@article{AmalfitanoCornoEckertetal.2017, author = {Amalfitano, Stefano and Corno, Gianluca and Eckert, Ester and Fazi, Stefano and Ninio, Shira and Callieri, Cristiana and Grossart, Hans-Peter and Eckert, Werner}, title = {Tracing particulate matter and associated microorganisms in freshwaters}, series = {Hydrobiologia : acta hydrobiologica, hydrographica, limnologica et protistologica}, volume = {800}, journal = {Hydrobiologia : acta hydrobiologica, hydrographica, limnologica et protistologica}, publisher = {Springer}, address = {Dordrecht}, issn = {0018-8158}, doi = {10.1007/s10750-017-3260-x}, pages = {145 -- 154}, year = {2017}, abstract = {Sediment resuspension represents a key process in all natural aquatic systems, owing to its role in nutrient cycling and transport of potential contaminants. Although suspended solids are generally accepted as an important quality parameter, current monitoring programs cover quantitative aspects only. Established methodologies do not provide information on origin, fate, and risks associated with uncontrolled inputs of solids in waters. Here we discuss the analytical approaches to assess the occurrence and ecological relevance of resuspended particulate matter in freshwaters, with a focus on the dynamics of associated contaminants and microorganisms. Triggered by the identification of specific physical-chemical traits and community structure of particle-associated microorganisms, recent findings suggest that a quantitative determination of microorganisms can be reasonably used to trace the origin of particulate matter by means of nucleic acid-based assays in different aquatic systems.}, language = {en} } @article{AttermeyerGrossartFluryetal.2017, author = {Attermeyer, Katrin and Grossart, Hans-Peter and Flury, Sabine and Premke, Katrin}, title = {Bacterial processes and biogeochemical changes in the water body of kettle holes - mainly driven by autochthonous organic matter?}, series = {Aquatic sciences : research across boundaries}, volume = {79}, journal = {Aquatic sciences : research across boundaries}, publisher = {Springer}, address = {Basel}, issn = {1015-1621}, doi = {10.1007/s00027-017-0528-1}, pages = {675 -- 687}, year = {2017}, abstract = {Kettle holes are small inland waters formed from glacially-created depressions often situated in agricultural landscapes. Due to their high perimeter-to-area ratio facilitating a high aquatic-terrestrial coupling, kettle holes can accumulate high concentrations of organic carbon and nutrients, fueling microbial activities and turnover rates. Thus, they represent hotspots of carbon turnover in the landscape, but their bacterial activities and controlling factors have not been well investigated. Therefore, we aimed to assess the relative importance of various environmental factors on bacterial and biogeochemical processes in the water column of kettle holes and to disentangle their variations. In the water body of ten kettle holes in north-eastern Germany, we measured several physico-chemical and biological parameters such as carbon quantity and quality, as well as bacterial protein production (BP) and community respiration (CR) in spring, early summer and autumn 2014. Particulate organic matter served as an indicator of autochthonous production and represented an important parameter to explain variations in BP and CR. This notion is supported by qualitative absorbance indices of dissolved molecules in water samples and C: N ratios of the sediments, which demonstrate high fractions of autochthonous organic matter (OM) in the studied kettle holes. In contrast, dissolved chemical parameters were less important for bacterial activities although they revealed strong differences throughout the growing season. Pelagic bacterial activities and dynamics might thus be regulated by autochthonous OM in kettle holes implying a control of important biogeochemical processes by internal primary production rather than facilitated exchange with the terrestrial surrounding due to a high perimeter-to-area ratio.}, language = {en} } @article{EckertDiCesareKettneretal.2017, author = {Eckert, Ester M. and Di Cesare, Andrea and Kettner, Marie Therese and Arias-Andres, Maria and Fontaneto, Diego and Grossart, Hans-Peter and Corno, Gianluca}, title = {Microplastics increase impact of treated wastewater on freshwater microbial community}, series = {Environmental pollution}, volume = {234}, journal = {Environmental pollution}, publisher = {Elsevier}, address = {Oxford}, issn = {0269-7491}, doi = {10.1016/j.envpol.2017.11.070}, pages = {495 -- 502}, year = {2017}, abstract = {Plastic pollution is a major global concern with several million microplastic particles entering every day freshwater ecosystems via wastewater discharge. Microplastic particles stimulate biofilm formation (plastisphere) throughout the water