observed under high fCO(2) conditions. Consequently, it can be hypothesized that the relationship between PP formation and phytoplankton growth changed with CO2 elevation. It can be deduced from the results, that visible effects of CO2 on P pools are coupled to phytoplankton growth when the transformation of PO4 into POP was stimulated. The transformation of PO4 into DOP on the other hand does not seem to be affected. Additionally, there were some indications that cellular mechanisms of P regulation might be modified under CO2 elevation changing the relationship between cellular constituents. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 424 KW - Eastern Gotland basin KW - nodularia spumigena KW - organic-matter KW - filamentous cyanobacteria KW - Ocean acidification KW - nitrogen-fixation KW - PCO(2) levels KW - elevated CO2 KW - Peece-III KW - seawater Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-410274 ER - TY - GEN A1 - Spilling, Kristian A1 - Schulz, Kai Georg A1 - Paul, Allanah J. A1 - Boxhammer, Tim A1 - Achterberg, Eric Pieter A1 - Hornick, Thomas A1 - Lischka, Silke A1 - Stuhr, Annegret A1 - Bermúdez, Rafael A1 - Czerny, Jan A1 - Crawfurd, Kate A1 - Brussaard, Corina P. D. A1 - Grossart, Hans-Peter A1 - Riebesell, Ulf T1 - Effects of ocean acidification on pelagic carbon fluxes in a mesocosm experiment T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - About a quarter of anthropogenic CO2 emissions are currently taken up by the oceans, decreasing seawater pH. We performed a mesocosm experiment in the Baltic Sea in order to investigate the consequences of increasing CO2 levels on pelagic carbon fluxes. A gradient of different CO2 scenarios, ranging from ambient (similar to 370 mu atm) to high (similar to 1200 mu atm), were set up in mesocosm bags (similar to 55m(3)). We determined standing stocks and temporal changes of total particulate carbon (TPC), dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and particulate organic carbon (POC) of specific plankton groups. We also measured carbon flux via CO2 exchange with the atmosphere and sedimentation (export), and biological rate measurements of primary production, bacterial production, and total respiration. The experiment lasted for 44 days and was divided into three different phases (I: t0-t16; II: t17-t30; III: t31-t43). Pools of TPC, DOC, and DIC were approximately 420, 7200, and 25 200 mmol Cm-2 at the start of the experiment, and the initial CO2 additions increased the DIC pool by similar to 7% in the highest CO2 treatment. Overall, there was a decrease in TPC and increase of DOC over the course of the experiment. The decrease in TPC was lower, and increase in DOC higher, in treatments with added CO2. During phase I the estimated gross primary production (GPP) was similar to 100 mmol C m(-2) day(-1), from which 75-95% was respired, similar to 1% ended up in the TPC (including export), and 5-25% was added to the DOC pool. During phase II, the respiration loss increased to similar to 100% of GPP at the ambient CO2 concentration, whereas respiration was lower (85-95% of GPP) in the highest CO2 treatment. Bacterial production was similar to 30% lower, on average, at the highest CO2 concentration than in the controls during phases II and III. This resulted in a higher accumulation of DOC and lower reduction in the TPC pool in the elevated CO2 treatments at the end of phase II extending throughout phase III. The "extra" organic carbon at high CO2 remained fixed in an increasing biomass of small-sized plankton and in the DOC pool, and did not transfer into large, sinking aggregates. Our results revealed a clear effect of increasing CO2 on the carbon budget and mineralization, in particular under nutrient limited conditions. Lower carbon loss processes (respiration and bacterial remineralization) at elevated CO2 levels resulted in higher TPC and DOC pools than ambient CO2 concentration. These results highlight the importance of addressing not only net changes in carbon standing stocks but also carbon fluxes and budgets to better disentangle the effects of ocean acidification. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 544 KW - tecdissolved organic nitrogen KW - sea plankton community KW - high CO2 ocean KW - Baltic Sea KW - elevated CO2 KW - marine viruses KW - Atlantic-ocean KW - Natural-waters KW - Flow-cytometry KW - technical note Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-411835 SN - 1866-8372 IS - 544 ER - TY - JOUR A1 - Marce, Rafael A1 - George, Glen A1 - Buscarinu, Paola A1 - Deidda, Melania A1 - Dunalska, Julita A1 - de Eyto, Elvira A1 - Flaim, Giovanna A1 - Grossart, Hans-Peter A1 - Istvanovics, Vera A1 - Lenhardt, Mirjana A1 - Moreno-Ostos, Enrique A1 - Obrador, Biel A1 - Ostrovsky, Ilia A1 - Pierson, Donald C. A1 - Potuzak, Jan A1 - Poikane, Sandra A1 - Rinke, Karsten A1 - Rodriguez-Mozaz, Sara A1 - Staehr, Peter A. A1 - Sumberova, Katerina A1 - Waajen, Guido A1 - Weyhenmeyer, Gesa A. A1 - Weathers, Kathleen C. A1 - Zion, Mark A1 - Ibelings, Bas W. A1 - Jennings, Eleanor T1 - Automatic High Frequency Monitoring for Improved Lake and Reservoir Management JF - Frontiers in plant science N2 - Recent technological developments have increased the number of variables being monitored in lakes and reservoirs using automatic high frequency monitoring (AHFM). However, design of AHFM systems and posterior data handling and interpretation are currently being developed on a site-by-site and issue-by-issue basis with minimal standardization of protocols or knowledge sharing. As a result, many deployments become short-lived or underutilized, and many new scientific developments that are potentially useful for water management and environmental legislation remain underexplored. This Critical Review bridges scientific uses of AHFM with their applications by providing an overview of the current AHFM capabilities, together with examples of successful applications. We review the use of AHFM for maximizing the provision of ecosystem services supplied, by lakes and reservoirs (consumptive and non consumptive uses, food production, and recreation), and for reporting lake status in the EU Water Framework Directive. We also highlight critical issues to enhance the application of AHFM, and suggest the establishment of appropriate networks to facilitate knowledge sharing and technological transfer