TY  - JOUR
A1  - Bjorneras, C.
A1  - Weyhenmeyer, G. A.
A1  - Evans, C. D.
A1  - Gessner, M. O.
A1  - Großart, Hans-Peter
A1  - Kangur, K.
A1  - Kokorite, I.
A1  - Kortelainen, P.
A1  - Laudon, H.
A1  - Lehtoranta, J.
A1  - Lottig, N.
A1  - Monteith, D. T.
A1  - Noges, P.
A1  - Noges, T.
A1  - Oulehle, F.
A1  - Riise, G.
A1  - Rusak, J. A.
A1  - Raike, A.
A1  - Sire, J.
A1  - Sterling, S.
A1  - Kritzberg, E. S.
T1  - Widespread Increases in Iron Concentration in European and North American Freshwaters
JF  - Global biogeochemical cycles
N2  - Recent reports of increasing iron (Fe) concentrations in freshwaters are of concern, given the fundamental role of Fe in biogeochemical processes. Still, little is known about the frequency and geographical distribution of Fe trends or about the underlying drivers. We analyzed temporal trends of Fe concentrations across 340 water bodies distributed over 10 countries in northern Europe and North America in order to gain a clearer understanding of where, to what extent, and why Fe concentrations are on the rise. We found that Fe concentrations have significantly increased in 28% of sites, and decreased in 4%, with most positive trends located in northern Europe. Regions with rising Fe concentrations tend to coincide with those with organic carbon (OC) increases. Fe and OC increases may not be directly mechanistically linked, but may nevertheless be responding to common regional-scale drivers such as declining sulfur deposition or hydrological changes. A role of hydrological factors was supported by covarying trends in Fe and dissolved silica, as these elements tend to stem from similar soil depths. A positive relationship between Fe increases and conifer cover suggests that changing land use and expanded forestry could have contributed to enhanced Fe export, although increases were also observed in nonforested areas. We conclude that the phenomenon of increasing Fe concentrations is widespread, especially in northern Europe, with potentially significant implications for wider ecosystem biogeochemistry, and for the current browning of freshwaters.
Y1  - 2017
U6  - https://doi.org/10.1002/2017GB005749
SN  - 0886-6236
SN  - 1944-9224
VL  - 31
SP  - 1488
EP  - 1500
PB  - American Geophysical Union
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  - Frenken, Thijs
A1  - Alacid, Elisabet
A1  - Berger, Stella A.
A1  - Bourne, Elizabeth Charlotte
A1  - Gerphagnon, Melanie
A1  - Großart, Hans-Peter
A1  - Gsell, Alena S.
A1  - Ibelings, Bas W.
A1  - Kagami, Maiko
A1  - Kupper, Frithjof C.
A1  - Letcher, Peter M.
A1  - Loyau, Adeline
A1  - Miki, Takeshi
A1  - Nejstgaard, Jens C.
A1  - Rasconi, Serena
A1  - Rene, Albert
A1  - Rohrlack, Thomas
A1  - Rojas-Jimenez, Keilor
A1  - Schmeller, Dirk S.
A1  - Scholz, Bettina
A1  - Seto, Kensuke
A1  - Sime-Ngando, Telesphore
A1  - Sukenik, Assaf
A1  - Van de Waal, Dedmer B.
A1  - Van den Wyngaert, Silke
A1  - Van Donk, Ellen
A1  - Wolinska, Justyna
A1  - Wurzbacher, Christian
A1  - Agha, Ramsy
T1  - Integrating chytrid fungal parasites into plankton ecology: research gaps and needs
JF  - Environmental microbiology
N2  - Chytridiomycota, often referred to as chytrids, can be virulent parasites with the potential to inflict mass mortalities on hosts, causing e.g. changes in phytoplankton size distributions and succession, and the delay or suppression of bloom events. Molecular environmental surveys have revealed an unexpectedly large diversity of chytrids across a wide range of aquatic ecosystems worldwide. As a result, scientific interest towards fungal parasites of phytoplankton has been gaining momentum in the past few years. Yet, we still know little about the ecology of chytrids, their life cycles, phylogeny, host specificity and range. Information on the contribution of chytrids to trophic interactions, as well as co-evolutionary feedbacks of fungal parasitism on host populations is also limited. This paper synthesizes ideas stressing the multifaceted biological relevance of phytoplankton chytridiomycosis, resulting from discussions among an international team of chytrid researchers. It presents our view on the most pressing research needs for promoting the integration of chytrid fungi into aquatic ecology.