column and have the potential to affect microbial community structure if they accumulate in pelagic waters, especially enhancing the proliferation of biohazardous bacteria. To test this scenario, we simulated the inflow of treated wastewater into a temperate lake using a continuous culture system with a gradient of concentration of microplastic particles. We followed the effect of microplastics on the microbial community structure and on the occurrence of integrase 1 (intl), a marker associated with mobile genetic elements known as a proxy for anthropogenic effects on the spread of antimicrobial resistance genes. The abundance of intl increased in the plastisphere with increasing microplastic particle concentration, but not in the water surrounding the microplastic particles. Likewise, the microbial community on microplastic was more similar to the original wastewater community with increasing microplastic concentrations. Our results show that microplastic particles indeed promote persistence of typical indicators of microbial anthropogenic pollution in natural waters, and substantiate that their removal from treated wastewater should be prioritised. (C) 2017 Elsevier Ltd. All rights reserved.}, language = {en} } @article{FerreraSarmentoPriscuetal.2017, author = {Ferrera, Isabel and Sarmento, Hugo and Priscu, John C. and Chiuchiolo, Amy and Gonzalez, Jose M. and Grossart, Hans-Peter}, title = {Diversity and Distribution of Freshwater Aerobic Anoxygenic Phototrophic Bacteria across a Wide Latitudinal Gradient}, series = {Frontiers in microbiology}, volume = {8}, journal = {Frontiers in microbiology}, publisher = {Frontiers Research Foundation}, address = {Lausanne}, issn = {1664-302X}, doi = {10.3389/fmicb.2017.00175}, pages = {12}, year = {2017}, abstract = {Aerobic anoxygenic phototrophs (AAPs) have been shown to exist in numerous marine and brackish environments where they are hypothesized to play important ecological roles. Despite their potential significance, the study of freshwater AAPs is in its infancy and limited to local investigations. Here, we explore the occurrence, diversity and distribution of AAPs in lakes covering a wide latitudinal gradient: Mongolian and German lakes located in temperate regions of Eurasia, tropical Great East African lakes, and polar permanently ice-covered Antarctic lakes. Our results show a widespread distribution of AAPs in lakes with contrasting environmental conditions and confirm that this group is composed of different members of the Alpha- and Betaproteobacteria. While latitude does not seem to strongly influence AAP abundance, clear patterns of community structure and composition along geographic regions were observed as indicated by a strong macro-geographical signal in the taxonomical composition of AAPs. Overall, our results suggest that the distribution patterns of freshwater AAPs are likely driven by a combination of small-scale environmental conditions (specific of each lake and region) and large-scale geographic factors (climatic regions across a latitudinal gradient).}, language = {en} } @article{GilingNejstgaardBergeretal.2017, author = {Giling, Darren P. and Nejstgaard, Jens C. and Berger, Stella A. and Grossart, Hans-Peter and Kirillin, Georgiy and Penske, Armin and Lentz, Maren and Casper, Peter and Sareyka, Joerg and Gessner, Mark O.}, title = {Thermocline deepening boosts ecosystem metabolism: evidence from a large-scale lake enclosure experiment simulating a summer storm}, series = {Global change biology}, volume = {23}, journal = {Global change biology}, publisher = {Wiley}, address = {Hoboken}, issn = {1354-1013}, doi = {10.1111/gcb.13512}, pages = {1448 -- 1462}, year = {2017}, abstract = {Extreme weather events can pervasively influence ecosystems. Observations in lakes indicate that severe storms in particular can have pronounced ecosystem-scale consequences, but the underlying mechanisms have not been rigorously assessed in experiments. One major effect of storms on lakes is the redistribution of mineral resources and plankton communities as a result of abrupt thermocline deepening. We aimed at elucidating the importance of this effect by mimicking in replicated large enclosures (each 9 m in diameter, ca. 20 m deep, ca. 1300 m 3 in volume) a mixing event caused by a severe natural storm that was previously observed in a deep clear-water lake. Metabolic rates were derived from diel changes in vertical profiles of dissolved oxygen concentrations using a Bayesian modelling approach, based on high-frequency measurements. Experimental thermocline deepening stimulated daily gross primary production (GPP) in surface waters by an average of 63\% for > 4 weeks even though thermal stratification re-established within 5 days. Ecosystem respiration (ER) was tightly coupled to GPP, exceeding that in control enclosures by 