between potential users. Finally, we give advice on how modern sensor technology can successfully be applied on a larger scale to the management of lakes and reservoirs and maximize the ecosystem services they provide. Y1 - 2016 U6 - https://doi.org/10.1021/acs.est.6b01604 SN - 0013-936X SN - 1520-5851 VL - 50 SP - 10780 EP - 10794 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Srivastava, Abhishek A1 - McMahon, Katherine D. A1 - Stepanauskas, Ramunas A1 - Grossart, Hans-Peter T1 - De novo synthesis and functional analysis of the phosphatase-encoding gene acI-B of uncultured Actinobacteria from Lake Stechlin (NE Germany) JF - International microbiology : official journal of the Spanish Society for Microbiology N2 - The National Center for Biotechnology Information [http://www.ncbi.nlm.nih. gov/guide/taxonomy/] database enlists more than 15,500 bacterial species. But this also includes a plethora of uncultured bacterial representations. Owing to their metabolism, they directly influence biogeochemical cycles, which underscores the the important status of bacteria on our planet. To study the function of a gene from an uncultured bacterium, we have undertaken a de novo gene synthesis approach. Actinobacteria of the acI-B subcluster are important but yet uncultured members of the bacterioplankton in temperate lakes of the northern hemisphere such as oligotrophic Lake Stechlin (NE Germany). This lake is relatively poor in phosphate (P) and harbors on average similar to 1.3 x 10(6) bacterial cells/ml, whereby Actinobacteria of the ac-I lineage can contribute to almost half of the entire bacterial community depending on seasonal variability. Single cell genome analysis of Actinobacterium SCGC AB141-P03, a member of the acI-B tribe in Lake Stechlin has revealed several phosphate-metabolizing genes. The genome of acI-B Actinobacteria indicates potential to degrade polyphosphate compound. To test for this genetic potential, we targeted the exoP-annotated gene potentially encoding polyphosphatase and synthesized it artificially to examine its biochemical role. Heterologous overexpression of the gene in Escherichia coli and protein purification revealed phosphatase activity. Comparative genome analysis suggested that homologs of this gene should be also present in other Actinobacteria of the acI lineages. This strategic retention of specialized genes in their genome provides a metabolic advantage over other members of the aquatic food web in a P-limited ecosystem. KW - acI-B in Actinobacteria KW - phosphatases KW - single cell genomics KW - phosphate limitation KW - Lake Stechlin KW - NE Germany Y1 - 2016 U6 - https://doi.org/10.2436/20.1501.01.262 SN - 1139-6709 SN - 1618-1905 VL - 19 SP - 39 EP - 47 PB - Institut d'Estudis Catalans CY - Barcelona ER - TY - JOUR A1 - Reverey, Florian A1 - Grossart, Hans-Peter A1 - Premke, Katrin A1 - Lischeid, Gunnar T1 - Carbon and nutrient cycling in kettle hole sediments depending on hydrological dynamics: a review JF - Hydrobiologia : acta hydrobiologica, hydrographica, limnologica et protistologica N2 - Kettle holes as a specific group of isolated, small lentic freshwater systems (LFS) often are (i) hot spots of biogeochemical cycling and (ii) exposed to frequent sediment desiccation and rewetting. Their ecological functioning is greatly determined by immanent carbon and nutrient transformations. The objective of this review is to elucidate effects of a changing hydrological regime (i.e., dry-wet cycles) on carbon and nutrient cycling in kettle hole sediments. Generally, dry-wet cycles have the potential to increase C and N losses as well as P availability. However, their duration and frequency are important controlling factors regarding direction and intensity of biogeochemical and microbiological responses. To evaluate drought impacts on sediment carbon and nutrient cycling in detail requires the context of the LFS hydrological history. For example, frequent drought events induce physiological adaptation of exposed microbial communities and thus flatten metabolic responses, whereas rare events provoke unbalanced, strong microbial responses. Different potential of microbial resilience to drought stress can irretrievably change microbial communities and functional guilds, gearing cascades of functional responses. Hence, dry-wet events can shift the biogeochemical cycling of organic matter and nutrients to a new equilibrium, thus affecting the dynamic balance between carbon burial and mineralization in kettle holes. KW - Drought KW - Rewetting KW - Temporary pond KW - Kettle hole KW - Organic matter KW - Nitrogen KW - Phosphorus Y1 - 2016 U6 - https://doi.org/10.1007/s10750-016-2715-9 SN - 0018-8158 SN - 1573-5117 VL - 775 SP - 1 EP - 20 PB - Springer CY - Dordrecht ER - TY - THES A1 - Fiedler, Dorothea T1 - Impact of Dissolved Organic Nitrogen on Freshwater Phytoplankton N2 - In freshwater sciences, nitrogen gained increasing attention in the past as an important resource potentially influencing phytoplankton growth and thus eutrophication. Most studies and all management approaches, however, are still restricted to dissolved inorganic nitrogen (DIN = nitrate + nitrite + ammonium) since dissolved organic nitrogen (DON) was considered to be refractory for most of the photoautotrophs. In the meantime this assumption has been disproved for all aquatic systems. While research on DON in marine ecosystems substantially increased, in freshwater a surprisingly small number of investigations has been carried out on DON utilization by phytoplankton or even the occurrence and seasonal development of total DON or its compounds in lakes. Therefore, our present knowledge on DON utilization by phytoplankton is often based on single species experiments using a sole, usually low molecular weight DON component, often in unnaturally high amounts mainly carried out with marine phytoplankton species. Thus, we know that some phytoplankton species can take up different DON fractions if they are available in high concentrations and as sole nitrogen source. This does not necessarily imply that phytoplankton would perform likewise in natural environments. In addition, it will be difficult to draw conclusions on the behavior of freshwater phytoplankton from experiments with marine phytoplankton since the nutrient regime in marine environments differs from that of