Y1  - 2017
U6  - https://doi.org/10.1111/1462-2920.13827
SN  - 1462-2912
SN  - 1462-2920
VL  - 19
SP  - 3802
EP  - 3822
PB  - Wiley
CY  - Hoboken
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  - 
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  - Hornak, Karel
A1  - Kasalicky, Vojtech
A1  - Simek, Karel
A1  - Großart, Hans-Peter
T1  - Strain-specific consumption and transformation of alga-derived dissolved organic matter by members of the Limnohabitans-C and Polynucleobacter-B clusters of Betaproteobacteria
JF  - Environmental microbiology
N2  - We investigated changes in quality and quantity of extracellular and biomass-derived organic matter (OM) from three axenic algae (genera Rhodomonas, Chlamydomonas, Coelastrum) during growth of Limnohabitans parvus, Limnohabitans planktonicus and Polynucleobacter acidiphobus representing important clusters of freshwater planktonic Betaproteobacteria. Total extracellular and biomass-derived OM concentrations from each alga were approximately 20 mg l(-1) and 1 mg l(-1) respectively, from which up to 9% could be identified as free carbohydrates, polyamines, or free and combined amino acids. Carbohydrates represented 54%-61% of identified compounds of the extracellular OM from each alga. In biomass-derived OM of Rhodomonas and Chlamydomonas 71%-77% were amino acids and polyamines, while in that of Coelastrum 85% were carbohydrates. All bacteria grew on alga-derived OM of Coelastrum, whereas only Limnohabitans strains grew on OM from Rhodomonas and Chlamydomonas. Bacteria consumed 24%-76% and 38%-82% of all identified extracellular and biomass-derived OM compounds respectively, and their consumption was proportional to the concentration of each OM compound in the different treatments. The bacterial biomass yield was higher than the total identifiable OM consumption indicating that bacteria also utilized other unidentified alga-derived OM compounds. Bacteria, however, also produced specific OM compounds suggesting enzymatic polymer degradation or de novo exudation.
Y1  - 2017
U6  - https://doi.org/10.1111/1462-2920.13900
SN  - 1462-2912
SN  - 1462-2920
VL  - 19
SP  - 4519
EP  - 4535
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Kettner, Marie Therese
A1  - Rojas-Jimenez, Keilor
A1  - Oberbeckmann, Sonja
A1  - Labrenz, Matthias
A1  - Großart, Hans-Peter
T1  - Microplastics alter composition of fungal communities in aquatic ecosystems
JF  - Environmental microbiology
N2  - Despite increasing concerns about microplastic (MP) pollution in aquatic ecosystems, there is insufficient knowledge on how MP affect fungal communities. In this study, we explored the diversity and community composition of fungi attached to polyethylene (PE) and polystyrene (PS) particles incubated in different aquatic systems in north-east Germany: the Baltic Sea, the River Warnow and a wastewater treatment plant. Based on next generation 18S rRNA gene sequencing, 347 different operational taxonomic units assigned to 81 fungal taxa were identified on PE and PS. The MP-associated communities were distinct from fungal communities in the surrounding water and on the natural substrate wood. They also differed significantly among sampling locations, pointing towards a substrate and location specific fungal colonization. Members of Chytridiomycota, Cryptomycota and Ascomycota dominated the fungal assemblages, suggesting that both parasitic and saprophytic fungi thrive in MP biofilms. Thus, considering the worldwide increasing accumulation of plastic particles as well as the substantial vector potential of MP, especially these fungal taxa might benefit from MP pollution in the aquatic environment with yet unknown impacts on their worldwide distribution, as well as biodiversity and food web dynamics at large.
Y1  - 2017
U6  - https://doi.org/10.1111/1462-2920.13891
SN  - 1462-2912
SN  - 1462-2920
VL  - 19
SP  - 4447
EP  - 4459
PB  - Wiley
CY  - Hoboken
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  - 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 CO2 perturbation on phosphorus pool sizes and uptake in a mesocosm experiment during a low productive summer season in the northern Baltic Sea
JF  - 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.
Y1  - 2016
U6  - https://doi.org/10.5194/bg-13-3035-2016
SN  - 1726-4170
SN  - 1726-4189
VL  - 13
SP  - 3035
EP  - 3050
PB  - Copernicus
CY  - Göttingen
ER  -