53\% over the same period. As GPP responded more strongly than ER, net ecosystem productivity (NEP) of the entire water column was also increased. These protracted increases in ecosystem metabolism and autotrophy were driven by a proliferation of inedible filamentous cyanobacteria released from light and nutrient limitation after they were entrained from below the thermocline into the surface water. Thus, thermocline deepening by a single severe storm can induce prolonged responses of lake ecosystem metabolism independent of other storm-induced effects, such as inputs of terrestrial materials by increased catchment run-off. This highlights that future shifts in frequency, severity or timing of storms are an important component of climate change, whose impacts on lake thermal structure will superimpose upon climate trends to influence algal dynamics and organic matter cycling in clear-water lakes. Keywords: climate variability, ecosystem productivity, extreme events, gross primary production, mesocosm, respiration stratified lakes}, language = {en} } @article{GilingStaehrGrossartetal.2017, author = {Giling, Darren P. and Staehr, Peter A. and Grossart, Hans-Peter and Andersen, Mikkel Rene and Boehrer, Bertram and Escot, Carmelo and Evrendilek, Fatih and Gomez-Gener, Lluis and Honti, Mark and Jones, Ian D. and Karakaya, Nusret and Laas, Alo and Moreno-Ostos, Enrique and Rinke, Karsten and Scharfenberger, Ulrike and Schmidt, Silke R. and Weber, Michael and Woolway, R. Iestyn and Zwart, Jacob A. and Obrador, Biel}, title = {Delving deeper: Metabolic processes in the metalimnion of stratified lakes}, series = {Limnology and oceanography}, volume = {62}, journal = {Limnology and oceanography}, publisher = {Wiley}, address = {Hoboken}, issn = {0024-3590}, doi = {10.1002/lno.10504}, pages = {1288 -- 1306}, year = {2017}, abstract = {Many lakes exhibit seasonal stratification, during which they develop strong thermal and chemical gradients. An expansion of depth-integrated monitoring programs has provided insight into the importance of organic carbon processing that occurs below the upper mixed layer. However, the chemical and physical drivers of metabolism and metabolic coupling remain unresolved, especially in the metalimnion. In this depth zone, sharp gradients in key resources such as light and temperature co-occur with dynamic physical conditions that influence metabolic processes directly and simultaneously hamper the accurate tracing of biological activity. We evaluated the drivers of metalimnetic metabolism and its associated uncertainty across 10 stratified lakes in Europe and North America. We hypothesized that the metalimnion would contribute highly to whole-lake functioning in clear oligotrophic lakes, and that metabolic rates would be highly variable in unstable polymictic lakes. Depth-integrated rates of gross primary production (GPP) and ecosystem respiration (ER) were modelled from diel dissolved oxygen curves using a Bayesian approach. Metabolic estimates were more uncertain below the epilimnion, but uncertainty was not consistently related to lake morphology or mixing regime. Metalimnetic rates exhibited high day-to-day variability in all trophic states, with the metalimnetic contribution to daily whole-lake GPP and ER ranging from 0\% to 87\% and < 1\% to 92\%, respectively. Nonetheless, the metalimnion of low-nutrient lakes contributed strongly to whole-lake metabolism on average, driven by a collinear combination of highlight, low surface-water phosphorous concentration and high metalimnetic volume. Consequently, a single-sensor approach does not necessarily reflect whole-ecosystem carbon dynamics in stratified lakes.}, language = {en} } @article{HornickBachCrawfurdetal.2017, author = {Hornick, Thomas and Bach, Lennart T. and Crawfurd, Katharine J. and Spilling, Kristian and Achterberg, Eric P. and Woodhouse, Jason Nicholas and Schulz, Kai G. and Brussaard, Corina P. D. and Riebesell, Ulf and Grossart, Hans-Peter}, title = {Ocean acidification impacts bacteria-phytoplankton coupling at low-nutrient conditions}, series = {Biogeosciences}, volume = {14}, journal = {Biogeosciences}, number = {1}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1726-4170}, doi = {10.5194/bg-14-1-2017}, pages = {1 -- 15}, year = {2017}, abstract = {The oceans absorb about a quarter of the annually produced anthropogenic atmospheric carbon dioxide (CO2), resulting in a decrease in surface water pH, a process termed ocean acidification (OA). Surprisingly little is known about how OA affects the physiology of heterotrophic bacteria or the coupling of heterotrophic bacteria to phytoplankton when nutrients are limited. Previous experiments were, for the most part, undertaken during productive phases or following nutrient additions designed to stimulate algal blooms. Therefore, we