freshwater. In the light of the parallel availability of inorganic and organic nitrogen species in natural freshwater ecosystems, several questions must be raised: "If inorganic nitrogen is available, would phytoplankton really rely on an organic nitrogen source? Could a connection be detected between the seasonal development of DON and changes in the phytoplankton community composition as found for inorganic nitrogen? And if we reduce the input of inorganic nitrogen in lakes and rivers would the importance of DON as nitrogen source for phytoplankton increase, counteracting all management efforts or even leading to undesired effects due to changes in phytoplankton physiology and biodiversity?" I experimentally addressed the questions whether those DON compounds differentially influence growth, physiology and composition of phytoplankton both as sole available nitrogen source and in combination with other nitrogen compounds. I hypothesized that all offered DON - compounds (urea, natural organic matter (NOM), dissolved free and combined amino acids (DFAA, DCAA)) could be utilized by phytoplankton at natural concentrations. However, I assumed that the availability would decrease with increasing compound complexity. I furthermore hypothesized that the occurrence of low DIN concentrations would not affect the utilization of DON negatively. The nitrogen source, whatsoever, would have an impact on phytoplankton physiology as well as community composition. To investigate these questions and assumptions I conducted bioassays with algae monocultures as well as phytoplankton communities testing the utilization of various DON compounds by several freshwater phytoplankton species. Especially the potential utilization of NOM, a complex DON compound mainly consisting of humic substances is of interest, since it is usually regarded to be refractory. In order to be able to use natural concentrations of DON - compounds for my experiments the concentration of total DON and some DON - compounds (urea, humic substances, heigh molecular weight substances) was assessed in Lake Müggelsee. All compounds were able to support algae growth in the low natural concentrations supplied. However, I found that the offered DON compounds differ in their availability to various algae species, both, as sole nitrogen source or in combination with low DIN concentrations. As expected, the availability decreased with increasing complexity of the nitrogen compound. Furthermore, I could show that changes in algal physiology (nitrogen storage, metabolism) occur depending on the utilized nitrogen source. Especially the secondary photosynthetic pigment composition, heterocyst frequency and C:N - ratio of the algae were affected. The uptake and usage of certain nitrogen compounds might be more costly, potentially resulting in those physiology changes. Whereas laboratory experiments with single species revealed strong effects of DON, algal responses to DON in a multi-species situation remain unclear. Experiments with phytoplankton communities from Lake Müggelsee revealed that the nitrogen pool composition does influence the phytoplankton community structure. The findings furthermore show that several species combined might utilize the supplied nitrogen completely different than monocultures in the laboratory. Thus, besides the actual ability of algae to use the offered nitrogen sources other factors, such as interspecific competition, may be of importance. I further investigated, if the results of the laboratory experiments, can be verified in the field. Here, I surveyed the seasonal development of several dissolved organic matter (DOM) components (urea, high molecular weight substances (HMWS), humic substances (HS)) and associated parameters (Specific UV-absorption (SUVA), C:N - ratio) in Lake Müggelsee between 2011 and 2013. Furthermore, data from the long term measurements series of Lake Müggelsee such as physical (temperature, light, pH, O2) and chemical parameters (nitrogen, phosphorous, silica, inorganic carbon), zooplankton and phytoplankton data were used to investigate how much of the variability of the phytoplankton composition in Lake Müggelsee can be explained by DON/DOM concentration and composition, relative to the other groups of explanatory variables. The results show that DON mainly consists of rather complex compounds such as humic substances and biopolymers (80 %) and that only slight seasonal trends are detectable. Using variance partitioning I could show, that the usually investigated nutrients (DIN, silica, inorganic carbon, phosphorous) and abiotic factors together explain most of the algae composition as was to be expected (57.1 % of modeled variance). However, DOM and the associated parameters uniquely explain 10.3 % of the variance and thus slightly more than zooplankton with 9.3 %. I could therefore prove, that the composition of DOM (nitrogen and carbon) is connected to the algae composition in an eutrophic lake such as Lake Müggelsee. DON - compounds such as urea, however, could not be correlated with the occurrence of specific phytoplankton species. Overall, the results of this study imply that DON can be a valuable nitrogen source for freshwater phytoplankton. DON is used by various species even when DIN is available in low concentrations. Through the reduction of DIN in lakes and rivers, the DON:DIN ratio might be changed, resulting even in an increased importance of DON as phytoplankton nitrogen source. My work suggests that not only N2-fixation but also DON utilization might compensate for reduced N - input. Changes from DIN to DON as main nitrogen source might also promote certain, potentially undesired algae species and influence the biodiversity of a limnic ecosystem through changes in the phytoplankton community structure. Thus, DON, especially urea, should be included in calculations concerning total available nitrogen and when determining nitrogen threshold values. Furthermore, the input-reduction of DON, for example from waste-water treatment plants should also be evaluated and the results of my thesis should find consideration when planning to reduce the nitrogen input in freshwater. N2 - Das Interesse an Stickstoff als potentielle Einflußgröße auf das Phytoplanktonwachstum und damit auch als Eutrophierungsfaktor hat in der Vergangenheit in der Limnologie stark zugenommen. Bisher ging man davon