performed an in situ large-volume mesocosm (similar to 55 m(3)) experiment in the Baltic Sea by simulating different fugacities of CO2 (fCO(2)) extending from present to future conditions. The study was conducted in July-August after the nominal spring bloom, in order to maintain low-nutrient conditions throughout the experiment. This resulted in phytoplankton communities dominated by small-sized functional groups (picophytoplankton). There was no consistent fCO(2)-induced effect on bacterial protein production (BPP), cell-specific BPP (csBPP) or biovolumes (BVs) of either free-living (FL) or particle-associated (PA) heterotrophic bacteria, when considered as individual components (univariate analyses). Permutational Multivariate Analysis of Variance (PERMANOVA) revealed a significant effect of the fCO(2) treatment on entire assemblages of dissolved and particulate nutrients, metabolic parameters and the bacteria-phytoplankton community. However, distance-based linear modelling only identified fCO(2) as a factor explaining the variability observed amongst the microbial community composition, but not for explaining variability within the metabolic parameters. This suggests that fCO(2) impacts on microbial metabolic parameters occurred indirectly through varying physicochemical parameters and microbial species composition. Cluster analyses examining the co-occurrence of different functional groups of bacteria and phytoplankton further revealed a separation of the four fCO(2)-treated mesocosms from both control mesocosms, indicating that complex trophic interactions might be altered in a future acidified ocean. Possible consequences for nutrient cycling and carbon export are still largely unknown, in particular in a nutrient-limited ocean.}, language = {en} } @article{IonescuBizicIonescuDeMaioetal.2017, author = {Ionescu, Danny and Bizic-Ionescu, Mina and De Maio, Nicola and Cypionka, Heribert and Grossart, Hans-Peter}, title = {Community-like genome in single cells of the sulfur bacterium Achromatium oxaliferum}, series = {Nature Communications}, volume = {8}, journal = {Nature Communications}, publisher = {Nature Publ. Group}, address = {London}, issn = {2041-1723}, doi = {10.1038/s41467-017-00342-9}, pages = {9193 -- 9205}, year = {2017}, language = {en} } @misc{KalinkatCabralDarwalletal.2017, author = {Kalinkat, Gregor and Cabral, Juliano Sarmento and Darwall, William and Ficetola, G. Francesco and Fisher, Judith L. and Giling, Darren P. and Gosselin, Marie-Pierre and Grossart, Hans-Peter and Jaehnig, Sonja C. and Jeschke, Jonathan M. and Knopf, Klaus and Larsen, Stefano and Onandia, Gabriela and Paetzig, Marlene and Saul, Wolf-Christian and Singer, Gabriel and Sperfeld, Erik and Jaric, Ivan}, title = {Flagship umbrella species needed for the conservation of overlooked aquatic biodiversity}, series = {Conservation biology : the journal of the Society for Conservation Biology}, volume = {31}, journal = {Conservation biology : the journal of the Society for Conservation Biology}, publisher = {Wiley}, address = {Hoboken}, issn = {0888-8892}, doi = {10.1111/cobi.12813}, pages = {481 -- 485}, year = {2017}, language = {en} } @article{LauHupferGrossart2017, author = {Lau, Maximilian P. and Hupfer, Michael and Grossart, Hans-Peter}, title = {Reduction-oxidation cycles of organic matter increase bacterial activity in the pelagic oxycline}, series = {Environmental microbiology reports}, volume = {9}, journal = {Environmental microbiology reports}, publisher = {Wiley}, address = {Hoboken}, issn = {1758-2229}, doi = {10.1111/1758-2229.12526}, pages = {257 -- 267}, year = {2017}, abstract = {Dissolved organic matter (DOM) in aquatic ecosystems contains redox-active moieties, which are prone to oxidation and reduction reactions. Oxidized moieties feature reduction potentials E-h, so that the moieties may be used as terminal electron acceptors (TEAs) in microbial respiration with a thermodynamic energy yield between nitrate and sulfate reduction. Here, we study the response of pelagic freshwater bacteria to exposure to native DOM with varying availabilities of oxidized moieties and hence redox state. Our results show that the prevalence of oxidized DOM favors microbial production and growth in anoxic waters. Reduced DOM in stratified lakes may be oxidized when fluctuations of the oxycline expose DOM in previously anoxic water to epilimnetic oxygen. The resulting oxidized DOM may be rapidly used as TEAs in microbial respiration during subsequent periods of anoxia. We further investigate if the prevalence of these organic electron sinks in anaerobic incubations can induce changes in the microbial community. Our results reveal that DOM traversing transient redox interfaces selects for species that profit from such spatially confined and cyclically restored TEA reservoirs.}, language = {en} }