aus, das gelöster organischer Stickstoff (DON) für photoautotrophe Organismen refraktär, also nicht nutzbar ist. Dies führte dazu, dass der Großteil an Studien und Managementmaÿnahmen nur gelösten inorganischen Stickstoff (DIN = Nitrat + Nitrit + Ammonium) einbezieht. Mittlerweile wurde allerdings für alle aquatischen Systeme nachgewiesen, dass DON durchaus für Organismen verfügbar sein kann. Während die Forschung im marinen Bereich stark zugenommen hat, wurden in Binnengewässern nur sehr wenige Untersuchungen zur DON - Nutzung durch Phytoplankton oder auch nur das Vorkommen und die saisonale Entwicklung von DON oder seiner Komponenten durchgeführt. Dies resultiert darin, dass sich unser heutiges Wissen zur DON - Nutzung durch Pytoplankton hauptsächlich auf Experimente stützt, die mit einzelnen, überwiegend marinen Phytoplanktonarten und einer, üblicherweise niedermolekularen DON - Komponente in meist unnatürlich hohen Konzentrationen durchgeführt wurden. Demzufolge wissen wir nur, dass es einige Phytoplanktonarten gibt, die verschiedene DON - Fraktionen aufnehmen können, wenn sie in hohen Konzentrationen und als alleinige Stickstoffquelle vorliegen. Diese Ergebnisse spiegeln nicht das tatsächliche Verhalten von Phytoplankton in seiner natürlichen Umgebung wieder. Zudem ist es schwierig, von Experimenten mit marinen Phytoplanktonarten auf das Verhalten limnischer Phytoplankter zu schließen, da sich der Nährstoffhaushalt in marinen Systemen von dem in Binnengewässern stark unterscheidet. Im Hinblick auf die parallele Verfügbarkeit von inorganischem und organischem Stickstoff in natürlichen Binnengewässern stellen sich eine Vielzahl von Fragen: "Wie stark DON als Stickstoffquelle durch Phytoplankton genutzt wird, wenn auch inorganischer Stickstoff zur Verfügung steht. Gibt es eventuell eine Verbindung zwischen der saisonalen Entwicklung von DON und Änderungen in der Zusammensetzung der Phytoplanktongemeinschaft wie man es auch für inorganischen Stickstoff sowie andere biotische und abiotische Faktoren findet? Es ist bisher auch ungeklärt, ob durch eine Reduktion des Eintrags von inorganischem Stickstoff die Bedeutung von DON als Stickstoffquelle für Phytoplankton zunimmt. Würde so eventuell den Managmentmaßnahmen entgegengewirkt oder käme es zu ungewünschten Effekten durch Änderungen in Phytoplanktonphysiologie und Biodiversität?" Im Verlauf meiner Doktorarbeit habe ich mich mit einem Teil dieser offenen Fragen auseinandergesetzt. Meine Experimente dienten dazu herauszufinden, inwieweit sich verschiedene DON -Komponenten auf Wachstum, Physiologie und die Phytoplanktonzusammensetzung auswirken, wenn sie als einzige verfügbare Stickstoffquelle aber auch in Kombination mit anderen Stickstoffkomponenten zur Verfügung stehen. Hierbei stehen folgende Hypothesen und Annahmen im Vordergrund: a) alle angebotenen DON - Komponenten (Harnstoff, gelöste freie Aminosäuren (DFAA), gelöste gebundene Aminosäuren (DCAA) und natürliches organisches Material (NOM)) können in natürlicher Konzentration von Phytoplankton genutzt werden, b) die Verfügbarkeit nimmt mit zunehmender Komplexität des DON ab, c) geringe DIN - Konzentrationen haben keinen negativen Einfluss auf die Nutzung von DON durch das Phytoplankton, d) die Stickstoffquelle beeinflusst Phytoplanktonphysiologie sowie die Zusammensetzung der Phytoplanktongemeinschaft. Um mehr Informationen zur DON - Verfügbarkeit für Süßwasserphytoplankton zu erhalten, wurde zunächst die Nutzung verschiedener DON - Komponenten durch verschiedene Phytoplanktonspezies aus Binnengewässern sowie Phytoplanktongemeinschaften untersucht. Besonders die mögliche Nutzung von NOM, einer komplexen, hauptsächlich aus Huminstoffen bestehenden DON - Komponente war von Interesse, da sie überwiegend als refraktär eingeschätzt wird. Um die Verfügbarkeit diverser DON - Komponenten in natürlicher Konzentration zu testen, wurde zunächst die Konzentration von Gesamt - DON sowie einiger DON -Komponenten (Harnstoff, Huminstoffe, hochmolekulare Substanzen) im Müggelsee ermittelt. Alle DON - Komponenten ermöglichten ein Algenwachstum in der niedrigen natürlichen Konzentration, in der sie zur Verfügung gestellt wurden. Es konnte festgestellt werden, dass sich die unterschiedlichen DON - Komponenten in ihrer Verfügbarkeit für verschiedene Algenarten unterschieden, unabhängig davon, ob sie als alleinige Stickstoffquelle vorlagen oder in Kombination mit DIN in niedriger Konzentration. Wie erwartet nahm die Algenverfügbarkeit mit zunehmender Komplexität der Stickstoffkomponenten ab. Desweiteren konnte gezeigt werden, dass die verwendete Stickstoffquelle zu Änderungen in der Algenphysiologie (Metabolismus, Stickstoffspeicherung) führen kann. Vor allem die Zusammensetzung sekundärer Photosynthesepigmente, die Heterocystenhäufigkeit sowie das C:N - Verhältnis des Phytoplankton wurden beeinflusst. Auch wenn alle untersuchten Stickstoffquellen das Phytoplanktonwachstum ermöglichen, ist die Nutzung einiger Komponenten gegebenenfalls mit höheren Kosten z.B. für Transport, Aufschluß etc. verbunden, was wiederum in einer Änderungen der Phytoplanktonphysiologie resultieren kann. Während Experimente mit einzelnen Phytoplanktonarten im Labor starke Effekte von DON erkennen lassen, sind die Ergebnisse der Multi-Spezies-Versuche weniger eindeutig interpretierbar. Versuche mit Phytoplanktongemeinschaften aus dem Müggelsee zeigten, dass die Zusammensetzung des Stickstoffpools Auswirkungen auf die Struktur der Phytoplanktongemenschaft hat. Zudem nutzen verschiedene Arten zusammen den zur Verfügung gestellten Stickstoff anders, als Monokulturen im Labor. Demzufolge spielen neben der eigentlichen Fähigkeit der Algen, verschiedene Stickstoffkomponenten nutzen zu können noch andere Faktoren wie z.B. interspezifische Konkurrenz eine Rolle für die tatsächliche Nutzung im Gewässer. Im weiteren Teil meiner Doktorarbeit habe ich untersucht, inwieweit die Ergebnisse der Laborversuche im Feld verifiziert werden können. Dafür wurde die saisonale Entwicklung verschiedenen gelösten organischen Materials (DOM) (Harnstoff, hochmolekulare Substanzen (HMWS), Huminstoffe (HS)) und weitere assoziierte Parameter (spezifische UV-Absorption (SUVA), C:N - Verhältnis) im Müggelsee von 2011-2013 bestimmt. Desweiteren wurden Daten aus der Langzeitmessung vom Müggelsee verwendet, um herauszufinden, wieviel der Variabilität in der Phytoplanktonzusammensetzung im Müggelsee durch die DON / DOM Konzentration und Zusammensetzung erklärt werden, im Verhältnis zu den anderen potentiellen Einflussfaktoren. Hierzu zählen physikalische (Temperatur, Licht, pH, O2) und chemische Parameter (Stickstoff, Phosphor, Silikat, inorganischer Kohlenstoff), Zooplankton- und Phytoplanktondaten. Die Ergebnisse zeigen, dass sich DON hauptächlich aus komplexen Komponenten wie Huminstoffen und Biopolymeren (80 %) zusammensetzt und das nur ein geringer saisonaler Trend in der DON-Entwicklung festzustellen ist. Mittels Varianzpartitionierung konnte gezeigt werden, dass die üblicherweise untersuchten Nährstoffe (DIN, Silikat, inorganischer Kohlenstoff, Phosphor) und abiotische Faktoren zusammen den Großteil der Algenzusammensetzung erklären, wie zu erwarten war (57.1 %). DOM und die damit assoziierten Parameter konnten allein 10.3% der Varianz erklären und damit etwas mehr als Zooplankton, eine anerkannte Einflußgröße, mit 9.3%. Damit konnte gezeigt werden, dass auch die DOM - Zusammensetzung (Stickstoff und Kohlenstoff) als Einflussgröße der Algenzusammensetzung in einem eutrophen See wie dem Müggelsee berücksichtigt werden sollte. Zusammenfassend zeigen die Ergebnisse dieser Doktorarbeit, dass DON eine wichtige Stickstoffquelle für Phytoplankton aus Binnengewässern sein kann und von zahlreichen Arten genutzt wird, auch wenn DIN, zumindest in niedrigen Konzentrationen, verfügbar ist. Durch die Reduktion von DIN in Seen und Flüssen könnte es zu einer Änderung des DON / DIN - Verhältnisses kommen, was zu einer noch stärkeren Bedeutung von DON als Stickstoffquelle für Phytoplankton führen kann. Meine Arbeit legt nahe, dass nicht nur die N2 - Fixierung, sondern auch die Nutzung von DON eine Reduktion des Stickstoffeintrags kompensieren könnte. Ein Wechsel von DIN zu DON als Hauptstickstoffquelle für Phytoplankton fördert möglicherweise auch bestimmte unerwünschte Algenarten und beeinflusst die Biodiversität der Binnengewässer durch Änderungen in der Phytoplanktongemeinschaft. Aus diesen Gründen sollte DON, vor allem Harnstoff in Kalkulationen des gesamtverfögbaren Stickstoffs sowie bei der Ermittlung von Stickstoffgrenzwerten einbezogen werden. Bei der Planung von Maßnahmen zur Reduktion des Stickstoffeintrages in Binnengewässer zur Verbesserung der Wasserqualtät sollten die Ergebnisse dieser Doktorarbeit demzufolge in Betracht gezogen und auch eine Reduktion des DON - Eintrages, z. B. aus Klärwerken, erwogen werden. KW - DON KW - phytoplankton KW - natural organic matter KW - LC-OCD-OND Y1 - 2016 ER - TY - JOUR A1 - Spilling, Kristian A1 - Schulz, Kai G. A1 - Paul, Allanah J. A1 - Boxhammer, Tim A1 - Achterberg, Eric Pieter A1 - Hornick, Thomas A1 - Lischka, Silke A1 - Stuhr, Annegret A1 - Bermudez, Rafael A1 - Czerny, Jan A1 - Crawfurd, Kate A1 - Brussaard, Corina P. D. A1 - Grossart, Hans-Peter A1 - Riebesell, Ulf T1 - Effects of ocean acidification on pelagic carbon fluxes in a mesocosm experiment JF - Biogeosciences N2 - About a quarter of anthropogenic CO2 emissions are currently taken up by the oceans, decreasing seawater pH. We performed a mesocosm experiment in the Baltic Sea in order to investigate the consequences of increasing CO2 levels on pelagic carbon fluxes. A gradient of different CO2 scenarios, ranging from ambient (similar to 370 mu atm) to high (similar to 1200 mu atm), were set up in mesocosm bags (similar to 55m(3)). We determined standing stocks and temporal changes of total particulate carbon (TPC), dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and particulate organic carbon (POC) of specific plankton groups. We also measured carbon flux via CO2 exchange with the atmosphere and sedimentation (export), and biological rate measurements of primary production, bacterial production, and total respiration. The experiment lasted for 44 days and was divided into three different phases (I: t0-t16; II: t17-t30; III: t31-t43). Pools of TPC, DOC, and DIC were approximately 420, 7200, and 25 200 mmol Cm-2 at the start of the experiment, and the initial CO2 additions increased the DIC pool by similar to 7% in the highest CO2 treatment. Overall, there was a decrease in TPC and increase of DOC over the course of the experiment. The decrease in TPC was lower, and increase in DOC higher, in treatments with added CO2. During phase I the estimated gross primary production (GPP) was similar to 100 mmol C m(-2) day(-1), from which 75-95% was respired, similar to 1% ended up in the TPC (including export), and 5-25% was added to the DOC pool. During phase II, the respiration loss increased to similar to 100% of GPP at the ambient CO2 concentration, whereas respiration was lower (85-95% of GPP) in the highest CO2 treatment. Bacterial production was similar to 30% lower, on average, at the highest CO2 concentration than in the controls during phases II and III. This resulted in a higher accumulation of DOC and lower reduction in the TPC pool in the elevated CO2 treatments at the end of phase II extending throughout phase III. The "extra" organic carbon at high CO2 remained fixed in an increasing biomass of small-sized plankton and in the DOC pool, and did not transfer into large, sinking aggregates. Our results revealed a clear effect of increasing CO2 on the carbon budget and mineralization, in particular under nutrient limited conditions. Lower carbon loss processes (respiration and bacterial remineralization) at elevated CO2 levels resulted in higher TPC and DOC pools than ambient CO2 concentration. These results highlight the importance of addressing not only net changes in carbon standing stocks but also carbon fluxes and budgets to better disentangle the effects of ocean acidification. Y1 - 2016 U6 - https://doi.org/10.5194/bg-13-6081-2016 SN - 1726-4170 SN - 1726-4189 VL - 13 SP - 6081 EP - 6093 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Premke, Katrin A1 - Attermeyer, Katrin A1 - Augustin, Jürgen A1 - Cabezas, Alvaro A1 - Casper, Peter A1 - Deumlich, Detlef A1 - Gelbrecht, Jörg A1 - Gerke, Horst H. A1 - Gessler, Arthur A1 - Grossart, Hans-Peter A1 - Hilt, Sabine A1 - Hupfer, Michael A1 - Kalettka, Thomas A1 - Kayler, Zachary A1 - Lischeid, Gunnar A1 - Sommer, Michael A1 - Zak, Dominik T1 - The importance of landscape diversity for carbon fluxes at the landscape level: small-scale heterogeneity matters JF - Wiley Interdisciplinary Reviews : Water N2 - Landscapes can be viewed as spatially heterogeneous areas encompassing terrestrial and aquatic domains. To date, most landscape carbon (C) fluxes have been estimated by accounting for terrestrial ecosystems, while aquatic ecosystems have been largely neglected. However, a robust assessment of C fluxes on the landscape scale requires the estimation of fluxes within and between both landscape components. Here, we compiled data from the literature on C fluxes across the air–water interface from various landscape components. We simulated C emissions and uptake for five different scenarios which represent a gradient of increasing spatial heterogeneity within a temperate young moraine landscape: (I) a homogeneous landscape with only cropland and large lakes; (II) separation of the terrestrial domain into cropland and forest; (III) further separation into cropland, forest, and grassland; (IV) additional division of the aquatic area into large lakes and peatlands; and (V) further separation of the aquatic area into large lakes, peatlands, running waters, and small water bodies These simulations suggest that C fluxes at the landscape scale might depend on spatial heterogeneity and landscape diversity, among other factors. When we consider spatial heterogeneity and diversity alone, small inland waters appear to play a pivotal and previously underestimated role in landscape greenhouse gas emissions that may be regarded as C hot spots. Approaches focusing on the landscape scale will also enable improved projections of ecosystems’ responses to perturbations, e.g., due to global change and anthropogenic activities, and evaluations of the specific role individual landscape components play in regional C fluxes. WIREs Water 2016, 3:601–617. doi: 10.1002/wat2.1147 Y1 - 2016 U6 - https://doi.org/10.1002/wat2.1147 SN - 2049-1948 SN - 2049-1948 VL - 3 SP - 601 EP - 617 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Adel, Mustafa A1 - Elbehery, Ali H. A. A1 - Aziz, Sherry K. A1 - Aziz, Ramy K. A1 - Grossart, Hans-Peter A1 - Siam, Rania T1 - Viruses-to-mobile genetic elements skew in the deep Atlantis II brine pool sediments JF - Scientific reports N2 - The central rift of the Red Sea has 25 brine pools with different physical and geochemical characteristics. Atlantis II (ATIID), Discovery Deeps (DD) and Chain Deep (CD) are characterized by high salinity, temperature and metal content. Several studies reported microbial communities in these brine pools, but few studies addressed the brine pool sediments. Therefore, sediment cores were collected from ATIID, DD, CD brine pools and an adjacent brine-influenced site. Sixteen different lithologic sediment sections were subjected to shotgun DNA pyrosequencing to generate 1.47 billion base pairs (1.47 x 10(9) bp). We generated sediment-specific reads and attempted to annotate all reads. We report the phylogenetic and biochemical uniqueness of the deepest ATIID sulfur-rich brine pool sediments. In contrary to all other sediment sections, bacteria dominate the deepest ATIID sulfur-rich brine pool sediments. This decrease in virus-to-bacteria ratio in selected sections and depth coincided with an overrepresentation of mobile genetic elements. Skewing in the composition of viruses-to-mobile genetic elements may uniquely contribute to the distinct microbial consortium in sediments in proximity to hydrothermally active vents of the Red Sea and possibly in their surroundings, through differential horizontal gene transfer. Y1 - 2016 U6 - https://doi.org/10.1038/srep32704 SN - 2045-2322 VL - 6 SP - 8882 EP - 8888 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Cepakova, Zuzana A1 - Hrouzek, Pavel A1 - Ziskova, Eva A1 - Nuyanzina-Boldareva, Ekaterina A1 - Sorf, Michal A1 - Kozlikova-Zapomelova, Eliska A1 - Salka, Ivette A1 - Grossart, Hans-Peter A1 - Koblizek, Michal T1 - High turnover rates of aerobic anoxygenic phototrophs in European freshwater lakes JF - Environmental microbiology N2 - Aerobic Anoxygenic Phototrophic (AAP) bacteria are bacteriochlorophyll (BChl) a -containing organisms which use light energy to supplement their predominantly heterotrophic metabolism. Here, we investigated mortality and growth rates of AAP bacteria in three different freshwater lakes in Central Europe: the mountain lake Plesne, the oligo-mesotrophic Lake Stechlin and the forest pond Huntov. The mortality of AAP bacteria was estimated from diel changes of BChl a fluorescence. Net and gross growth rates were calculated from the increases in AAP cell numbers. The gross growth rates of AAP bacteria ranged from 0.38 to 5.6 d(-1), with the highest values observed during summer months. Simultaneously, the rapidly growing AAP cells have to cope with an intense grazing pressure by both zooplankton and protists. The presented results document that during the day, gross growth usually surpased mortality. Our results indicate that AAP bacteria utilize light energy under natural conditions to maintain rapid growth rates, which are balanced by a generally intense grazing pressure. Y1 - 2016 U6 - https://doi.org/10.1111/1462-2920.13475 SN - 1462-2912 SN - 1462-2920 VL - 18 SP - 5063 EP - 5071 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Tang, Kam W. A1 - McGinnis, Daniel F. A1 - Ionescu, Danny A1 - Grossart, Hans-Peter T1 - Methane Production in Oxic Lake Waters Potentially Increases Aquatic Methane Flux to Air JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - Active methane production in oxygenated lake waters challenges the long-standing paradigm that microbial methane production occurs only under anoxic conditions and forces us to rethink the ecology and environmental dynamics of this powerful greenhouse gas. Methane production in the upper oxic water layers places the methane source closer to the air water interface, where convective mixing and microbubble detrainment can lead to a methane efflux higher than that previously assumed. Microorganisms may produce methane in oxic environments by being equipped with enzymes to counteract the effects of molecular oxygen during methanogenesis or using alternative pathways that do not involve oxygen-sensitive enzymes. As this process appears to be influenced by thermal stratification, water transparency, and primary production, changes in lake ecology due to climate change will alter methane formation in oxic water layers, with far-reaching consequences for methane flux and climate feedback. Y1 - 2016 U6 - https://doi.org/10.1021/acs.estlett.6b00150 SN - 2328-8930 VL - 3 SP - 227 EP - 233 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Brentrup, Jennifer A. A1 - Williamson, Craig E. A1 - Colom-Montero, William A1 - Eckert, Werner A1 - de Eyto, Elvira A1 - Grossart, Hans-Peter A1 - Huot, Yannick A1 - Isles, Peter D. F. A1 - Knoll, Lesley B. A1 - Leach, Taylor H. A1 - McBride, Chris G. A1 - Pierson, Don A1 - Pomati, Francesco A1 - Read, Jordan S. A1 - Rose, Kevin C. A1 - Samal, Nihar R. A1 - Staehr, Peter A. A1 - Winslow, Luke A. T1 - The potential of high-frequency profiling to assess vertical and seasonal patterns of phytoplankton dynamics in lakes: an extension of the Plankton Ecology Group (PEG) model JF - Inland waters : journal of the International Society of Limnology N2 - The use of high-frequency sensors on profiling buoys to investigate physical, chemical, and biological processes in lakes is increasing rapidly. Profiling buoys with automated winches and sensors that collect high-frequency chlorophyll fluorescence (ChlF) profiles in 11 lakes in the Global Lake Ecological Observatory Network (GLEON) allowed the study of the vertical and temporal distribution of ChlF, including the formation of subsurface chlorophyll maxima (SSCM). The effectiveness of 3 methods for sampling phytoplankton distributions in lakes, including (1) manual profiles, (2) single-depth buoys, and (3) profiling buoys were assessed. High-frequency ChlF surface data and profiles were compared to predictions from the Plankton Ecology Group (PEG) model. The depth-integrated ChlF dynamics measured by the profiling buoy data revealed a greater complexity that neither conventional sampling nor the generalized PEG model captured. Conventional sampling techniques would have missed SSCM in 7 of 11 study lakes. Although surface-only ChlF data underestimated average water column ChlF, at times by nearly 2-fold in 4 of the lakes, overall there was a remarkable similarity between surface and mean water column data. Contrary to the PEG model’s proposed negligible role for physical control of phytoplankton during the growing season, thermal structure and light availability were closely associated with ChlF seasonal depth distribution. Thus, an extension of the PEG model is proposed, with a new conceptual framework that explicitly includes physical metrics to better predict SSCM formation in lakes and highlight when profiling buoys are especially informative. KW - chlorophyll fluorescence KW - Global Lake Ecological Observatory Network (GLEON) KW - high-frequency sensors KW - PEG model KW - phytoplankton KW - profiling buoys KW - subsurface chlorophyll maximum Y1 - 2016 U6 - https://doi.org/10.5268/IW-6.4.890 SN - 2044-2041 SN - 2044-205X VL - 6 SP - 565 EP - 580 PB - Freshwater Biological Association CY - Ambleside ER - TY - JOUR A1 - Cuadrat, Rafael R. C. A1 - Ferrera, Isabel A1 - Grossart, Hans-Peter A1 - Davila, Alberto M. R. T1 - Picoplankton Bloom in Global South? A High Fraction of Aerobic Anoxygenic Phototrophic Bacteria in Metagenomes from a Coastal Bay (Arraial do Cabo-Brazil) JF - OMICS : a journal of integrative biology N2 - Marine habitats harbor a great diversity of microorganism from the three domains of life, only a small fraction of which can be cultivated. Metagenomic approaches are increasingly popular for addressing microbial diversity without culture, serving as sensitive and relatively unbiased methods for identifying and cataloging the diversity of nucleic acid sequences derived from organisms in environmental samples. Aerobic anoxygenic phototrophic bacteria (AAP) play important roles in carbon and energy cycling in aquatic systems. In oceans, those bacteria are widely distributed; however, their abundance and importance are still poorly understood. The aim of this study was to estimate abundance and diversity of AAPs in metagenomes from an upwelling affected coastal bay in Arraial do Cabo, Brazil, using in silico screening for the anoxygenic photosynthesis core genes. Metagenomes from the Global Ocean Sample Expedition (GOS) were screened for comparative purposes. AAPs were highly abundant in the free-living bacterial fraction from Arraial do Cabo: 23.88% of total bacterial cells, compared with 15% in the GOS dataset. Of the ten most AAP abundant samples from GOS, eight were collected close to the Equator where solar irradiation is high year-round. We were able to assign most retrieved sequences to phylo-groups, with a particularly high abundance of Roseobacter in Arraial do Cabo samples. The high abundance of AAP in this tropical bay may be related to the upwelling phenomenon and subsequent picoplankton bloom. These results suggest a link between upwelling and light abundance and demonstrate AAP even in oligotrophic tropical and subtropical environments. Longitudinal studies in the Arraial do Cabo region are warranted to understand the dynamics of AAP at different locations and seasons, and the ecological role of these unique bacteria for biogeochemical and energy cycling in the ocean. Y1 - 2016 U6 - https://doi.org/10.1089/omi.2015.0142 SN - 1536-2310 SN - 1557-8100 VL - 20 SP - 76 EP - 87 PB - Liebert CY - New Rochelle ER - TY - JOUR A1 - Lischke, Betty A1 - Weithoff, Guntram A1 - Wickham, Stephen A. A1 - Attermeyer, Katrin A1 - Grossart, Hans-Peter A1 - Scharnweber, Inga Kristin A1 - Hilt, Sabine A1 - Gaedke, Ursula T1 - Large biomass of small feeders: ciliates may dominate herbivory in eutrophic lakes JF - Journal of plankton research N2 - The importance of ciliates as herbivores and in biogeochemical cycles is increasingly recognized. An opportunity to observe the potential consequences of zooplankton dominated by ciliates arose when winter fish kills resulted in strong suppression of crustaceans by young planktivorous fish in two shallow lakes. On an annual average, ciliates made up 38-76% of the total zooplankton biomass in both lakes during two subsequent years. Consequently, ciliate biomass and their estimated grazing potential were extremely high compared with other lakes of various trophic states and depths. Grazing estimates based on abundance and size suggest that ciliates should have cleared the water column of small (<5 mu m) and intermediate (5-50 mu m) sized phytoplankton more than once a day. Especially, small feeders within the ciliates were important, likely exerting a strong top-down control on small phytoplankton. Particle-attached bacteria were presumably strongly suppressed by intermediate-sized ciliate feeders. In contrast to other lakes, large phytoplankton was proportionately very abundant. The phytoplankton community had a high evenness, which may be attributed to the feeding by numerous fast growing and selective ciliate species. Our study highlights ciliates as an important trophic link and adds to the growing awareness of the role of winter processes for plankton dynamics. KW - phytoplankton KW - crustaceans KW - rotifers KW - filtration rate KW - winter fish kill Y1 - 2016 U6 - https://doi.org/10.1093/plankt/fbv102 SN - 0142-7873 SN - 1464-3774 VL - 38 SP - 2 EP - 15 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Grossart, Hans-Peter A1 - Wurzbacher, Christian A1 - James, Timothy Y. A1 - Kagami, Maiko T1 - Discovery of dark matter fungi in aquatic ecosystems demands a reappraisal of the phylogeny and ecology of zoosporic fungi JF - Fungal ecology N2 - Our knowledge of zoosporic fungal phylogeny, physiology, and ecological functions, in particular their role in aquatic food web dynamics and biogeochemistry, is limited. The recent discovery of numerous dark matter fungi (DMF), i.e., uncultured and poorly known taxa belonging to early diverging branches of the fungal tree (namely the Rozellomycota and Chytridiomycota) calls for reconsideration of the phylogeny and ecology of zoosporic fungi. In this opinion paper, we summarize the exploration of new, recently discovered lineages of DMF and their implications for the ecology, evolution, and biogeography of the rapidly growing fungal tree. We also discuss possible ecological roles of zoosporic fungi in relation to recent methodological developments including single cell genomics and cultivation efforts. Finally, we suggest linking explorative with experimental research to gain deeper insights into the physiology and ecological functioning of zoosporic fungi DMF in aquatic habitats. (C) 2015 Elsevier Ltd and The British Mycological Society. All rights reserved. KW - Dark matter fungi KW - Zoosporic fungi KW - Fungal tree KW - Chytridiomycota KW - Rozellomycota KW - Fungal physiology and ecology KW - Aquatic habitats Y1 - 2016 U6 - https://doi.org/10.1016/j.funeco.2015.06.004 SN - 1754-5048 SN - 1878-0083 VL - 19 SP - 28 EP - 38 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Izhitskiy, A. S. A1 - Zavialov, P. O. A1 - Sapozhnikov, P. V. A1 - Kirillin, G. B. A1 - Grossart, Hans-Peter A1 - Kalinina, O. Y. A1 - Zalota, A. K. A1 - Goncharenko, I. V. A1 - Kurbaniyazov, A. K. T1 - Present state of the Aral Sea: diverging physical and biological characteristics of the residual basins JF - Scientific reports N2 - Latest data on the hydrophysical and biological state of the residual basins of the Aral Sea are presented and compared. Direct, quasi-simultaneous observations were carried out in the central part of the Western Large Aral Sea, the northern extremity of the Large Aral known as Chernyshev Bay, Lake Tshchebas, and the Small Aral Sea in October 2014. The Large Aral Sea and Lake Tshchebas transformed into hyperhaline water bodies with highly special taxocene structure. The Small Aral Sea was a relatively diverse brackish ecosystem, which was rather similar to the pre-desiccation environment. The Small Aral Sea and Lake Tshchebas exhibited a fully-mixed vertical structure, whereas the Western Large Aral Sea was strongly stratified. Our data show that during desiccation, different parts of the Aral Sea experienced different environmental conditions, resulting in qualitative and quantitative differences in the physical and biological regimes among the different residual basins. Y1 - 2016 U6 - https://doi.org/10.1038/srep23906 SN - 2045-2322 VL - 6 SP - 1435 EP - 1442 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Svanys, Algirdas A1 - Eigemann, Falk A1 - Grossart, Hans-Peter A1 - Hilt, Sabine T1 - Microcystins do not necessarily lower the sensitivity of Microcystis aeruginosa to tannic acid JF - FEMS microbiology letters N2 - Different phytoplankton strains have been shown to possess varying sensitivities towards macrophyte allelochemicals, yet the reasons for this are largely unknown. To test whether microcystin (MC) is responsible for strain-specific sensitivities of Microcystis aeruginosa to macrophyte allelochemicals, we compared the sensitivity of 12 MC- and non-MC-producing M. aeruginosa strains, including an MC-deficient mutant and its wild type, to the polyphenolic allelochemical tannic acid (TA). Non-MC-producing strains showed a significantly higher sensitivity to TA than MC-producing strains, both in Chlorophyll a concentrations and quantum yields of photosystem II. In contrast, an MC-deficient mutant displayed a higher fitness against TA compared to its wild type. These results suggest that the resistance of M. aeruginosa to polyphenolic allelochemicals is not primarily related to MCs per se, but to other yet unknown protective mechanisms related to MCs. KW - allelopathy KW - Delta mcyB mutant KW - microcystin KW - Microcystis aeruginosa KW - tannic acid Y1 - 2016 U6 - https://doi.org/10.1093/femsle/fnv227 SN - 0378-1097 SN - 1574-6968 VL - 363 SP - 53 EP - 77 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Grossart, Hans-Peter A1 - Rojas-Jimenez, Keilor T1 - Aquatic fungi: targeting the forgotten in microbial ecology JF - Current opinion in microbiology N2 - Fungi constitute important and conspicuous components of aquatic microbial communities, but their diversity and functional roles remain poorly characterized. New methods and conceptual frameworks are required to accurately describe their ecological roles, involvement in global cycling processes, and utility for human activities, considering both cultivation independent techniques as well as experiments in laboratory and in natural ecosystems. Here we highlight recent developments and extant knowledge gaps in aquatic mycology, and provide a conceptual model to expose the importance of fungi in aquatic food webs and related biogeochemical processes. Y1 - 2016 U6 - https://doi.org/10.1016/j.mib.2016.03.016 SN - 1369-5274 SN - 1879-0364 VL - 31 SP - 140 EP - 145 PB - Elsevier CY - London ER -